tag:blogger.com,1999:blog-83412190170396610172024-03-21T09:54:34.481-07:00e - AptitudeThe aim of this blog is develop the students aptitude skills. This Blog Contains all the aptitude questions and answers. And it contains Famous companies interview question papersVijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.comBlogger35125tag:blogger.com,1999:blog-8341219017039661017.post-82589738646070633532012-10-02T04:58:00.001-07:002012-10-02T04:58:41.637-07:00Java Interview Question and Answers<table border="0" cellpadding="3" cellspacing="0" style="width: 625px;"><tbody>
<tr><td align="left" bgcolor="#6388e5" nowrap="nowrap" valign="top" width="65"><span style="font-family: Verdana; font-size: xx-small;"><strong>Questions : 1</strong></span></td>
<td bgcolor="#6388e5"><strong>What is JVM (Java Virtual Machine) ? </strong></td>
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JVM stands for Java Virtual Machine. It’s an abstract
computer or virtual computer which
runs the compiled java programs. Actually JVM is a software
implementation which stands
on the top of the real hardware platform and operating system. It
provides abstraction
between the compiled java program and the hardware and operating system.
So the compiled program does not have to worry about what hardware and
operating
system he has to run in, it’s all handled by the JVM and thus attaining
portability. All Java
programs are compiled in to bytecodes. JVM can only understand and
execute Java
bytecodes. we can visualize Java bytecodes as machine language for JVM.
Java compiler
takes the .java files and compiles it to a “bytecode” file with .class
file extension. Compiler
generates one class file for one source file.
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<td bgcolor="#6388e5"><strong>What is JIT (Just-in-Time) Compilation ?
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When JVM compiles the class file he does not compile
the full class file in one shot. Compilation is done on function basis or file basis. Advantage
gained from this is that heavy parsing of original source code is avoided. Depending on
need basis the compilation is done. This typ of compilation is termed as JIT or Just-in-
Time compilation.
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<td bgcolor="#6388e5"><strong>How do you implement inheritance in Java?
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nheritance is implemented by using
“EXTEND” keyword. </div>
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<td align="left" bgcolor="#6388e5" nowrap="nowrap" valign="top" width="65"><strong>Questions : 4</strong></td>
<td bgcolor="#6388e5"><strong>How can we implement polymorphism in Java ?<br />
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Polymorphism is the capability of an action or method to do different things based on the
object that it is acting upon. There are two types of polymorphism:-
<br /> Method Polymorphism through overloading.
<br /> Object polymorphism by inheritance / interfaces.</div>
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<td bgcolor="#6388e5"><strong>What are packages ?
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Packages group related classes and interfaces together and thus avoiding any name conflicts.
From OOP’s point of view packages are useful for grouping related classes together.
Classes are group together in a package using “package” keyword.</div>
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<td bgcolor="#6388e5"><strong>What is the use if “instanceof” keyword ?
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“ instanceof ” keyword is used to check what is the type of object. F
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<td bgcolor="#6388e5"><strong>What are Native methods in Java ?
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There may be times when we want to call subroutines which are written in some other
language other than Java like C++, VB6 etc.
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<td bgcolor="#6388e5"><strong>Explain in depth Garbage collector ?
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Garbage collection is the process of automatically freeing objects that are no longer
referenced by the program. This frees the programmer from having to keep track of when
to free allocated memory, thereby preventing many potential bugs. Thus making
programmers more productive as they can now put more effort in coding rather than
worrying about memory management. </div>
<div align="justify">
The only disadvantage of garbage collector is it adds overheads. Because
the JVM (Java
virtual machine) has to keep a constant track of the objects which are
not referenced and
then free these unreferenced objects on fly. This whole process has a
slight impact on the
application performance. But garbage collector has a good algorithm and
it runs in its own thread thus having a least impact on the application
performance but still it has
some impact. </div>
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<td bgcolor="#6388e5"><strong>How can we force the garbage collector to run?
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Garbage collector can be run forcibly using “System.gc()” or “Runtime.gc()”
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What’s the use of JAVAP tool ?
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javap disassembles compiled Java files and spits out representation of the Java program.
This is a useful option when the original source code is not available.
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<td align="left" bgcolor="#6388e5" nowrap="nowrap" valign="top" width="65"><strong>Questions : 11</strong></td>
<td bgcolor="#6388e5"><strong>What are applets ?
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Applets are small applications that are accessed from web server automatically installed,
and run from the browser. Once an applet arrives on the client it has limited access to
resources thus ensuring security for the end user. An applet is controlled by the software
that runs it. Usually, the underlying software is a browser, but it can also be applet viewer.
If you run the applet source code from eclipse it runs inside an applet viewer. All applets
should inherit from applet class.
<br />
Below are sequences of events which occur in applet:-
The <b>init Method: </b>The init method is called when the applet is first loaded. Init method
can be used to initialize color, fonts or any type of one type operation needed for the
applet.<br />
The <b>start Method:</b> The start method is called when user visits a browser with an applet on
it. In start method applet spawns a thread in which it runs the paint method.<br />
<b>paint()</b> is called every time when applet has to re-display everything. paint() event can
occur due to various reasons some of the reasons are :-.
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<td bgcolor="#6388e5"><strong>In which package is the applet class located?
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Applet classes are located in " java.applet "package.
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<td bgcolor="#6388e5"><strong>How can you copy one array in to a different array?
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System.arraycopy(myOldArray, 0, myNewArray, 0, length);+
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<td align="left" bgcolor="#6388e5" nowrap="nowrap" valign="top" width="65"><strong>Questions : 14</strong></td>
<td bgcolor="#6388e5"><strong>Can you explain the core collection interfaces?
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There are six interfaces and come under two different inheritance group one which comes
under the collection interface root and the other in the map interface root. </div>
<div align="justify">
Collection<br />
It’s the base of all collection classes. It provides a unified way to manipulate collection
objects. Collection has group of object called as elements. These elements can be accessed
and manipulated using Iterator.
List<br />
In List interface the elements are arranged sequentially. Elements can be inserted in to
any location and you can also insert duplicate elements. In order to access the elements
you need to use the “ListIterator”. Using “ListIterator” you can move back and forth
which makes it unique as compared to other iterators.<br />
Set<br />
It represents a collection but no duplicates are allowed in this case.<br />
SortedSet<br />
It extends the Set interface and sorts the set in ascending order.<br />
Map<br />
Map stores association between keys and value pairs. So given a key you can easily find
the value. One thing important to note is they do not implement iterable interface. But
yes you can obtain a collection view of the map which allows you loop using for loop.<br />SortedMap<br />
t Extends Map so that the keys are maintained in ascending order. </div>
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<td bgcolor="#6388e5"><strong>what’s the main difference between ArrayList / HashMap and Vector /
Hashtable?
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Vector / HashTable are synchronized which means they are thread safe.
Cost of thread
safe is performance degradation. So if you are sure that you are not
dealing with huge number of threads then you should use ArrayList /
HashMap.But yes you can still<br />
synchronize List and Map’s using Collections provided methods :-<br />
List OurList = Collections.synchronizedList (OurList);<br />
Map OurMap = Collections.synchronizedMap (OurMap); </div>
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<td bgcolor="#6388e5"><strong>what is a StringBuffer class and how does it differs from String class?
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StringBuffer is a peer class of String that provides almost all functionality of strings.
String represents fixed-length, immutable character sequences. Comparatively StringBuffer
represents mutable, growable and writeable character sequences. But StringBuffer does
not create new instances as string so it’s more efficient when it comes to intensive concatenation operation.
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<td bgcolor="#6388e5"><strong> What is JAVAdoc utility?
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Javadoc parses comments in JAVA source files and produced HTML pages for the same.
Below is the syntax for the same
javadoc [ options ] [ packagenames ] [ sourcefiles ] [ @files ]
Arguments can be in any order.
Options Command-line options that is doctitle, windowtitle, header, bottom etc<br />
Packagenames: - <br />A series of names of packages, separated by spaces, such as java.lang
java.lang.reflect java.awt. You must separately specify each package you want to
document. Javadoc uses -sourcepath to look for these package names. Javadoc does not
recursively traverse subpackages.<br />
sourcefiles :- <br />A series of source file names, separated by spaces, each of which can begin
with a path and contain a wildcard such as asterisk (*). The path that precedes the source
file name determines where javadoc will look for it. (Javadoc does not use -sourcepath to
look for these source file names.)<br />
@files: - One or more files that contain packagenames and sourcefiles in any order, one
name per line.
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<td align="left" bgcolor="#6388e5" nowrap="nowrap" valign="top" width="65"><strong>Questions : 18</strong></td>
<td bgcolor="#6388e5"><strong>How much subclasses you can maximum in Inheritance?
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In one of our old JAVA projects we had an inheritance depth of five. Believe us we never
liked that code. It’s bad to have a huge inheritance depth. A maintainable inheritance
depth should be maximum 5. Anything above that is horrible. There is no limit as such
specified anywhere that there is some limit on the inheritance sub classing . But depending on environments you
will get stack over flow error.
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Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-81990692309456974912012-03-11T23:03:00.000-07:002012-03-11T23:03:58.200-07:00CORE JAVA QUESTIONS - Part II<div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Can an anonymous class be declared as implementing an interface and extending a class?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;"> An anonymous class may implement an interface or extend a superclass, but may not be declared to do both.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the range of the short type?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">T</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">he range of the short type is -(2^15) to 2^15 - 1.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the range of the char type?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The range of the char type is 0 to 2^16 - 1.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><a name='more'></a><br />
<div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the purpose of finalization?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The purpose of finalization is to give an unreachable object the opportunity to perform any cleanup processing before the object is garbage collected.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What invokes a thread's run() method?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">After a thread is started, via its start() method or that of the Thread class, the JVM invokes the thread's run() method when the thread is initially executed.<br />
<br />
<b>What is the difference between the Boolean & operator and the && operator?<o:p></o:p></b></span></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">If an expression involving the Boolean & operator is evaluated, both operands are evaluated. Then the & operator is applied to the operand. When an expression involving the && operator is evaluated, the first operand is evaluated. If the first operand returns a value of true then the second operand is evaluated. The && operator is then applied to the first and second operands. If the first operand evaluates to false, the evaluation of the second operand is skipped.<br />
<!--[if !supportLineBreakNewLine]--><br />
<!--[endif]--><o:p></o:p></span></div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the purpose of the Runtime class?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The purpose of the Runtime class is to provide access to the Java runtime system.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">How many times may an object's finalize() method be invoked by the <br />
</span></b><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">garbage collector?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">An object's finalize() method may only be invoked once by the garbage collector.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the purpose of the finally clause of a try-catch-finally statement?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The finally clause is used to provide the capability to execute code no matter whether or not an exception is thrown or caught.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the argument type of a program's main() method?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">A program's main() method takes an argument of the String[] type.<br />
<!--[if !supportLineBreakNewLine]--><br />
<!--[endif]--><o:p></o:p></span></div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Which Java operator is right associative?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The = operator is right associative.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the Locale class?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the difference between a break statement and a continue statement?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">A break statement results in the termination of the statement to which it applies (switch, for, do, or while). A continue statement is used to end the current loop iteration and return control to the loop statement.<br />
<!--[if !supportLineBreakNewLine]--><br />
<!--[endif]--><o:p></o:p></span></div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What must a class do to implement an interface?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">It must provide all of the methods in the interface and identify the interface in its implements clause.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What method is invoked to cause an object to begin executing as a separate thread?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The start() method of the Thread class is invoked to cause an object to begin executing as a separate thread.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="color: red; font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the advantage of the event-delegation model over the earlier event-inheritance model? <o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="color: red; font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The event-delegation model has two advantages over the event-inheritance model. First, it enables event handling to be handled by objects other than the ones that generate the events (or their containers). This allows a clean separation between a component's design and its use. The other advantage of the event-delegation model is that it performs much better in applications where many events are generated. This performance improvement is due to the fact that the event-delegation model does not have to repeatedly process unhandled events, as is the case of the event-inheritance</span><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;"><br />
<!--[if !supportLineBreakNewLine]--><br />
<!--[endif]--><o:p></o:p></span></div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">How are commas used in the initialization and iteration parts of a for statement?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Commas are used to separate multiple statements within the initialization and iteration parts of a for statement.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the purpose of the wait(), notify(), and notifyAll() methods?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The wait(),notify(), and notifyAll() methods are used to provide an efficient way for threads to wait for a shared resource. When a thread executes an object's wait() method, it enters the waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods.<br />
<!--[if !supportLineBreakNewLine]--><br />
<!--[endif]--><o:p></o:p></span></div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the difference between the String and StringBuffer classes?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">String objects are constants. StringBuffer objects are not.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the Dictionary class?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The Dictionary class provides the capability to store key-value pairs.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">How is rounding performed under integer division?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The fractional part of the result is truncated. This is known as rounding toward zero.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">For which statements does it make sense to use a label?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The only statements for which it makes sense to use a label are those statements that can enclose a break or continue statement.<br />
<!--[if !supportLineBreakNewLine]--><br />
<!--[endif]--><o:p></o:p></span></div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What restrictions are placed on the values of each case of a switch statement?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">During compilation, the values of each case of a switch statement must evaluate to a value that can be promoted to an int value.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the difference between a while statement and a do statement?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">A while statement checks at the beginning of a loop to see whether the next loop iteration should occur. A do statement checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the body of a loop at least once.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">How does multithreading take place on a computer with a single CPU?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The operating system's task scheduler allocates execution time to multiple tasks. By quickly switching between executing tasks, it creates the impression that tasks execute sequentially.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">How is it possible for two String objects with identical values not to be equal under the == operator?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The == operator compares two objects to determine if they are the same object in memory. It is possible for two String objects to have the same value, but located indifferent areas of memory.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What are the legal operands of the instanceof operator?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The left operand is an object reference or null value and the right operand is a class, interface, or array type.<br />
<!--[if !supportLineBreakNewLine]--><br />
<!--[endif]--><o:p></o:p></span></div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is your platform's default character encoding?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">If you are running Java on English Windows platforms, it is probably Cp1252. If you are running Java on English Solaris platforms, it is most likely 8859_1..<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is a compilation unit?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">A compilation unit is a Java source code file.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What restrictions are placed on method overriding?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Overridden methods must have the same name, argument list, and return type. <br />
The overriding method may not limit the access of the method it overrides. <br />
The overriding method may not throw any exceptions that may not be thrown <br />
by the overridden method.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What are three ways in which a thread can enter the waiting state?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">A thread can enter the waiting state by invoking its sleep() method, by blocking on I/O, by unsuccessfully attempting to acquire an object's lock, or by invoking an object's wait() method. It can also enter the waiting state by invoking its <br />
(deprecated) suspend() method.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the ResourceBundle class?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The ResourceBundle class is used to store locale-specific resources that can be loaded by a program to tailor the program's appearance to the particular locale in which it is being run.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the purpose of a statement block?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">A statement block is used to organize a sequence of statements as a single statement group.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Can an unreachable object become reachable again?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">An unreachable object may become reachable again. This can happen when the object's finalize() method is invoked and the object performs an operation which causes it to become accessible to reachable objects.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What are synchronized methods and synchronized statements?<br />
</span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement<o:p></o:p></span></div>Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-81899990979609187392012-03-11T22:59:00.000-07:002012-03-11T22:59:24.259-07:00CORE JAVA QUESTIONS<div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">What is the difference between an Interface and an Abstract class?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> An abstract class can have instance methods that implement a default behavior. An Interface can only declare constants and instance methods, but cannot implement default behavior and all methods are implicitly abstract. An interface has all public members and no implementation. An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract methods.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">What is the purpose of garbage collection in Java, and when is it used?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> The purpose of garbage collection is to identify and discard objects that are no longer needed by a program so that their resources can be reclaimed and reused. A Java object is subject to garbage collection when it becomes unreachable to the program in which it is used.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><a name='more'></a><br />
<div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">Describe synchronization in respect to multithreading.<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared variable while another thread is in the process of using or updating same shared variable. This usually leads to significant errors.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">Explain different way of using thread?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> The thread could be implemented by using runnable interface or by inheriting from the Thread class. The former is more advantageous, because when you are going for multiple inheritance, the only interface can help.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">What are passby reference and passby value?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> Passby reference means the passing the address itself rather than passing the value. Passby Value means passing a copy of the value to be passed. <o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">What is the difference between a constructor and a method?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> A constructor is a member function of a class that is used to create objects of that class. It has the same name as the class itself, has no return type, and is invoked using the new operator.<o:p></o:p></span></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">A method is an ordinary member function of a class. It has its own name, a return type (which may be void), and is invoked using the dot operator.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">State the significance of public, private, protected, default modifiers both singly and in combination and state the effect of package relationships on declared items qualified by these modifiers.<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> public : Public class is visible in other packages, field is visible everywhere (class must be public too)<o:p></o:p></span></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">private : Private variables or methods may be used only by an instance of the same class that declares the variable or method, A private feature may only be accessed by the class that owns the feature.<o:p></o:p></span></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">protected : Is available to all classes in the same package and also available to all subclasses of the class that owns the protected feature.This access is provided even to subclasses that reside in a different package from the class that owns the protected feature.<o:p></o:p></span></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">default :What you get by default ie, without any access modifier (ie, public private or protected).It means that it is visible to all within a particular package.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">What is an abstract class?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> Abstract class must be extended/subclassed (to be useful). It serves as a template. A class that is abstract may not be instantiated (ie, you may not call its constructor), abstract class may contain static data. Any class with an abstract method is automatically abstract itself, and must be declared as such.<o:p></o:p></span></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">A class may be declared abstract even if it has no abstract methods. This prevents it from being instantiated.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">What is static in java?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> Static means one per class, not one for each matter object no how many instance of a class might exist. This means that you can use them without creating an instance of a class.Static methods are implicitly final, because overriding is done based on the type of the object, and static methods are attached to a class, not an object. A static method in a superclass can be shadowed by another static method in a subclass, as long as the original method was not declared final. However, you can't override a static method with a nonstatic method. In other words, you can't change a static method into an instance method in a subclass.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">What is final?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> A final class can't be extended ie., final class may not be sub classed. A final method can't be overridden when its class is inherited. You can't change value of a final variable (is a constant).<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">What is the GregorianCalendar class?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> The GregorianCalendar provides support for traditional Western calendars<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">What is the Locale class?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region .<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">What is the SimpleTimeZone class?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> The SimpleTimeZone class provides support for a Gregorian calendar .<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">What is the highest-level event class of the event-delegation model?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> The java.util.EventObject class is the highest-level class in the event-delegation class hierarchy.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;">What is an enumeration?<o:p></o:p></span></b></div><div class="MsoNormal"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt;"> An enumeration is an interface containing methods for accessing the underlying data structure from which the enumeration is obtained. It is a construct which collection classes return when you request a collection of all the objects stored in the collection. It allows sequential access to all the elements stored in the collection</span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is a transient variable?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">A transient variable is a variable that may not be serialized.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Why do threads block on I/O?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Threads block on I/O (that is enters the waiting state) so that other threads may execute while the I/O Operation is performed.<br />
<!--[if !supportLineBreakNewLine]--><br />
<!--[endif]--><o:p></o:p></span></div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">How are Observer and Observable used?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.</span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Can a lock be acquired on a class?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Yes, a lock can be acquired on a class. This lock is acquired on the class's Class object.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the preferred size of a component? <o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The preferred size of a component is the minimum component size that will allow the component to display normally.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What state does a thread enter when it terminates its processing?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">When a thread terminates its processing, it enters the dead state.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">How does Java handle integer overflows and underflows?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What modifiers may be used with an inner class that is a member of an outer class?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">A (non-local) inner class may be declared as public, protected, private, static, final, or abstract.<br />
<br />
<b>What is the difference between the >> and >>> operators?<o:p></o:p></b></span></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The >> operator carries the sign bit when shifting right. The >>> zero-fills bits that have been shifted out.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Unicode requires 16 bits and ASCII require 7 bits. Although the ASCII character set uses only 7 bits, it is usually represented as 8 bits. UTF-8 represents characters using 8, 16, and 18 bit patterns. UTF-16 uses 16-bit and larger bit patterns.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the difference between yielding and sleeping?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">When a task invokes its yield() method, it returns to the ready state. When a task invokes its sleep() method, it returns to the waiting state.<br />
<br />
<b>What are wrapper classes?<o:p></o:p></b></span></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Wrapper classes are classes that allow primitive types to be accessed as objects.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Does garbage collection guarantee that a program will not run out of memory?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Garbage collection does not guarantee that a program will not run out of memory. It is possible for programs to use up memory resources faster than they are garbage collected. It is also possible for programs to create objects that are not subject to garbage collection.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What restrictions are placed on the location of a package statement within a source code file?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">A package statement must appear as the first line in a source code file (excluding blank lines and comments).<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Can an object's finalize() method be invoked while it is reachable?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">An object's finalize() method cannot be invoked by the garbage collector while the object is still reachable. However, an object's finalize() method may be invoked by other objects.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the difference between preemptive scheduling and time slicing? </span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Under preemptive scheduling, the highest priority task executes until it enters the waiting or dead states or a higher priority task comes into existence. Under time slicing, a task executes for a predefined slice of time and then reenters the pool of ready tasks. The scheduler then determines which task should execute next, based on priority and other factors.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What value does readLine() return when it has reached the end of a file?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The readLine() method returns null when it has reached the end of a file.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is a native method?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">A native method is a method that is implemented in a language other than Java.<br />
<!--[if !supportLineBreakNewLine]--><br />
<!--[endif]--><o:p></o:p></span></div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Can a for statement loop indefinitely?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Yes, a for statement can loop indefinitely. For example, consider the following: for(;;) ;<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What are order of precedence and associativity, and how are they used? </span></b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">Order of precedence determines the order in which operators are evaluated in expressions. Associatity determines whether an expression is evaluated left-to-right or right-to-left<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">To what value is a variable of the String type automatically initialized?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">The default value of a String type is null.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is the catch or declare rule for method declarations?<o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">If a checked exception may be thrown within the body of a method, the method must either catch the exception or declare it in its throws clause.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">What is a task's priority and how is it used in scheduling? <o:p></o:p></span></b></div><div class="MsoNormal" style="text-indent: .5in;"><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">A task's priority is an integer value that identifies the relative order in which it should be executed with respect to other tasks. The scheduler attempts to schedule higher priority tasks before lower priority tasks.<o:p></o:p></span></div><div class="MsoNormal"><br />
</div><div class="MsoNormal"><b><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-bidi-font-family: Arial;">When a thread is created and started, what is its initial state?<o:p></o:p></span></b></div><span style="font-family: "Verdana","sans-serif"; font-size: 10.0pt; mso-ansi-language: EN-US; mso-bidi-font-family: Arial; mso-bidi-language: AR-SA; mso-fareast-font-family: "Times New Roman"; mso-fareast-language: EN-US;">A thread is in the ready state after it has been created and started.</span>Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-89838025102775225852011-04-14T21:44:00.000-07:002011-04-14T21:44:24.318-07:00Satyam (Mathematic, English) Interview QuestionsLatest Sample Placement Paper Of Satyam For Year-2009-10 (Mathematic, English)<br />
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1.What will come in place of question mark (?) in the following equation? of 168 ? 15 ÷ 5 + ? = 549 ÷ 9 + 2351) 189<br />
2) 107<br />
3) 174<br />
4) 296<br />
5) None of these<br />
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2. Four of the following five parts numbered (1), (2), (3), (4), and (5) are exactly equal.Which part is not equal to the other four parts? The number of that part is your answer.<br />
1) 2x (x + 5) + 12<br />
2) 2x (x + 3) + 3 (x + 4) + x<br />
3) (x + 3)2 + (x + 1) (x + 3)<br />
4) (x + 1 ) (2x + 3) + 2 (x + 3)<br />
5) 2 (x + 1) (x + 3) + 2 (x + 3)<br />
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3. 12 men can complete a piece of work in 4 days, while 15 women can complete the same work in 4 days.<br />
6 men start working on the job and after working for two days, all of them stop working.<br />
How many women should be put on the jobto complete the remaining work, if it is to be completed in 3 days?<br />
1) 15<br />
2) 22<br />
3) 18<br />
4) Data inadequate<br />
5) None of these<br />
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4. A shopkeeper sells milk which contains 5% water. What quantity of pure milk should be added to 2 liters of milk<br />
(containing 5% water) so that proportion of water becomes 4%?<br />
1) 100 ml<br />
2) 250 ml<br />
3) 400 ml<br />
4) 350 ml<br />
5) None of these<br />
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5. 'A' and 'B' started a business in partnership investing Rs 20000/- and Rs 15000/- respectively. After six months 'C' jointed them with Rs 20000/-. What will be B's share in the total profit of Rs 25000/- earned at the end of two years from the starting of the business?<br />
1) Rs 9000/-<br />
2) Rs 10000/-<br />
3) Rs 7500/-<br />
4) Rs 9500/-<br />
5) Rs None of these<br />
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Directions (Q.6-10): In each of the following questions, a number series is given. After the series, below it a number along with (a), (b), (c), (d) and (e) is given. You have to complete the series following the same sequence as that of the given series. Then answer the question that follows.<br />
<br />
6. 8 6 9 23 87 429<br />
6 (a) (b) (c) (d) (e)<br />
What will come in place of (c)?<br />
1) 21<br />
2) 11<br />
3) 19<br />
4) 17<br />
5) None of these<br />
<br />
7. 2 3 10 39 172 885<br />
1 (a) (b) (c) (d) (e)<br />
What will come in place of (b)?<br />
1) 11<br />
2) 7<br />
3) 9<br />
4) 8<br />
5) None of these<br />
<br />
8. 5 7 10 36 136 690<br />
2 (a) (b) (c) (d) (e)<br />
What will come in place of (e)?<br />
1) 310<br />
2) 330<br />
3) 110<br />
4) 64<br />
5) None of these<br />
<br />
9. 8 9 13 11.5 18 14<br />
12 (a) (b) (c) (d) (e)<br />
What will come in place of (d)?<br />
1) 13.5<br />
2) 19.5<br />
3) 22<br />
4) 18<br />
5) None of these<br />
<br />
10. 8 4 6 15 52.5 236.25<br />
4 (a) (b) (c) (d) (e)<br />
Which of the following will come in place of (d)?<br />
1) 36.25<br />
2) 33.25<br />
3) 26.75<br />
4) 32.75<br />
5) None of these<br />
<br />
Directions: In the following question, four of the five words are similar in meaning. Find out the word that is different.<br />
11.<br />
1) Haggard<br />
2) Careworn<br />
3) Gaunt<br />
4) Hazard<br />
5) Anxious<br />
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12. Arrange the letters of word AUCTION in such a way that the vowels always occur together. Find the number of ways.<br />
1) 576<br />
2) 48<br />
3) 144<br />
4) 30<br />
5) None of these<br />
<br />
13. 2 metres broad pathway is to be constructed around a rectangular plot. The area of the plot is 96 sq.m.<br />
The cost of construction is Rs 50 per sq. metre. Then find the total cost of construction .<br />
1) Rs 4,800<br />
2) Rs 4,000<br />
3) Rs 2400<br />
4) Rs Data inadequate<br />
5) None of these<br />
<br />
14.Mr. A lends 40% of a sum at 15% pa, 50% of the rest sum at 10% pa and the rest at 18% pa rate of interest.<br />
What would be the rate of interest if the interest is calculated on the whole sum?<br />
1) 13.4% pa<br />
2) 14.33% pa<br />
3) 14.4% pa<br />
4) 13.33% pa<br />
5) None of these<br />
<br />
15. A sum of Rs 5000/- amounts to Rs 6050/- in two years at compound interest. What is the rate of interest?<br />
1) 15% pa<br />
2) 13% pa<br />
3) 11% pa<br />
4) 21% pa<br />
5) None of these<br />
<br />
Directions (Q. 16-20): Three statements follow below the question asked. How many statement (s) would be required to answer the question from the options given below?<br />
<br />
16. By selling an article what is the profit percent gained?<br />
(A) 5% discount is given on list price.<br />
(B) If discount is not given 20% profit would be gained. `<br />
(C) The cost price of the article is Rs 5000/-<br />
1) Only A and B<br />
2) Only A and C<br />
3) Only B and C<br />
4) All A, B and C together<br />
5) None of these<br />
<br />
17. What is the present age of father?<br />
(A) Difference in ages of father and son is 24 years.<br />
(B) Present age of son is of present age of father.<br />
(C) After 6 years from now, the age of son will be of father's age.<br />
1) Only A and B<br />
2) Only B and C<br />
3) Only A and C<br />
4) All A, B and C are together required<br />
5) Any two of the statements are required to answer the question.<br />
<br />
18. What is the cost of fencing a rectangular plot?<br />
(A) Length of the plot is twice its breadth.<br />
(B) Area of the plot is 288 square metres.<br />
(C) Cost of fencing is Rs 4/- per metre.<br />
1) B and C only<br />
2) A and C only<br />
3) A and B only<br />
4) All the three statements A, B and C are required to answer the question<br />
5) Question cannot be answered even with all the three statements together<br />
<br />
19. What is the length of the train?<br />
(A) The train crosses a signal pole in 18 seconds.<br />
(B) Train crosses a 200 m platform in 30 seconds.<br />
(C) Speed of the train is 60 kmph.<br />
1) A and C only<br />
2) B and C only<br />
3) C and A or B only<br />
4) A or B only<br />
5) None of these<br />
<br />
20. What will be the compound interest earned on an amount of Rs 5000/- in two years?<br />
(A) The simple interest on the same amount at the same rate of interest in five years is Rs 2000/-<br />
(B) The compound interest and the simple interest earned in one year are the same.<br />
(C) The amount becomes more than double on compound interest in 10 years.<br />
1) A and B only<br />
2) A only<br />
3) B and C only<br />
4) A and C only<br />
5) None of these<br />
<br />
Directions (Q. 21-25): Below is given a passage followed by several possible inferences which can be drawn from the facts stated in the passage. You have to examine each inference separately in the context of the passage and decide upon its degree of truth or falsity. Mark answer<br />
1) if the inference is "definitely true", ie it properly follows from the statement of facts given.<br />
2) if the inference is "probably true" though not "definitely true" in the light of the facts given<br />
3) if the "data are inadequate", ie from the facts given you cannot say whether the inference is likely to be true or false.<br />
4) if the inference is "probably false" though not "definitely false" in the light of the facts given.<br />
5) if the inference is "definitely false", ie it cannot possibly be drawn from the facts given or it contradicts the given facts.<br />
<br />
Increase in import of crude oil has become a major problem for the country. Now, the Indian government is formulating a national policy to promote bio-fuels. A host of fiscal incentives are on the cards. The aim is to ensure sustainable production, conversion and application of bio-fuels. As per a proposal before the Cabinet by the ministry of new and renewable energy, a national bio-fuel development board will be set up. The board's mandate is to partly replace petrol and diesel for transport and other applications.<br />
The policy will lay emphasis on research and development (R&D) for production, processing and commercialisation of bio-fuels like ethanol and jatropha. To promote bio-fuel development the government is aiming at fiscal sops. The fiscal sops for the bio-fuel sector could include excise and sales tax/VAT exemption. There will be a plan of action to use waste and degraded land for cultivation of jatropha. In some states, large-scale jatropha cultivation has already begun. This will be expanded in scope by providing economy of scale.<br />
<br />
21. The efforts made by the government will reduce he increasing and worrisome onus of crude oil imports on the fisc through gradual limited replacement of petroleum products with bio-fuels<br />
<br />
22. Oil extracted from jatropha seed can be used as bio-diesel.<br />
<br />
23. Many developed countries extensively use ethanol-blended petro fuels in the auto sector.<br />
<br />
24. India's oil marketing companies have not shown interest in tapping the market for bio-fuels.<br />
<br />
25. India has inexhaustible resource of crude oil.<br />
<br />
ANSWERS : 1. (2) 2. (4) 3. (1) 4. (5) 5. (3) 6. (2) 7. (4) 8. (2) 9. (3) 10. (5) 11. (4) 12. (1) 13. (4) 14. (3) 15. (5) 16. (1) 17. (5)18. (4) 19. (5) 20. (2)<br />
21. (2) 22. (3) 23. (3) 24. (4) 25. (4)Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-84176101732519535582011-02-14T03:59:00.000-08:002011-02-14T04:02:06.587-08:00SSIS InterView QuestionsSSIS- Sql Server Integration Services<br /><br />1) What is the control flow<br />2) what is a data flow<br />3) how do you do error handling in SSIS<br />4) how do you do logging in ssis<br />5) how do you deploy ssis packages.<br />6) how do you schedule ssis packages to run on the fly<br />7) how do you run stored procedure and get data<br />8) A scenario: Want to insert a text file into database table, but during the upload want to change a column called as months - January, Feb, etc to a code, - 1,2,3.. .This code can be read from another database table called months. After the conversion of the data , upload the file. If there are any errors, write to error table. Then for all errors, read errors from database, create a file, and mail it to the supervisor.<br />How would you accomplish this task in SSIS?<br />9)what are variables and what is variable scope ?<br />Answers<br />For Q 1 and 2:<br />In SSIS a workflow is called a control-flow. A control-flow links together our modular data-flows as a series of operations in order to achieve a desired result.<br /><br />A control flow consists of one or more tasks and containers that execute when the package runs. To control order or define the conditions for running the next task or container in the package control flow, you use precedence constraints to connect the tasks and containers in a package. A subset of tasks and containers can also be grouped and run repeatedly as a unit within the package control flow.<br /><br />SQL Server 2005 Integration Services (SSIS) provides three different types of control flow elements: containers that provide structures in packages, tasks that provide functionality, and precedence constraints that connect the executables, containers, and tasks into an ordered control flow.<br /><br />A data flow consists of the sources and destinations that extract and load data, the transformations that modify and extend data, and the paths that link sources, transformations, and destinations. Before you can add a data flow to a package, the package control flow must include a Data Flow task. The Data Flow task is the executable within the SSIS package that creates, orders, and runs the data flow. A separate instance of the data flow engine is opened for each Data Flow task in a package.<br /><br />SQL Server 2005 Integration Services (SSIS) provides three different types of data flow components: sources, transformations, and destinations. Sources extract data from data stores such as tables and views in relational databases, files, and Analysis Services databases. Transformations modify, summarize, and clean data. Destinations load data into data stores or create in-memory datasets.<br />Q3:<br />When a data flow component applies a transformation to column data, extracts data from sources, or loads data into destinations, errors can occur. Errors frequently occur because of unexpected data values.<br /><br />For example, a data conversion fails because a column contains a string instead of a number, an insertion into a database column fails because the data is a date and the column has a numeric data type, or an expression fails to evaluate because a column value is zero, resulting in a mathematical operation that is not valid.<br /><br />Errors typically fall into one the following categories:<br /><br />-Data conversion errors, which occur if a conversion results in loss of significant digits, the loss of insignificant digits, and the truncation of strings. Data conversion errors also occur if the requested conversion is not supported.<br />-Expression evaluation errors, which occur if expressions that are evaluated at run time perform invalid operations or become syntactically incorrect because of missing or incorrect data values.<br />-Lookup errors, which occur if a lookup operation fails to locate a match in the lookup table.<br /><br />Many data flow components support error outputs, which let you control how the component handles row-level errors in both incoming and outgoing data. You specify how the component behaves when truncation or an error occurs by setting options on individual columns in the input or output.<br /><br />For example, you can specify that the component should fail if customer name data is truncated, but ignore errors on another column that contains less important data.<br /><br />Q 4:<br />SSIS includes logging features that write log entries when run-time events occur and can also write custom messages.<br /><br />Integration Services supports a diverse set of log providers, and gives you the ability to create custom log providers. The Integration Services log providers can write log entries to text files, SQL Server Profiler, SQL Server, Windows Event Log, or XML files.<br /><br />Logs are associated with packages and are configured at the package level. Each task or container in a package can log information to any package log. The tasks and containers in a package can be enabled for logging even if the package itself is not.<br /><br />To customize the logging of an event or custom message, Integration Services provides a schema of commonly logged information to include in log entries. The Integration Services log schema defines the information that you can log. You can select elements from the log schema for each log entry.<br /><br />To enable logging in a package<br />1. In Business Intelligence Development Studio, open the Integration Services project that contains the package you want.<br />2. On the SSIS menu, click Logging.<br />3. Select a log provider in the Provider type list, and then click Add.<br />Q 5 :<br /><br />SQL Server 2005 Integration Services (SSIS) makes it simple to deploy packages to any computer.<br />There are two steps in the package deployment process:<br />-The first step is to build the Integration Services project to create a package deployment utility.<br />-The second step is to copy the deployment folder that was created when you built the Integration Services project to the target computer, and then run the Package Installation Wizard to install the packages.<br />Q 9 :<br /><br />Variables store values that a SSIS package and its containers, tasks, and event handlers can use at run time. The scripts in the Script task and the Script component can also use variables. The precedence constraints that sequence tasks and containers into a workflow can use variables when their constraint definitions include expressions.<br /><br />Integration Services supports two types of variables: user-defined variables and system variables. User-defined variables are defined by package developers, and system variables are defined by Integration Services. You can create as many user-defined variables as a package requires, but you cannot create additional system variables.<br /><br />Scope :<br /><br />A variable is created within the scope of a package or within the scope of a container, task, or event handler in the package. Because the package container is at the top of the container hierarchy, variables with package scope function like global variables and can be used by all containers in the package. Similarly, variables defined within the scope of a container such as a For Loop container can be used by all tasks or containers within the For Loop container.<br /><br /><br />Question 1 - True or False - Using a checkpoint file in SSIS is just like issuing the CHECKPOINT command against the relational engine. It commits all of the data to the database.<br />False. SSIS provides a Checkpoint capability which allows a package to restart at the point of failure.<br /><br />Question 2 - Can you explain the what the Import\Export tool does and the basic steps in the wizard?<br />The Import\Export tool is accessible via BIDS or executing the dtswizard command.<br />The tool identifies a data source and a destination to move data either within 1 database, between instances or even from a database to a file (or vice versa).<br /><br /><br />Question 3 - What are the command line tools to execute SQL Server Integration Services packages?<br />DTSEXECUI - When this command line tool is run a user interface is loaded in order to configure each of the applicable parameters to execute an SSIS package.<br />DTEXEC - This is a pure command line tool where all of the needed switches must be passed into the command for successful execution of the SSIS package.<br /><br /><br />Question 4 - Can you explain the SQL Server Integration Services functionality in Management Studio?<br />You have the ability to do the following:<br />Login to the SQL Server Integration Services instance<br />View the SSIS log<br />View the packages that are currently running on that instance<br />Browse the packages stored in MSDB or the file system<br />Import or export packages<br />Delete packages<br />Run packages<br /><br />Question 5 - Can you name some of the core SSIS components in the Business Intelligence Development Studio you work with on a regular basis when building an SSIS package?<br />Connection Managers<br />Control Flow<br />Data Flow<br />Event Handlers<br />Variables window<br />Toolbox window<br />Output window<br />Logging<br />Package Configurations<br /><br />Question Difficulty = Moderate<br /><br />Question 1 - True or False: SSIS has a default means to log all records updated, deleted or inserted on a per table basis.<br />False, but a custom solution can be built to meet these needs.<br /><br />Question 2 - What is a breakpoint in SSIS? How is it setup? How do you disable it?<br />A breakpoint is a stopping point in the code. The breakpoint can give the Developer\DBA an opportunity to review the status of the data, variables and the overall status of the SSIS package.<br />10 unique conditions exist for each breakpoint.<br />Breakpoints are setup in BIDS. In BIDS, navigate to the control flow interface. Right click on the object where you want to set the breakpoint and select the 'Edit Breakpoints...' option.<br /><br /><br />Question 3 - Can you name 5 or more of the native SSIS connection managers?<br />OLEDB connection - Used to connect to any data source requiring an OLEDB connection (i.e., SQL Server 2000)<br />Flat file connection - Used to make a connection to a single file in the File System. Required for reading information from a File System flat file<br />ADO.Net connection - Uses the .Net Provider to make a connection to SQL Server 2005 or other connection exposed through managed code (like C#) in a custom task<br />Analysis Services connection - Used to make a connection to an Analysis Services database or project. Required for the Analysis Services DDL Task and Analysis Services Processing Task<br />File connection - Used to reference a file or folder. The options are to either use or create a file or folder<br />Excel<br />FTP<br />HTTP<br />MSMQ<br />SMO<br />SMTP<br />SQLMobile<br />WMI<br /><br /><br />Question 4 - How do you eliminate quotes from being uploaded from a flat file to SQL Server?<br />In the SSIS package on the Flat File Connection Manager Editor, enter quotes into the Text qualifier field then preview the data to ensure the quotes are not included.<br />Additional information: How to strip out double quotes from an import file in SQL Server Integration Services<br />Question 5 - Can you name 5 or more of the main SSIS tool box widgets and their functionality?<br />For Loop Container<br />Foreach Loop Container<br />Sequence Container<br />ActiveX Script Task<br />Analysis Services Execute DDL Task<br />Analysis Services Processing Task<br />Bulk Insert Task<br />Data Flow Task<br />Data Mining Query Task<br />Execute DTS 2000 Package Task<br />Execute Package Task<br />Execute Process Task<br />Execute SQL Task<br />etc.<br /><br />Question Difficulty = Difficult<br /><br />Question 1 - Can you explain one approach to deploy an SSIS package?<br />One option is to build a deployment manifest file in BIDS, then copy the directory to the applicable SQL Server then work through the steps of the package installation wizard<br />A second option is using the dtutil utility to copy, paste, rename, delete an SSIS Package<br />A third option is to login to SQL Server Integration Services via SQL Server Management Studio then navigate to the 'Stored Packages' folder then right click on the one of the children folders or an SSIS package to access the 'Import Packages...' or 'Export Packages...'option.<br />A fourth option in BIDS is to navigate to File | Save Copy of Package and complete the interface.<br /><br /><br /><br />Question 2 - Can you explain how to setup a checkpoint file in SSIS?<br />The following items need to be configured on the properties tab for SSIS package:<br />CheckpointFileName - Specify the full path to the Checkpoint file that the package uses to save the value of package variables and log completed tasks. Rather than using a hard-coded path as shown above, it's a good idea to use an expression that concatenates a path defined in a package variable and the package name.<br />CheckpointUsage - Determines if/how checkpoints are used. Choose from these options: Never (default), IfExists, or Always. Never indicates that you are not using Checkpoints. IfExists is the typical setting and implements the restart at the point of failure behavior. If a Checkpoint file is found it is used to restore package variable values and restart at the point of failure. If a Checkpoint file is not found the package starts execution with the first task. The Always choice raises an error if the Checkpoint file does not exist.<br />SaveCheckpoints - Choose from these options: True or False (default). You must select True to implement the Checkpoint behavior.<br /><br />Question 3 - Can you explain different options for dynamic configurations in SSIS?<br />Use an XML file<br />Use custom variables<br />Use a database per environment with the variables<br />Use a centralized database with all variables<br /><br />Question 4 - How do you upgrade an SSIS Package?<br />Depending on the complexity of the package, one or two techniques are typically used:<br />Recode the package based on the functionality in SQL Server DTS<br />Use the Migrate DTS 2000 Package wizard in BIDS then recode any portion of the package that is not accurate<br /><br /><br />Question 5 - Can you name five of the Perfmon counters for SSIS and the value they provide?<br />SQLServer:SSIS Service<br />SSIS Package Instances - Total number of simultaneous SSIS Packages running<br />SQLServer:SSIS Pipeline<br />BLOB bytes read - Total bytes read from binary large objects during the monitoring period.<br />BLOB bytes written - Total bytes written to binary large objects during the monitoring period.<br />BLOB files in use - Number of binary large objects files used during the data flow task during the monitoring period.<br />Buffer memory - The amount of physical or virtual memory used by the data flow task during the monitoring period.<br />Buffers in use - The number of buffers in use during the data flow task during the monitoring period.<br />Buffers spooled - The number of buffers written to disk during the data flow task during the monitoring period.<br />Flat buffer memory - The total number of blocks of memory in use by the data flow task during the monitoring period.<br />Flat buffers in use - The number of blocks of memory in use by the data flow task at a point in time.<br />Private buffer memory - The total amount of physical or virtual memory used by data transformation tasks in the data flow engine during the monitoring period.<br />Private buffers in use - The number of blocks of memory in use by the transformations in the data flow task at a point in time.<br />Rows read - Total number of input rows in use by the data flow task at a point in time.<br />Rows written - Total number of output rows in use by the data flow task at a point in time.Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-49949577486843794532010-10-29T05:41:00.001-07:002010-10-29T05:47:13.162-07:00Dot Net Interview Questions<meta equiv="Content-Type" content="text/html; charset=utf-8"><meta name="ProgId" content="Word.Document"><meta name="Generator" content="Microsoft Word 12"><meta name="Originator" content="Microsoft Word 12"><link rel="File-List" href="file:///C:%5CDOCUME%7E1%5Celvinsir%5CLOCALS%7E1%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_filelist.xml"><link rel="themeData" href="file:///C:%5CDOCUME%7E1%5Celvinsir%5CLOCALS%7E1%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_themedata.thmx"><link rel="colorSchemeMapping" 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mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} </style> <![endif]--> <p style="margin-bottom: 14pt;"><strong><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">Question:-What do you mean by Share Point Portal ?</span></strong><b><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">
<br /><strong><span style="font-family: "Verdana","sans-serif";">Answer:</span></strong></span></b><span style="font-size: 9pt; font-family: "Verdana","sans-serif";"> <span class="style61">Here I have taken information regarding Share Point Portal Server 2003 provides mainly access to the crucial business information and applications. With the help of Share Point Server we can server information between Public Folders, Data Bases, File Servers and the websites that are based on Windows server 2003. This Share Point Portal is integrated with MSAccess and Windows servers, So we can get a Wide range of document management functionality. We can also create a full featured portal with readymade navigation and structure.<o:p></o:p></span></span></p> <p class="MsoNormal"><strong><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">Question:-What is cross page posting in ASP.NET2.0 ?</span></strong><b><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">
<br /><strong><span style="font-family: "Verdana","sans-serif";">Answer:</span></strong><span class="style111"> </span></span></b><span class="style61"><span style="font-size: 9pt;">When we have to post data from one page to another in application we used server.transfer method but in this the URL remains the same but in cross page posting there is little different there is normal post back is done but in target page we can access values of server control in the source page.This is quite simple we have to only set the PostBackUrl property of Button,LinkButton or imagebutton which specifies the target page. In target page we can access the PreviousPage property. and we have to use the @PreviousPageType directive. We can access control of PreviousPage by using the findcontrol method. When we set the PostBackURL property ASP.NET framework bind the HTML and Javascript function automatically.<o:p></o:p></span></span></p> <p><span class="style111"><span style="font-size: 9pt;">Question: How to start Outlook,NotePad file in AsP.NET with code ?</span></span><b><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">
<br /><span class="style111">Answer:</span></span></b><span class="style61"><span style="font-size: 9pt;"> Here is the syntax to open outlook or notepad file in ASP.NET VB.NET Process.Start("Notepad.exe") Process.Start("msimn.exe"); C#.NET System.Diagnostics.Process.Start("msimn.exe"); System.Diagnostics.Process.Start("Notepad.exe"); </span></span><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">
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<br /><span class="style111">Question: What is the purpose of IIS ?</span><b>
<br /><span class="style111">Answer:</span></b><span class="style61"> We can call IIS(Internet Information Services) a powerful Web server that helps us creating highly reliable, scalable and manageable infrastructure for Web application which runs on Windows Server 2003. IIS helps development center and increase Web site and application availability while lowering system administration costs. It also runs on Windows NT/2000 platforms and also for above versions. With IIS, Microsoft includes a set of programs for building and administering Web sites, a search engine, and support for writing Web-based applications that access database. IIS also called http server since it process the http request and gets http response.</span>
<br />
<br /><span class="style111">Question: What is main difference between GridLayout and FormLayout ?</span><b>
<br /><span class="style111">Answer:</span></b><span class="style61"> GridLayout helps in providing absolute positioning of every control placed on the page. It is easier to develop page with absolute positioning because control can be placed any where according to our requirement. But FormLayout is little different only experience Web Developer used this one reason is it is helpful for wider range browser. If there is absolute positioning we can notice that there are number of DIV tags. But in FormLayout whole work are done through the tables.</span>
<br />
<br /><span class="style111">Question: How Visual SourceSafe helps Us ?</span><b>
<br /><span class="style111">Answer:</span></b><span class="style61"> One of the powerful tool provided by Microsoft to keep up-to-date of files system its keeps records of file history once we add files to source safe it can be add to database and the changes ads by different user to this files are maintained in database from that we can get the older version of files to. This also helps in sharing,merging of files.</span>
<br />
<br /><span class="style111">Question:-Can you define what is SharePoint and some overview about this ?</span><b>
<br /><span class="style111">Answer: </span></b><span class="style61">SharePoint helps workers for creating powerful personalized interfaces only by dragging and drop pre-defined Web Part Components. And these Web Parts components also helps non programmers to get information which care and customize the appearance of Web pages. To under stand it we take an example one Web Part might display a user's information another might create a graph showing current employee status and a third might show a list of Employees Salary. This is also possible that each functions has a link to a video or audio presentation. So now Developers are unable to create these Web Part components and make them available to SharePoint users.</span>
<br /><b>
<br /><span class="style111">Question:-What is different between WebUserControl and in WebCustomControl ?</span></b>
<br /><span class="style111">Answer:</span> <span class="style61"><b>Web user controls :-</b> Web User Control is Easier to create and another thing is that its support is limited for users who use a visual design tool one good thing is that its contains static layout one more thing a separate copy is required for each application. </span>
<br /><span class="style61"><b>Web custom controls:-</b>Web Custom Control is typical to create and good for dynamic layout and another thing is it have full tool support for user and a single copy of control is required because it is placed in Global Assembly cache. </span>
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<br /><span class="style111">Question:-What is Sandbox in SQL server and explain permission level in Sql Server ?</span>
<br /><span class="style111">Answer:</span> Sandbox is place where we run trused program or script which is created from the third party. There are three type of Sandbox where user code run.
<br /><strong><span style="font-family: "Verdana","sans-serif";">Safe Access Sandbox</span></strong>:-Here we can only create stored procedure,triggers,functions,datatypes etc.But we doesnot have acess memory ,disk etc.
<br /><strong><span style="font-family: "Verdana","sans-serif";">External Access Sandbox</span></strong>:-We cn access File systems outside the box. We can not play with threading,memory allocation etc.
<br /><strong><span style="font-family: "Verdana","sans-serif";">Unsafe Access Sandbox</span></strong>:-Here we can write unreliable and unsafe code.<o:p></o:p></span></p> <p><span class="style111"><span style="font-size: 9pt;">Question:-How many types of cookies are there in .NET ?</span></span><b><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">
<br /><span class="style111">Answer: </span></span></b><span class="style61"><span style="font-size: 9pt;">Two type of cookeies.</span></span><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">
<br /><span class="style61">a) single valued eg request.cookies(”UserName”).value=”dotnetquestion”</span>
<br /><span class="style61">b)Multivalued cookies. These are used in the way collections are used example</span>
<br /><span class="style61">request.cookies(”CookiName”)(”UserName”)=”dotnetquestionMahesh”</span>
<br /><span class="style61">request.cookies(”CookiName”)(”UserID”)=”interview″</span>
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<br /><span class="style111">Question: When we get Error 'HTTP 502 Proxy Error' ?</span><b>
<br /><span class="style111">Answer:</span></b> <span class="style61">We get this error when we execute ASP.NET Web pages in Visual Web Developer Web server, because the URL randomly select port number and proxy servers did not recognize the URL and return this error. To resolve this problem we have to change settings in Internet Explorer to bypass the proxy server for local addresses, so that the request is not sent to the proxy. </span>
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<br /><span class="style111">Question:-What do you mean by three-tier architecture?</span>
<br /><span class="style111">Answer:</span><span class="style61"> The three-tier architecture was comes into existence to improve management of code and contents and to improve the performance of the web based applications. There are mainly three layers in three-tier architecture. the are define as follows <o:p></o:p></span></span></p> <p style="margin: 0in 0in 0.0001pt;"><span class="style61"><span style="font-size: 9pt;">(1)Presentation </span></span><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">
<br /><span class="style61">(2)Business Logic <o:p></o:p></span></span></p> <p style="margin: 0in 0in 0.0001pt;"><span class="style61"><span style="font-size: 9pt;">(3)Database </span></span><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">
<br /> <!--[if !supportLineBreakNewLine]-->
<br /> <!--[endif]--><o:p></o:p></span></p> <p style="margin: 0in 0in 0.0001pt;"><span class="style61"><span style="font-size: 9pt;">(1)<b>First layer</b> Presentation contains mainly the interface code, and this is shown to user. This code could contain any technology that can be used on the client side like HTML, JavaScript or VBScript etc.</span></span><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">
<br /> <!--[if !supportLineBreakNewLine]-->
<br /> <!--[endif]--><o:p></o:p></span></p> <p style="margin: 0in 0in 0.0001pt;"><span class="style61"><span style="font-size: 9pt;">(2)<b>Second layer</b> is Business Logic which contains all the code of the server-side .This layer have code to interact with database and to query, manipulate, pass data to user interface and handle any input from the UI as well. </span></span><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">
<br /> <!--[if !supportLineBreakNewLine]-->
<br /> <!--[endif]--><o:p></o:p></span></p> <p class="MsoNormal"><span class="style61"><span style="font-size: 9pt;">(3)<b>Third layer</b> Data represents the data store like MS Access, SQL Server, an XML file, an Excel file or even a text file containing data also some additional database are also added to that layers.</span></span><span style="font-size: 9pt; font-family: "Verdana","sans-serif";">
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<br /><span class="style111">Question: What is Finalizer in .NET define Dispose and Finalize?</span><b>
<br /><span class="style111">Answer:</span></b> <span class="style61">We can say that Finalizer are the methods that's helps in cleanp the code that is executed before object is garbage collected .The process is called finalization . There are two methods of finalizer Dispose and Finalize .There is little diffrenet between two of this method .</span>
<br />When we call <span class="style61">Dispose method is realse all the resources hold by an object as well as all the resorces hold by the parent object.When we call Dispose method it clean managed as well as unmanaged resources.</span>
<br /><span class="style61">Finalize methd also cleans resources but finalize call dispose clears only the unmanged resources because in finalization the garbase collecter clears all the object hold by managed code so finalization fails to prevent thos one of methd is used that is: GC.SuppressFinalize.</span>
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<br /><span class="style111">Question: What is late binding ?</span><b>
<br /><span class="style111">Answer:</span></b> <span class="style61">When code interacts with an object dynamically at runtime .because our code literally doesnot care what type of object it is interacting and with the methods thats are supported by object and with the methods thats are supported by object .The type of object is not known by the IDE or compiler ,no Intellisense nor compile-time syntax checking is possible but we get unprecedented flexibilty in exchange.if we enable strict type checking by using option strict on at the top of our code modules ,then IDE and compiler will enforce early binding behaviour .By default Late binding is done. </span>
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<br /><strong><span style="font-family: "Verdana","sans-serif";">Question:-Does .NET CLR and SQL SERVER run in different process?</span></strong><b>
<br /><strong><span style="font-family: "Verdana","sans-serif";">Answer:</span></strong><span class="style111"> </span></b><span class="style61">Dot Net CLR and all .net realtes application and Sql Server run in same process or we can say that that on the same address because there is no issue of speed because if these two process are run in different process then there may be a speed issue created one process goes fast and other slow may create the problem.</span>
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<br /><span class="style111">Question: The IHttpHandler and IHttpHandlerFactory interfaces ?</span><b>
<br /><span class="style111">Answer:</span></b> <span class="style61">The IHttpHandler interface is implemented by all the handlers. The interface consists of one property called IsReusable. The IsReusable property gets a value indicating whether another request can use the IHttpHandler instance. The method ProcessRequest() allows you to process the current request. This is the core place where all your code goes. This method receives a parameter of type HttpContext using which you can access the intrinsic objects such as Request and Response. The IHttpHandlerFactory interface consists of two methods - GetHandler and ReleaseHandler. The GetHandler() method instantiates the required HTTP handler based on some condition and returns it back to ASP.NET. The ReleaseHandler() method allows the factory to reuse an existing handler.</span>
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<br /><span class="style111">Question: what is Viewstate? </span><b>
<br /><strong><span style="font-family: "Verdana","sans-serif";">Answer:</span></strong></b><span class="style61">View state is used by the ASP.NET page framework to automatically save the values of the page and of each control just prior to rendering to the page. When the page is posted, one of the first tasks performed by page processing is to restore view state.</span>
<br /><span class="style61">State management is the process by which you maintain state and page information over multiple requests for the same or different pages. <o:p></o:p></span></span></p> <p class="MsoNormal"><span class="style61"><span style="font-size: 9pt;"><o:p> </o:p></span></span></p> Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-70024775844129771232010-10-27T02:53:00.001-07:002010-10-27T02:54:18.362-07:00The future of SCTP<p>SCTP is a relatively new protocol, considering that it became an RFC in October 2000. Since then, it has found its way into all major operating systems, including GNU/Linux, BSD, and Solaris. It's also available for the Microsoft® Windows® operating systems as a third-party commercial package.</p> <p>Along with availability, applications will begin to use SCTP as their primary transport. Traditional applications such as FTP and HTTP have been built on the features of SCTP. Other protocols are using SCTP, such as the Session Initiation Protocol (SIP) and the Common Channel Signaling System No. 7 (SS7). Commercially, you can find SCTP in Cisco's IOS.</p> <p>With the inclusion of SCTP into the 2.6 Linux kernel, it's now possible to build and deploy highly available and reliable networked applications. As an IP-based protocol, SCTP is a seamless replacement for TCP and UDP but also extends new services, such as multi-homing, multi-streaming, and increased security. Now that you've seen some of the high-level features of SCTP, explore its other capabilities. The Linux Kernel SCTP project (lksctp) provides API extensions and documentation that will help you on your way.</p>Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-76643938449095282932010-10-27T02:50:00.000-07:002010-10-27T02:52:49.433-07:00Better networking with SCTP<em style="font-weight: bold;">The Stream Control Transmission Protocol combines advantages from both TCP and UDP<br /><br /></em>The Stream Control Transmission Protocol (SCTP) is a reliable transport protocol that provides stable, ordered delivery of data between two endpoints (much like TCP) and also preserves data message boundaries (like UDP). However, unlike TCP and UDP, SCTP offers such advantages as multi-homing and multi-streaming capabilities, both of which increase availability. In this article, get to know the key features of SCTP in the Linux® 2.6 kernel and take a look at the server and client source code that shows the protocol's ability to deliver multi-streaming.<br /><br /><p>SCTP is a reliable, general-purpose transport layer protocol for use on IP networks. While the protocol was originally designed for telephony signaling (under the RFC 2960), SCTP provided an added bonus -- it solved some of the limitations of TCP while borrowing beneficial features of UDP. SCTP provides features for high availability, increased reliability, and improved security for socket initiation. (Figure 1 shows the layered architecture of the IP stack.)</p> <br /><a name="N1006A"><b>Figure 1. Layered architecture of the IP stack</b></a><br /><img alt="Layered architecture of the IP stack" src="http://www.ibm.com/developerworks/linux/library/l-sctp/figure1.gif" width="284" height="151" /><br /> <p> This article introduces the concept of SCTP in the Linux 2.6 kernel, highlights some of the advanced features (such as multi-homing and -streaming), and provides server and client source code snippets (with a URL to more code) to demonstrate the protocol's ability to deliver multi-streaming. </p> <p> Let's start with an overview of the IP stack. </p> <p><a name="N1007D"><span class="atitle">The IP stack</span></a></p> <p>The Internet protocol suite is split into several layers; each layer provides specific functionality as shown in Figure 1. </p> <p> Starting from the bottom: </p> <ul><li> The <i>link layer</i> provides the physical interface to the communication medium (such as an Ethernet device). </li><li> The <i>network layer</i> manages the movement of packets in a network, specifically making sure packets get to their destination (also called <i>routing</i>). </li><li> The <i>transport layer</i> regulates the flow of packets between two hosts for the application layer. It also presents the application endpoint for communication, known as a <i>port.</i> </li><li> Finally, the <i>application layer</i> provides meaning to the data transported through the socket. This data could consist of e-mail messages using the Simple Mail Transport Protocol (SMTP) or Web pages rendered through the Hypertext Transport Protocol (HTTP). </li></ul> <p>All application layer protocols use the sockets layer as their interface to the transport layer protocol. The Sockets API was developed at UC Berkeley within the BSD UNIX® operating system. </p> <p> Now for a quick refresher on traditional transport layer protocols before we dive into the workings of SCTP. </p> <p><a name="N100B4"><span class="atitle">The transport layer protocols</span></a></p> <p>The two most popular transport layer protocols are the transmission control protocol (TCP) and the user datagram protocol (UDP): </p> <ul><li> TCP is a reliable protocol that guarantees sequenced, ordered delivery of data and manages congestion within a network.</li><li> UDP is a message-oriented protocol that neither guarantees ordering of delivery nor manages congestion.</li></ul> <p> However, UDP is a fast protocol that preserves the boundaries of the messages it transports.</p> <p>This article presents another option: SCTP. It provides the reliable, ordered delivery of data like TCP but operates in the message-oriented fashion like UDP, preserving message boundaries. SCTP also provides several advanced features:</p> <ul><li>Multi-homing</li><li>Multi-streaming</li><li>Initiation protection</li><li>Message framing</li><li>Configurable unordered delivery</li><li>Graceful shutdown</li></ul> <p><a name="N100E3"><span class="atitle">Key features of SCTP</span></a></p> <p>The two most important enhancements in SCTP over traditional transport layer protocols are the end-host multi-homing and multi-streaming capabilities.</p> <p><a name="N100EE"><span class="smalltitle">Multi-homing</span></a></p> <p><i>Multi-homing</i> provides applications with higher availability than those that use TCP. A multi-homed host is one that has more than one network interface and therefore more than one IP address for which it can be addressed. In TCP, a <i>connection</i> refers to a channel between two endpoints (in this case, a socket between the interfaces of two hosts). SCTP introduces the concept of an <i>association</i> that exists between two hosts but can potentially collaborate with multiple interfaces at each host.</p> <p>Figure 2 illustrates the difference between a TCP connection and an SCTP association. </p> <br /><a name="N10104"><b>Figure 2. TCP connection vs. an SCTP association</b></a><br /><img alt="TCP connection vs. an SCTP association" src="http://www.ibm.com/developerworks/linux/library/l-sctp/figure2.gif" width="485" height="325" /><br /> <p> At the top is a TCP connection. Each host includes a single network interface; a connection is created between a single interface on each of the client and server. Upon establishment, the connection is bound to each interface. </p> <p>At the bottom of the figure, you can see an architecture that includes two network interfaces per host. Two paths are provided through the independent networks, one from interface C0 to S0 and another from C1 to S1. In SCTP, these two paths would be collected into an association. </p> <p>SCTP monitors the paths of the association using a built-in heartbeat; upon detecting a path failure, the protocol sends traffic over the alternate path. It's not even necessary for the applications to know that a failover recovery occurred. </p> <p>Failover can also be used to maintain network application connectivity. For example, consider a laptop that includes a wireless 802.11 interface and an Ethernet interface. When the laptop is in its docking station, the higher-speed Ethernet interface would be preferred (in SCTP, called the <i>primary address</i>); but upon loss of this connection (removal from the docking station), connections would be failed over to the wireless interface. Upon return to the docking station, the Ethernet connection would be detected and communication resumed over this interface. This is a powerful mechanism for providing high availability and increased reliability. </p> <p><a name="N10120"><span class="smalltitle">Multi-streaming</span></a></p> <p>In some ways, an SCTP association is like a TCP connection except that SCTP supports multiple streams within an association. All the streams within an association are independent but related to the association (see Figure 3). </p> <br /><a name="N1012B"><b>Figure 3. Relationship of an SCTP association to streams</b></a><br /><img alt="Relationship of an SCTP association to streams" src="http://www.ibm.com/developerworks/linux/library/l-sctp/figure3.gif" width="463" height="164" /><br /> <p>Each stream is given a stream number that is encoded inside SCTP packets flowing through the association. Multi-streaming is important because a blocked stream (for example, one awaiting re-transmission resulting from the loss of a packet) does not affect the other streams in an association. This problem is commonly referred to as <i>head-of-line blocking</i>. TCP is prone to such blocking.</p> <p> How can multiple streams provide better responsiveness in transporting data? For example, the HTTP protocol shares control and data over the same socket. A Web client requests a file from a server, and the server sends the file back over the same connection. A multi-streamed HTTP server would provide better interactivity because multiple requests could be serviced on independent streams within the association. This functionality would parallelize the responses, and while not potentially faster, would simultaneously load the HTML and graphics images, providing the perception of better responsiveness. </p> <p>Multi-streaming is an important feature of SCTP, especially when you consider some of the control and data issues in protocol design. In TCP, control and data typically share the same connection, which can be problematic because control packets can be delayed behind data packets. If control and data were split into independent streams, control data could be dealt with in a more timely manner, resulting in better utilization of available resources.</p> <p><a name="N10144"><span class="smalltitle">Initiation protection</span></a></p> <p>Initiating a new connection in TCP and SCTP occurs with a packet handshake. In TCP, it's a called a <i>three-way handshake.</i> The client sends a <code>SYN</code> packet (short for <i>Synchronize</i>) for which the server responds with a <code>SYN-ACK</code> packet (<i>Synchronize-Acknowledge</i>). Finally, the client confirms receipt with an <code>ACK</code> packet (see Figure 4). </p> <br /><a name="N10164"><b>Figure 4. The packet exchanges for the TCP and STCP handshake</b></a><br /><img style="width: 481px; height: 227px;" alt="The packet exchanges for the TCP and SCTP handshake" src="http://www.ibm.com/developerworks/linux/library/l-sctp/figure4.gif" /><br /> <p> The problem that can occur with TCP is when a rogue client forges an IP packet with a bogus source address, then floods a server with TCP <code>SYN</code> packets. The server allocates resources for the connections upon receipt of the <code>SYN</code>, then under a flood of <code>SYN</code> packets, eventually runs out and is unable to service new requests. This is called a <i>Denial of Service</i> (DoS) attack.</p> <p>SCTP protects against this type of attack through a four-way handshake and the introduction of a cookie. In SCTP, a client initiates a connection with an <code>INIT</code> packet. The server responds with an <code>INIT-ACK</code>, which includes the cookie (a unique context identifying this proposed connection). The client then responds with a <code>COOKIE-ECHO</code>, which contains the cookie sent by the server. At this point, the server allocates the resource for the connection and acknowledges this by sending a <code>COOKIE-ACK</code> to the client.</p> <p>To solve the problem of delayed data movement with the four-way handshake, SCTP permits data to be included in the <code>COOKIE-ECHO</code> and <code>COOKIE-ACK</code> packets.</p> <p><a name="N101A1"><span class="smalltitle">Message framing</span></a></p> <p>With message framing, the boundaries in which messages are communicated through a socket are preserved; this means that if a client sends 100 bytes to a server followed by 50 bytes, the server will read 100 bytes and 50 bytes, respectively, for two reads. UDP also operates in this way, which makes it advantageous for message-oriented protocols. </p> <p>In contrast, TCP operates in a byte-stream fashion. Without framing, a peer may receive more or less than was sent (splitting up a write or aggregating multiple writes into a single read). This behavior requires that message-oriented protocols operating over TCP provide data-buffer and message framing within their application layer (a potentially complex task).</p> <p>SCTP provides for message framing in data transfer. When a peer performs a write on a socket, it is guaranteed that this same-sized chunk of data will be read at the peer endpoint (see Figure 5). </p> <br /><a name="N101B3"><b>Figure 5. Message framing in UDP/SCTP vs. a byte-stream-oriented protocol</b></a><br /><img style="width: 346px; height: 164px;" alt="Message framing in UDP/SCTP vs. a byte-stream-oriented protocol" src="http://www.ibm.com/developerworks/linux/library/l-sctp/figure5.gif" /><br /> <p> For stream-oriented data, such as audio or video data, lack of framing is acceptable.</p> <p><a name="N101C3"><span class="smalltitle">Configurable unordered delivery</span></a></p> <p>Messages in SCTP are transferred reliably but not necessarily in the desired order. TCP guarantees that data is delivered in order (which is a good thing, considering TCP is a stream protocol). UDP guarantees no ordering. But, you can also configure streams within SCTP to accept unordered messages if desired.</p> <p>This feature can be useful in message-oriented protocols in which requests are independent and ordering is not important. Further, you can configure unordered delivery on a stream-by-stream basis within an association.</p> <p><a name="N101CF"><span class="smalltitle">Graceful shutdown</span></a></p> <p>TCP and SCTP are connection-based protocols, while UDP is a connection-less protocol. Both TCP and SCTP require connection setup and teardown between peers. What's different about socket shutdown in SCTP is the removal of TCP's <i>half-close</i>.</p> <p>Figure 6 shows the shutdown sequences for TCP and SCTP. </p> <br /><a name="N101E0"><b>Figure 6. TCP and SCTP connection termination sequences</b></a><br /><img style="width: 362px; height: 171px;" alt="TCP and SCTP connection termination sequences" src="http://www.ibm.com/developerworks/linux/library/l-sctp/figure6.gif" /><br /> <p> In TCP, it's possible for a peer to close its end of a socket (resulting in a <code>FIN</code> packet being sent) but then to continue to receive data. The <code>FIN</code> indicates that no more data is to be sent by this endpoint, but until the peer closes its end of the socket, it may continue to transmit data. Applications rarely use this half-closed state, and therefore the SCTP designers opted to remove it and replace it with a cleaner termination sequence. When a peer closes its socket (resulting in the issuance of a <code>SHUTDOWN</code> primitive), both endpoints are required to close, and no further data movement is permitted in either direction.</p> <p><a name="N101FC"><span class="atitle">Multi-streaming demo</span></a></p> <p>Now that you know the basic features of SCTP, let's look at a sample server and client that are written in the C programming language and demonstrate SCTP's multi-streaming feature.</p> <p>This example presents a server that implements a form of the daytime protocol. This traditional server emits the current time to a connected client, but for SCTP, I emit the local time on stream 0 and Greenwich Mean Time (GMT) on stream 1. This simple example allows me to demonstrate the APIs for stream communication. </p> <p>Figure 7 outlines the entire process and shows not only the flow of the application from a sockets API perspective but also the relationships from a client and server perspective.</p> <br /><a name="N1020F"><b>Figure 7. Sockets functions used in the multi-streaming daytime server and client</b></a><br /><img style="width: 400px; height: 499px;" alt="Sockets functions used in the multi-streaming daytime server and client" src="http://www.ibm.com/developerworks/linux/library/l-sctp/figure7.gif" /><br /> <p>These applications were developed on the GNU/Linux operating system with a 2.6.11 kernel and the Linux Kernel SCTP project (lksctp). The nonstandard sockets functions are provided in the lksctp tools package, which is available from SourceForge. See <a href="http://www.ibm.com/developerworks/linux/library/l-sctp/#resources">Resources</a> for links. </p> <p><a name="N10223"><span class="smalltitle">The daytime server</span></a></p> <p>The multi-stream daytime server is shown in Listing 1. All error checking is omitted in Listing 1 for better readability, but the <a href="http://www.ibm.com/developerworks/linux/library/l-sctp/#download">code you can download below</a> demonstrates error checking as well as other SCTP socket extensions.</p>Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-58750454400017988432010-10-27T02:45:00.000-07:002010-10-27T02:47:32.141-07:00Tracing a hacker<span name="intelliTxt" id="intelliTxt">Sometimes, it's just not enough to simply know that there's a Trojan or Virus onboard. Sometimes you need to know exactly <i>why</i> that file is onboard, how it got there - but most importantly, <b>who put it there</b>.<br /><br />By enumerating the attacker in the same way that they have enumerated the victim, you will be able to see the bigger picture and establish what you're up against. But how can you do this? Read on...<br /><br /><b>## Connections make the world go round ##</b><br /><br />The computer world, at any rate. Every single time you open up a website, send an email or upload your webpages into cyberspace, you are connecting to another machine in order to get the job done. This, of course, presents a major problem, because this simple act is what allows malicious users to target a machine in the first place.<br /><br /><b># How do these people find their victim?</b><br /><br />Well, first of all, they need to get hold of the victim's IP Address. Your IP (Internet Protocol) address reveals your point of entry to the Internet and can be used in many ways to cause your online activities many, many problems. It may not reveal you by name, but it may be uniquely identifiable and it represents your digital ID while you are online (especially so if you're on a fixed IP / DSL etc).<br /><br />With an IP address, a Hacker can find out all sorts of weird and wonderful things about their victim (as well as causing all kinds of other trouble, the biggest two being Portnukes/Trojans and the dreaded DoS ((Denial of Service)) attack). Some Hackers like to collect IP Addresses like badges, and like to go back to old targets, messing them around every so often. An IP address is incredibly easy to obtain - until recently, many realtime chat applications (such as MSN) were goldmines of information. Your IP Address is contained as part of the Header Code on all emails that you send and webpages that you visit can store all kinds of information about you. A common trick is for the Hacker to go into a Chatroom, paste his supposed website address all over the place, and when the unsuspecting victim visits, everything about your computer from the operating system to the screen resolution can be logged...and, of course, the all important IP address. In addition, a simple network-wide port scan will reveal vulnerable target machines, and a war-dialler will scan thousands of lines for exposed modems that the hacker can exploit.<br /><br />So now that you know some of the basic dangers, you're probably wondering how these people connect to a victim's machine?<br /><br /><b>## Virtual and Physical Ports ##</b><br /><br />Everything that you recieve over the Internet comes as a result of other machines connecting to your computer's ports. You have two types; Physical are the holes in the back of your machine, but the important ones are <i>Virtual</i>. These allow transfer of data between your computer and the outside world, some with allocated functions, some without, but knowing how these work is the first step to discovering who is attacking you; you simply MUST have a basic knowledge of this, or you won't get much further.<br /><br /><b># What the phrases TCP/UDP actually mean</b><br /><br />TCP/IP stands for Transmission Control Protocol and Internet Protocol, a TCP/IP packet is a block of data which is compressed, then a header is put on it and it is sent to another computer (UDP stands for User Datagram Protocol). This is how ALL internet transfers occur, by sending packets. The header in a packet contains the IP address of the one who originally sent you it. Now, your computer comes with an excellent (and free) tool that allows you to see anything that is connected (or is attempting to connect) to you, although bear in mind that it offers no blocking protection; it simply tells you what is going on, and that tool is <b>NETSTAT</b>.<br /><br /><b>## Netstat: Your first line of defence ##</b><br /><br />Netstat is a very fast and reliable method of seeing exactly who or what is connected (or connecting) to your computer. Open up DOS (Start/Programs/MS-DOS Prompt on most systems), and in the MSDOS Prompt, type:<br /><br /><b>netstat -a</b><br /><br />(make sure you include the space inbetween the "t" and the "a").<br /><br />If you're connected to the Internet when you do this, you should see something like:<br /><br /><!--QuoteBegin--></span><table align="center" border="0" cellpadding="3" cellspacing="1" width="95%"><tbody><tr><td><b>QUOTE</b> </td></tr><tr><td id="QUOTE"><!--QuoteEBegin-->Active Connections<br /><br />Proto Local Address Foreign Address State<br />TCP macintosh: 20034 modem-123.tun.dialup.co.uk: 50505 ESTABLISHED<br />TCP macintosh: 80 proxy.webcache.eng.sq: 30101 TIME_WAIT<br />TCP macintosh MACINTOSH: 0 LISTENING<br />TCP macintosh MACINTOSH: 0 LISTENING<br />TCP macintosh MACINTOSH: 0 LISTENING<!--QuoteEnd--></td></tr></tbody></table><div class="postcolor"><!--QuoteEEnd--><br /><br />Now, "Proto(col)" simply means what kind of data transmission is taking place (TCP or UDP), "Local address" is your computer (and the number next to it tells you what port you're connected on), "Foreign Address" is the machine that is connected to you (and what port they're using), and finally "State" is simply whether or not a connection is actually established, or whether the machine in question is waiting for a transmission, or timing out etc.<br /><br />Now, you need to know all of Netstat's various commands, so type:<br /><br /><b>netstat ?</b><br /><br />You will get something like this:<br /><br /><!--QuoteBegin--></div><table align="center" border="0" cellpadding="3" cellspacing="1" width="95%"><tbody><tr><td><b>QUOTE</b> </td></tr><tr><td id="QUOTE"><!--QuoteEBegin-->Displays protocol statistics and current TCP/IP network connections.<br /><br />NETSTAT [-a] [-e] [-n] [-s] [-p proto] [-r] [interval]<br /><br />-a Displays all connections and listening ports.<br />-e Displays Ethernet statistics. This may be combined with the -s option.<br />-n Displays addresses and port numbers in numerical form.<br />-p proto Shows connections for the protocol specified by proto; proto may be TCP or UDP. If used with the -s option to display per-protocol statistics, proto may be TCP, UDP, or IP.<br />-r Displays the routing table.<br />-s Displays per-protocol statistics. By default, statistics are shown for TCP, UDP and IP; the -p option may be used to specify a subset of the default.<!--QuoteEnd--></td></tr></tbody></table><div class="postcolor"><!--QuoteEEnd--><br /><br />Have a play around with the various options, but the most important use of these methods is when you combine them. The best command to use is<br /><br /><b>netstat -an</b><br /><br />because this will list all connections in Numerical Form, which makes it a lot easier to trace malicious users....Hostnames can be a little confusing if you don't know what you're doing (although they're easily understandable, as we shall see later). Also, by doing this, you can also find out what your own IP address is, which is always useful.<br /><br />Also,<br /><br /><b>netstat -b</b><br /><br />will tell you what ports are open and what programs are connecting to the internet.<br /><br /><b>## Types of Port ##</b><br /><br />It would be impossible to find out who was attacking you if computers could just access any old port to perform an important function; how could you tell a mail transfer from a Trojan Attack? Well, good news, because your regular, normal connections are assigned to low, commonly used ports, and in general, the higher the number used, the more you should be suspicious. Here are the three main types of port:<br /><br /><b># Well Known Ports</b>These run from 0 to 1023, and are bound to the common services that run on them (for example, mail runs on channel 25 tcp/udp, which is smtp (Simple Mail Transfer Protocol) so if you find one of these ports open (and you usually will), it's usually because of an essential function.<br /><br /><b># Registered Ports</b>These run on 1024 to 49151. Although not bound to a particular service, these are normally used by networking utilities like FTP software, Email client and so on, and they do this by opening on a random port within this range before communicating with the remote server, so don't panic (just be wary, perhaps) if you see any of these open, because they usually close automatically when the system that's running on them terminates (for example, type in a common website name in your browser with netstat open, and watch as it opens up a port at random to act as a buffer for the remote servers). Services like MSN Messenger and ICQ usually run on these Ports.<br /><br /><b># Dynamic/Private Ports</b>Ranging from 49152 to 65535, these things are rarely used except with certain programs, and even then not very often. This is indeed the usual range of the Trojan, so if you find any of these open, be very suspicious. So, just to recap:<br /><br /><!--QuoteBegin--></div><table align="center" border="0" cellpadding="3" cellspacing="1" width="95%"><tbody><tr><td><b>QUOTE</b> </td></tr><tr><td id="QUOTE"><!--QuoteEBegin-->Well Known Ports 0 to 1023 Commonly used, little danger.<br />Registered Ports 1024 to 49151 Not as common, just be careful.<br />Dynamic/Private Ports 49152 to 65535 Be extremely suspicious.<!--QuoteEnd--></td></tr></tbody></table><div class="postcolor"><!--QuoteEEnd--><br /><br /><b>## The hunt is on ##</b><br /><br />Now, it is essential that you know what you're looking for, and the most common way someone will attack your machine is with a Trojan. This is a program that is sent to you in an email, or attempts to bind itself to one of your ports, and when activated, it can give the user your passwords, access to your hard drive...they can even make your CD Tray pop open and shut. At the end of this Document, you will find a list of the most commonly used Trojans and the ports they operate on. For now, let's take another look at that first example of Netstat....<br /><br /><!--QuoteBegin--></div><table align="center" border="0" cellpadding="3" cellspacing="1" width="95%"><tbody><tr><td><b>QUOTE</b> </td></tr><tr><td id="QUOTE"><!--QuoteEBegin-->Active Connections<br /><br />Proto Local Address Foreign Address State<br />TCP macintosh: 27374 modem-123.tun.dialup.co.uk: 50505 ESTABLISHED<br />TCP macintosh: 80 proxy.webcache.eng.sq: 30101 TIME_WAIT<br />TCP macintosh MACINTOSH: 0 LISTENING<br />TCP macintosh MACINTOSH: 0 LISTENING<br />TCP macintosh MACINTOSH: 0 LISTENING<!--QuoteEnd--></td></tr></tbody></table><div class="postcolor"><!--QuoteEEnd--><br /><br />Now, straight away, this should make more sense to you. Your computer is connected on two ports, 80 and 27374. Port 80 is used for http/www transmissions (ie for all intents and purposes, its how you connect to the net, although of course it's a lot more complicated than that). Port 27374, however, is distinctly suspicious; first of all, it is in the registered port range, and although other services (like MSN) use these, let's assume that you have nothing at all running like instant messengers, webpages etc....you're simply connected to the net through proxy. So, now this connection is looking even more troublesome, and when you realise that 27374 is a common port for Netbus (a potentially destructive Trojan), you can see that something is untoward here. So, what you would do is:<br /><br /><!--QuoteBegin--></div><table align="center" border="0" cellpadding="3" cellspacing="1" width="95%"><tbody><tr><td><b>QUOTE</b> </td></tr><tr><td id="QUOTE"><!--QuoteEBegin-->1) run Netstat , and use:<br /><br />Netstat -a<br /><br />then<br /><br />Netstat -an<br /><br />So you have both Hostnames AND IP addresses.<!--QuoteEnd--></td></tr></tbody></table><div class="postcolor"><!--QuoteEEnd--><br /><br /><b>## Tracerouting ##</b><br /><br />Having the attacker's IP is all well and good, but what can you do with it? The answer is, a lot more! It's not enough to have the address, you also need to know where the attacker's connections are coming from. You may have used automated tracerouting tools before, but do you jknow how they work?<br /><br />Go back to MSDOS and type<br /><br /><!--QuoteBegin--></div><table align="center" border="0" cellpadding="3" cellspacing="1" width="95%"><tbody><tr><td><b>QUOTE</b> </td></tr><tr><td id="QUOTE"><!--QuoteEBegin-->tracert *type IP address/Hostname here*<!--QuoteEnd--></td></tr></tbody></table><div class="postcolor"><!--QuoteEEnd--><br /><br />Now, what happens is, the Traceroute will show you all the computers inbetween you and the target machine, including blockages, firewalls etc. More often than not, the hostname address listed before the final one will belong to the Hacker's ISP Company. It'll either say who the ISP is somewhere in there, or else you run a second trace on the new IP/hostname address to see who the ISP Company in question is. If the Hostname that you get back doesn't actually seem to mention an actual geographical location within its text, you may think all is lost. But fear not! Suppose you get a hostname such as<br /><br /><a href="http://www.haha.com/" target="_blank" rel="nofollow">http://www.haha.com</a><br /><br />Well, that tells us nothing, right? Wrong....simply enter the hostname in your browser, and though many times you will get nothing back, sometimes it will resolve to an ISP, and from there you can easily find out its location and in what areas they operate. This at least gives you a firm geographical location to carry out your investigations in.<br /><br />If you STILL have nothing, as a last resort you COULD try connecting to your target's ISP's port 13 by Telnet, which will tell you how many hours ahead or behind this ISP is of GMT, thus giving you a geographical trace based on the time mentioned (although bear in mind, the ISP may be doing something stupid like not having their clocks set correctly, giving you a misleading trace. Similarly, a common tactic of Hackers is to deliberately have their computer's clock set to a totally wrong time, so as to throw you off the scent). Also, unless you know what you're doing, I wouldn't advise using Telnet (which is outside the parameters of this tutorial).<br /><br /><b>## Reverse DNS Query ##</b><br /><br />This is probably the most effective way of running a trace on somebody. If ever you're in a chatroom and you see someone saying that they've "hacked into a satellite orbiting the Earth, and are taking pictures of your house right now", ignore them because that's just bad movie nonsense. THIS method is the way to go, with regard to finding out what country (even maybe what State/City etc) someone resides, although it's actually almost impossible to find an EXACT geographical location without actually breaking into your ISP's Head Office and running off with the safe.<br /><br />To run an rDNS query, simply go back to MS-DOS and type<br /><br /><b>netstat</b><br /><br />and hit return. Any active connections will resolve to hostnames rather than a numerical format.<br /><br /><b># DNS</b><br /><br />DNS stands for Domain Name Server. These are machines connected to the Internet whose job it is to keep track of the IP Addresses and Domain Names of other machines. When called upon, they take the ASCII Domain Name and convert it to the relevant numeric IP Address. A DNS search translates a hostname into an IP address....which is why we can enter "www.Hotmail.com" and get the website to come up, instead of having to actually remember Hotmail's IP address and enter that instead. Well, Reverse DNS, of course, translates the IP Address into a Hostname (ie - in letters and words instead of numbers, because sometimes the Hacker will employ various methods to stop Netstat from picking up a correct Hostname).<br /><br />So, for example,<br /><br />298.12.87.32 is NOT a Hostname.<br />mail6.bol.net.au IS a Hostname.<br /><br />Anyway, see the section at the end? (au) means the target lives in Australia. Most (if not all) hostnames end in a specific Country Code, thus narrowing down your search even further. If you know your target's Email Address (ie they foolishly sent you a hate mail, but were silly enough to use a valid email address) but nothing else, then you can use the Country codes to deduce where they're from as well. You can also deduce the IP address of the sender by looking at the emails header (a "hidden" line of code which contains information on the sender)...on Hotmail for example, go to Preferences, and select the "Full Header's Visible" option. Alternatively, you can run a "Finger" Trace on the email address, at:<br /><br />www.samspade.org<br /><br />Plus, some ISP's include their name in your Email Address with them too (ie Wanadoo, Supanet etc), and your Hacker may be using an email account that's been provided by a Website hosting company, meaning this would probably have the website host's name in the email address (ie Webspawners). So, you could use the information gleaned to maybe even hunt down their website (then you could run a website check as mentioned previously) or report abuse of that Website Provider's Email account (and thus, the Website that it goes with) to<br /><br />abuse@companynamegoeshere.com<br /><br />If your Hacker happens to reside in the USA, go to:<br /><br />www.usps.gov/ncsc/lookups/abbr_state.txt<br /><br />for a complete list of US State abbreviatons.<br /><br /><b>## List of Ports commonly used by Trojans ##</b><br /><br />Please note that this isn't a complete list by any means, but it will give you an idea of what to look out for in Netstat. Be aware that some of the lower Ports may well be running valid services.<br /><br />UDP: 1349 Back Ofrice DLL<br />31337 BackOfrice 1.20<br />31338 DeepBO<br />54321 BackOfrice 2000<br /><br /><br />TCP: 21 Blade Runner, Doly Trojan, Fore, Invisible FTP, WebEx, WinCrash<br />23 Tiny Telnet Server<br />25 Antigen, Email Password Sender, Haebu Coceda, Shtrilitz Stealth, Terminator, WinPC, WinSpy, Kuang2 0.17A-0.30<br />31 Hackers Paradise<br />80 Executor<br />456 Hackers Paradise<br />555 Ini-Killer, Phase Zero, Stealth Spy<br />666 Satanz Backdoor<br />1001 Silencer, WebEx<br />1011 Doly Trojan<br />1170 Psyber Stream Server, Voice<br />1234 Ultors Trojan<br />1243 SubSeven 1.0 - 1.8<br />1245 VooDoo Doll<br />1492 FTP99CMP<br />1600 Shivka-Burka<br />1807 SpySender<br />1981 Shockrave<br />1999 BackDoor 1.00-1.03<br />2001 Trojan Cow<br />2023 Ripper<br />2115 Bugs<br />2140 Deep Throat, The Invasor<br />2801 Phineas Phucker<br />3024 WinCrash<br />3129 Masters Paradise<br />3150 Deep Throat, The Invasor<br />3700 Portal of Doom<br />4092 WinCrash<br />4567 File Nail 1<br />4590 ICQTrojan<br />5000 Bubbel<br />5000 Sockets de Troie<br />5001 Sockets de Troie<br />5321 Firehotcker<br />5400 Blade Runner 0.80 Alpha<br />5401 Blade Runner 0.80 Alpha<br />5402 Blade Runner 0.80 Alpha<br />5400 Blade Runner<br />5401 Blade Runner<br />5402 Blade Runner<br />5569 Robo-Hack<br />5742 WinCrash<br />6670 DeepThroat<br />6771 DeepThroat<br />6969 GateCrasher, Priority<br />7000 Remote Grab<br />7300 NetMonitor<br />7301 NetMonitor<br />7306 NetMonitor<br />7307 NetMonitor<br />7308 NetMonitor<br />7789 ICKiller<br />8787 BackOfrice 2000<br />9872 Portal of Doom<br />9873 Portal of Doom<br />9874 Portal of Doom<br />9875 Portal of Doom<br />9989 iNi-Killer<br />10067 Portal of Doom<br />10167 Portal of Doom<br />10607 Coma 1.0.9<br />11000 Senna Spy<br />11223 Progenic trojan<br />12223 Hack´99 KeyLogger<br />12345 GabanBus, NetBus<br />12346 GabanBus, NetBus<br />12361 Whack-a-mole<br />12362 Whack-a-mole<br />16969 Priority<br />20001 Millennium<br />20034 NetBus 2.0, Beta-NetBus 2.01<br />21544 GirlFriend 1.0, Beta-1.35<br />22222 Prosiak<br />23456 Evil FTP, Ugly FTP<br />26274 Delta<br />30100 NetSphere 1.27a<br />30101 NetSphere 1.27a<br />30102 NetSphere 1.27a<br />31337 Back Orifice<br />31338 Back Orifice, DeepBO<br />31339 NetSpy DK<br />31666 BOWhack<br />33333 Prosiak<br />34324 BigGluck, TN<br />40412 The Spy<br />40421 Masters Paradise<br />40422 Masters Paradise<br />40423 Masters Paradise<br />40426 Masters Paradise<br />47262 Delta<br />50505 Sockets de Troie<br />50766 Fore<br />53001 Remote Windows Shutdown<br />54321 SchoolBus .69-1.11<br />61466 Telecommando<br />65000 Devil</div>Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-70319916986150172892010-10-05T04:23:00.000-07:002010-10-05T04:24:31.951-07:00What is TRP Ratings in the TV ChannelTelevision Rating Point (TRP) is a tool provided to judge which programmes are viewed the most. This gives us an index of the choice of the people and also the popularity of a particular channel. For calculation purpose, a device is attached to the TV set in a few thousand viewers’ houses for judging purpose. These numbers are treated as sample from the overall TV owners in different geographical and demographic sectors. The device is called as People’s Meter. It records the time and the programme that a viewer watches on a particular day. Then, the average is taken for a 30-day period which gives the viewership status for a particular channel.<br /><br />In the case of a TV advertisement that is aired 5 times reaching 50% of the gross audience with only 60% in the target audience, it would have 250 GRPs (= 5 x 50) -- ie, GRPs = reach x frequency - TRP in is this case should be 60% out of 250 GRPs = 150 TRPs - this is the rating point in the target, 60% of the gross rating.Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-32452351320433616202010-10-05T04:14:00.000-07:002010-10-05T04:16:52.167-07:00IP PortsPorts were developed so that computers could accept data from multiple sources over the same IP address. Think if it like this; Your TV service is the Internet, and the ports are you channels. You have many forms of entertainment, news, and information available through many different channels. Think about this, lets say that MTV is channel 35 on your TV. The same is true for web servers that run on port 80. Every port has a special purpose just as each channel serves a different television program. While you only have 1 cable TV subscription, you can still receive multiple channels.<br /><br />Two main types of ports: TCP and UDP. TCP stands for Transmission Control Protocol. UDP stands for User Data Protocol. Some programs on your computer will use TCP ports to communication and other may use UDP. It is important to know the difference between how the two operation. See TCP vs. UDP for an explanation with pictures!<br /><br />There are 65,535 TCP and UDP ports available to transmit data with. Ports 0-1023 are reserved for common use. These ports are assigned by the IANA (Internet Assigned Numbering Authority). This means, that every port from 0-1023 will be the same on every system. For example, let's say a server in New York is using port 80, and so is a server Texas. Because port 80 falls in the range of reserved ports, we know both servers are using port 80 for HTTP connections. Viewing a list of known ports can help you determine which type of connections are present on your machine. To see a list of commonly used port numbers and descriptions click here. For more information see the netstat article. You can view the RFC on ports (RFC 1700) here.<br /><br />Servers, or any machine for that matter "listen" on certain ports. For example, a server running web, FTP, and Telnet services will listen on a port for each. The act of listening simply means the machine is waiting for another device to connect to it. See the illustration below:<br /><br /><br /><br /><center> <img style="width: 361px; height: 202px;" src="http://www.skullbox.net/ports.gif" alt="" border="0" /> </center><br /><br />You can see how the server is listening for 3 ports over a single IP address (192.168.0.15). You should also know that it is possible for multiple devices to connect to a single port. Meaning, a telnet server may accept over 100 simultaneous connections to port 23.Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-21774995863320462992010-10-05T04:05:00.000-07:002010-10-05T04:08:28.652-07:00TCP vs UDP Which is BestThis article describes how TCP and UDP work, the difference between the two, and why you would choose one over the other.<br /><br />TCP (Transmission Control Protocol) is the most commonly used protocol on the Internet. The reason for this is because TCP offers error correction. When the TCP protocol is used there is a "guaranteed delivery." This is due largely in part to a method called "flow control." Flow control determines when data needs to be re-sent, and stops the flow of data until previous packets are successfully transferred. This works because if a packet of data is sent, a collision may occur. When this happens, the client re-requests the packet from the server until the whole packet is complete and is identical to its original.<br /><br />UDP (User Datagram Protocol) is anther commonly used protocol on the Internet. However, UDP is never used to send important data such as webpages, database information, etc; UDP is commonly used for streaming audio and video. Streaming media such as Windows Media audio files (.WMA) , Real Player (.RM), and others use UDP because it offers speed! The reason UDP is faster than TCP is because there is no form of flow control or error correction. The data sent over the Internet is affected by collisions, and errors will be present. Remember that UDP is <strong>only</strong> concerned with speed. This is the main reason why streaming media is not high quality.<br /><br /><br /><center> <img style="width: 391px; height: 261px;" src="http://www.skullbox.net/udp.jpg" alt="" border="0" /><br /><img style="width: 374px; height: 224px;" src="http://www.skullbox.net/tcp.jpg" alt="" border="0" /> </center><br /><br />On the contrary, UDP has been implemented among some trojan horse viruses. Hackers develop scripts and trojans to run over UDP in order to mask their activities. UDP packets are also used in DoS (Denial of Service) attacks. It is important to know the difference between TCP port 80 and UDP port 80. If you don't know what ports are go <a href="http://www.skullbox.net/ports.php">here</a>.<br /><br /><h4><em>Frame Structure</em></h4> As data moves along a network, various attributes are added to the file to create a <em>frame</em>. This process is called <em>encapsulation</em>. There are different methods of encapsulation depending on which protocol and <a href="http://www.skullbox.net/ntoplogy.php">topology</a> are being used. As a result, the frame structure of these packets differ as well. The images below show both the TCP and UDP frame structures.<br /><br /><center> <h2>TCP FRAME STRUCTURE</h2> <img style="width: 435px; height: 398px;" src="http://www.skullbox.net/diagrams/tcppacket.gif" alt="" border="0" /> <h2>UDP FRAME STRUCTURE</h2> <img style="width: 417px; height: 215px;" src="http://www.skullbox.net/diagrams/udppacket.gif" alt="" border="0" /> </center><br /><br />The <em>payload</em> field contains the actually data. Notice that TCP has a more complex frame structure. This is largely due to the fact the TCP is a connection-oriented protocol. The extra fields are need to ensure the "guaranteed delivery" offered by TCP.Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-23148489532571994402010-08-09T06:07:00.000-07:002010-08-09T06:08:28.803-07:00InterNet Protocol- IPIP (Internet Protocol) is the primary network protocol used on the Internet, developed in the 1970s. On the Internet and many other networks, IP is often used together with the Transport Control Protocol (TCP) and referred to interchangeably as TCP/IP.<br /><br />IP supports unique addressing for computers on a network. Most networks use the Internet Protocol version 4 (IPv4) standard that features IP addresses four bytes (32 bits) in length. The newer Internet Protocol version 6 (IPv6) standard features addresses 16 bytes (128 bits) in length.<br /><br />Data on an Internet Protocol network is organized into packets. Each IP packet includes both a header (that specifies source, destination, and other information about the data) and the message data itself.<br /><br />IP functions at layer 3 of the OSI model. It can therefore run on top of different data link interfaces including Ethernet and Wi-Fi.Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-43661514731200341172010-08-09T06:04:00.000-07:002010-08-09T06:06:19.501-07:00What is IPv6?<p>Internet Protocol Version 6 (IPv6) is a network layer protocol that enables data communications over a packet switched network. Packet switching involves the sending and receiving of data in packets between two nodes in a network. The working standard for the IPv6 protocol was published by the Internet Engineering Task Force (IETF) in 1998. The IETF specification for IPv6 is RFC 2460. IPv6 was intended to replace the widely used Internet Protocol Version 4 (IPv4) that is considered the backbone of the modern Internet. IPv6 is often referred to as the "next generation Internet" because of it's expanded capabilities and it's growth through recent large scale deployments. In 2004, Japan and Korea were acknowledged as having the first public deployments of IPv6.</p> <p>The explosive growth in mobile devices including mobile phones, notebook computers, and wireless handheld devices has created a need for additional blocks of IP addresses. IPv4 currently supports a maximum of approximately 4.3 billion unique IP addresses. IPv6 supports a theoretical maximum of 2128 addresses (340,282,366,920,938,463,463,374,607,431,768,211,456 to be exact!). Recent advancements in network technology including Network Address Translation (NAT) have temporarily lessened the urgency for new IP addresses, however, recent estimates indicate that IPv4 addresses could be exhausted as soon as 2012.</p> <p>IPv6 and IPv4 share a similar architecture. The majority of transport layer protocols that function with IPv4 will also function with the IPv6 protocol. Most application layer protocols are expected to be interoperable with IPv6 as well, with the notable exception of File Transfer Protocol (FTP). FTP uses embedded network layer addresses to facilitate data transmission. An IPv6 address consists of eight groups of four hexadecimal digits. If a group consists of four zeros, the notation can be shortened using a colon to replace the zeros.</p> <p>A main advantage of IPv6 is increased address space. The 128-bit length of IPv6 addresses is a significant gain over the 32-bit length of IPv4 addresses, allowing for an almost limitless number of unique IP addresses. The size of the IPv6 address space makes it less vulnerable to malicious activities such as IP scanning. IPv6 packets can support a larger payload than IPv4 packets resulting in increased throughput and transport efficiency.</p> <p>A key enhancement over IPv4 is native support for mobile devices. IPv6 supports the Mobile IPv6 (MIPv6) protocol which enables mobile devices to switch between networks and receive a roaming notification regardless of physical location. MIPv6 is a hallmark of the protocol and was specified as a firm requirement during the design of IPv6. The IETF has separate specifications for MIPv6 that detail data structure, messaging, and security requirements. </p> <p>Auto-configuration is another IPv6 enhancement that is considered a great benefit to network administrators. IPv6 devices can independently auto-configure themselves when connected with other IPv6 devices. Configuration tasks that can be carried out automatically include IP address assignment and device numbering. An IPv6 router has the ability to determine its own IPv6 address using data link layer addressing parameters. The IETF has issued RFC 2462 to set guidelines for IPv6 auto-configuration.</p> <p>The IPv6 protocol improves upon IPv4 with increased authentication and privacy measures. IPSec security is embedded into the IPv6 specification to manage encryption and authentication between hosts. This built in security framework enables secure data traffic between hosts that is independent of any applications on either host. In this way, IPv6 provides an efficient end to end security framework for data transfer at the host or the network level.</p> <p>The deployment of IPv6 networks is growing worldwide. Full replacement of IPv4 is expected to take some time, as it remains the most widely used Internet Protocol. The United States, China, and India are leading recent deployments of the IPv6 protocol and have large investments in IPv6 network infrastructure. The United States government has mandated that federal agencies must complete the transition to an IPv6 infrastructure no later than 2008. Software companies are also releasing operating systems that support the IPv6 standard. In 1997, IBM became the first commercial vendor to support IPv6 through its AIX 4.3 operating system. The latest version of Microsoft's Windows operating system, Windows Vista, has full IPv6 support enabled by default.</p>Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-81047753729375570342010-06-11T00:08:00.000-07:002010-06-11T00:10:22.569-07:00Tunneling<p> <img alt="" src="http://www.topbits.com/images/Article%20Images/Data%20Link%20Layer/Tunneling%20Protocols.gif" style="width: 150px; height: 184px;" align="left" /></p> <p> Tunneling is a way in which data is transferred between two networks securely. All the data that is being transferred are fragmented into smaller packets or frames and then passed through the tunnel. This process is different from a normal data transfer between nodes. Every frame passing through the tunnel will be encrypted with an additional layer of tunneling encryption and encapsulation which is also used for routing the packets to the right direction. This encapsulation would then be reverted at the destination with decryption of data which is later sent to the desired destined node.</p> <p> A tunnel is a logical path between the source and the destination endpoints between two networks. Every packet is encapsulated at the source will be de-capsulated at the destination. This process will keep happening as long as the logical tunnel is persistent between the two endpoints.</p> <h3> Tunneling Protocols</h3> <p> The Windows Server 2003 family supports the following tunneling protocols for secure communication:</p> <ul><li> Point-to-Point Tunneling Protocol (PPTP) <ul><li> PPTP employs user-level PPP authentication methods and Microsoft Point-to-Point Encryption (MPPE) for data encryption.</li><li> PPTP uses TCP1723 and Protocol 47 (GRE).</li><li> PPTP uses only NTLM authentication.</li><li> PPTP provides 56 bit or 128 bit Microsoft Point-to-Point Encryption (MPPE).</li></ul> </li><li> Layer Two Tunneling Protocol (L2TP) <ul><li> L2TP is an industry-standard Internet tunneling protocol with roughly the same functionality as the Point-to-Point Tunneling Protocol (PPTP). Based on the Layer Two Forwarding (L2F) and Point-to-Point Tunneling Protocol (PPTP) specifications, you can use L2TP to set up tunnels across intervening networks. Like PPTP, L2TP encapsulates Point-to-Point Protocol (PPP) frames, which then encapsulate IP or IPX protocols, allowing users to remotely run programs that are dependent on specific network protocols.</li><li> L2TP uses the UDP 1701.</li><li> L2TP does not provide any encryption by itself.</li></ul> </li><li> L2TP with Internet Protocol security (L2TP/IPSec) <ul><li> L2TP/IPSec employs user-level PPP authentication methods over a connection that is encrypted with IPSec. IPSec requires host authentication using either the Kerberos protocol, shared secret or computer-level certificates.</li><li> L2TP with IPSec uses UDP 500 = ISAKMP, Protocol 50 = Encapsulated Security Payload (ESP) and possibly Protocol 51 = Authentication Header (AH).</li><li> L2TP/IPSec uses both Mutual authentication and NTLM authentication.</li><li> IPSec provides DES (56 bit) and 3DES (168 bit) encryption.</li></ul> </li></ul> <h2> How Tunneling Works</h2> <p> As we know VPN connection are of two type, PPTP (Point-to-Point tunneling protocol) and L2TP (Layer 2 tunneling protocol). Both PPTP and L2TP tunnels are nothing but local sessions between two different endpoints. Incase they have to communicate then the tunneling type must be negotiated between the endpoint, either PPTP or L2TP and then more configurable parameters like encryption, address assignment, compression etc must be configured in order to get the best possible security over the internet based private logical tunnel communication. This communication is created, maintained and terminated using a tunnel management protocol.</p> <p> Data can be sent once the tunnel is in place and clients or server can use the same tunnel to send and receive data across the internetwork. The data transfer depends upon the tunneling protocols being used for the transfer. For example, whenever the client wants to send data or payload (the packets containing data) to the tunneling server, the tunnel server adds a header to each packet. This header packet contains the routing information which informs the packet about the destination across the internetwork communication. Once the payload is received at the destination, the header information is verified. After which destination tunnel server sends the packet to the destined node or client or server.</p> <h3> Point-to-Point Protocol (PPP)</h3> <p> It is very obvious that the PPTP and L2TP protocoasl arefully dependent upon PPP connection and it is very much important to understand and examine PPP a little more closely. Initially PPP was designed to work with only dial-up connections or dedicated connections. If the data transfer is happening over PPP connection, then the packets going over PPP are encapsulated within PPP frames and then send across or transmitted over to the destination dial-up or PPP server.</p> <p> There are four distinct phases of negotiation in a PPP connection. Each of these four phases must complete successfully before the PPP connection is ready to transfer user data.</p> <ul><li> Phase 1: PPP Link Establishment First step is where PPP uses the LCP or Link Control Protocol to connect to the destination network. Apart from establishing the connection, LCP is also responsible for maintaining and terminating the connection too. Take for example, during this phase 1, LCP connects to the destination and prepares the authentication protocol which will be used in phase 2. Next step would be to negotiate and find out if these two nodes in a PPP connection would agree on any compression or encryption algorithm. If the answer is yes then the same is be implemented in Phase 4.</li><li> Phase 2: A User Authentication Second step is where the user credentials are sent to the remote destination for authentication. There are different secure authentication program. The secure method of authentication must be used to safeguard the user credentials. If you are using PAP (password Authentication Protocol) for authorizing user credential, the user information is passed in plain clear text which can be captured easily. This is the only time when the user must take utmost care in handling his/her credential from any theft. If for any reason these credentials were captured by the intruder, and then once the user connection is authenticate, the intruder will traps the communication, disconnect the original user and takes control of the connection.</li><li> Phase 3: PPP Callback Control The Microsoft implementation of PPP includes an optional callback control phase. This phase uses the Callback Control Protocol (CBCP) immediately after the authentication phase. If configured for callback, both the remote client and NAS disconnect after authentication. The NAS then calls the remote client back at a specified phone number. This provides an additional level of security to dial-up connections. The NAS allows connections from remote clients physically residing at specific phone numbers only. Callback is only used for dial-up connections, not for VPN connections.</li><li> Phase 4: Invoking Network Layer Protocol(s) Once the previous phases have been completed, PPP invokes the various network control protocols (NCPs) that were selected during the link establishment phase (Phase 1) to configure protocols used by the remote client. For example, during this phase, IPCP is used to assign a dynamic address to the PPP client. In the Microsoft implementation of PPP, the Compression Control Protocol (CCP) is used to negotiate both data compression (using MPPC) and data encryption (using MPPE).</li></ul> <h3> Data-Transfer</h3> <p> Once the four phases of PPP negotiation have been completed, PPP begins to forward data to and from the two peers. Each transmitted data packet is wrapped in a PPP header that is removed by the receiving system. If data compression was selected in phase 1 and negotiated in phase 4, data is compressed before transmission. If data encryption is selected and negotiated, data is encrypted before transmission. If both encryption and compression are negotiated, the data is compressed first, and then encrypted.</p> <h3> Point-to-Point Tunneling Protocol (PPTP)</h3> <p> PPTP encapsulates PPP frames in IP datagram for transmission over an IP internetwork, such as the Internet. PPTP can be used for remote access and router-to-router VPN connections.</p> <p> PPTP or Point-to-Point tunneling protocol works over TCP port which is also used for tunnel management and GRE or Generic Routing Encapsulation protocol to encapsulat any PPP frames which will later be used in sending data through the tunnel. Compression or encryption will depend on the tunnel configuration.</p> <h3> Layer Two Tunneling Protocol (L2TP)</h3> <p> L2TP was first proposed by Cisco Systems Inc which used a combination Layer 2 Forwarding (L2F) with PPTP. The IP frames can be encapsulated by L2TP to be sent over X.25, FR (Frame Relay), ATM (Asynchronous Transfer Mode) networks. And L2TP based IP tunnel over the internet is the safest way of data transfer today which uses the compression and/or encryption as required to protect the data from intruders.</p>Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-81384338005368947232010-05-26T01:39:00.000-07:002010-05-26T01:41:32.028-07:00The Top Ten Harmfull Viruses & Anti Viruses<span style="font-family:verdana, helvetica, sans-serif;"><img style="height: 146px;" src="http://filipinoscribbles.files.wordpress.com/2010/01/computer-virus-bugs-clip-art-thumb3167674.jpg" width="250" height="276" /> </span><a rel="nofollow" title="Deadly Computer Viruses" target="_blank" href="http://www.elistmania.com/images/articles/132/Original/Deadly_Computer_Viruses.gif"><span style="font-family:verdana, helvetica, sans-serif;"><img alt="Deadly Computer Viruses" src="http://www.elistmania.com/images/articles/132/Thumbnail/Deadly_Computer_Viruses.gif" width="125" border="0" height="124" /></span></a><span style="font-family:verdana, helvetica, sans-serif;"> </span><span style="font-family:verdana, helvetica, sans-serif;"><img style="height: 141px;" src="http://www.cs.cornell.edu/courses/cs1130/2008fa/module1/assignments/a1computervirus/computer%20virus.jpg" width="114" height="213" /></span><span class="h2Class"> <div class="ImageBorder"> </div> <div class="Summary"><span style="font-family:verdana, helvetica, sans-serif;">In simple terms, a virus can aptly be called a virtual disease which affects a computer system and makes it sick, forcing to act in a manner undesired by the user. No good deed goes unpunished, and with the joys and leisure that were brought by the computer, along came the viruses to ruin all the fun. There are billions of viruses out there, big and small. But there were some that stood out and ruined things for us in a spectacular fashion. Below is a list of 10 of the deadliest virus which create havoc in the virtual as well as the real world.<br /><br /></span><span class="h2Class"><div class="Summary"> <div class="Summary"> <div class="h2Class2"> <h2><span style="font-family:verdana, helvetica, sans-serif;">I love you</span></h2></div></div></div> <div class="Summary"> </div> <div class="Summary"> </div> <div class="Steps"> <div class="stepBox"> <div class="stepContentBoxStill"> <div class="Borders"> <div class="Img"><a rel="nofollow" title="I love you" target="_blank" href="http://www.elistmania.com/images/articles/132/Original/I_love_you.jpg"><span style="font-family:verdana, helvetica, sans-serif;"><img alt="I love you" src="http://www.elistmania.com/images/articles/132/Thumbnail/I_love_you.jpg" border="0" /></span></a><span style="font-family:verdana, helvetica, sans-serif;"> </span> </div> </div> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;">The three words that can at most motivate you to cross the seven seas - or at least tempt you to open en email. This very temptation was the downfall of many computer users when this multipurpose- multi skilled virus hit the web. It had the ability to replicate itself via IRC chat and email, transfer and hide itself in different files and folders, and infect the registry keys once you opened an email in you inbox declaring “I Love You”. The virus thought to be originated somewhere in the Philippines, caused damage which was estimated to be around $8-10 billion.</span></div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;"> </span></div> <div class="Summery" style="text-align: left;"> <div class="h2Class2"> <h2><span style="font-family:verdana, helvetica, sans-serif;">Melissa</span></h2></div></div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"> </div></div></div> <div class="stepBox"> <div class="stepContentBoxStill"> <div class="Borders"> <p class="Img" align="center"><a rel="nofollow" title="Melissa" target="_blank" href="http://www.elistmania.com/images/articles/132/Original/Melissa.jpg"><span style="font-family:verdana, helvetica, sans-serif;"><img alt="Melissa" src="http://www.elistmania.com/images/articles/132/Thumbnail/Melissa.jpg" border="0" /></span></a></p></div> <div class="Img"> </div> <div class="Img"> </div> <div class="Img"> </div> </div> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;">The creator of this virus received a 20 month jail sentence and a $5000 fine. Generated over a decade ago, this clever piece of virtual disease operated through Microsoft Outlook. This is how it worked: you receive an email titled “Here is the Document you asked for” from an unknown sender, you got infected as soon as you opened the email, and the virus would replicate and delivers itself to the top 50 people on your list without you getting a hint of it. Some major US government departments were hit and the damage is thought to be around $1 billion at least. A 20 month jail sentence well deserved.</span></div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;"><span class="h2Class"> </span> </span> <div class="h2Class2" style="height: 42px;"> <h2><span style="font-family:verdana, helvetica, sans-serif;">MyDoom</span></h2></div></div></div></div> <div class="stepBox"> <div class="stepContentBoxStill"> <div class="Borders"> <div class="Img"> </div> <div class="Img"> </div> <div class="Img"> </div> <div class="Img"> </div> <div class="Img"> </div> <p class="Img" align="center"><a rel="nofollow" title="MyDoom" target="_blank" href="http://www.elistmania.com/images/articles/132/Original/MyDoom.gif"><span style="font-family:verdana, helvetica, sans-serif;"><img alt="MyDoom" src="http://www.elistmania.com/images/articles/132/Thumbnail/MyDoom.gif" border="0" /></span></a></p></div> <div class="Img"> </div> <div class="Img"> </div> <div class="Img"> </div> <div class="Img"><span style="font-family:verdana, helvetica, sans-serif;"> </span></div> </div> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;">MyDoom was instigated somewhere in mid 2004 and it actually prompted US senator to propose the creation of a “National Virus Response Centre”. The virus attacked in two phases; the first phase infected different Operating Systems, creating inroads and backdoors and making them vulnerable to external users. Once this problem was sorted out, the MyDoom struck again after few months, this time targeting the Search Engines like Google, slowing them down considerably, and crashing a few.</span></div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"><span class="h2Class"></span> </div></div> <div class="stepBox"> <div class="stepContentBoxStill"> <div class="stepTitle"> <div class="h2Class2" style="height: 47px;"> <h2><span style="font-family:verdana, helvetica, sans-serif;">Nimda</span></h2></div></div> <div class="Borders"> <div class="Img"> </div> <div class="Img"> </div> <div class="Img"> </div> <div class="Img"> </div> <p class="Img" align="center"><a rel="nofollow" title="Nimda" target="_blank" href="http://www.elistmania.com/images/articles/132/Original/Nimda.jpg"><span style="font-family:verdana, helvetica, sans-serif;"><img alt="Nimda" src="http://www.elistmania.com/images/articles/132/Thumbnail/Nimda.jpg" border="0" /></span></a></p></div> <p class="Img" align="center"> </p></div> </div> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;">Spell it backwards and you will understand its prime targets: yes, the ‘Admin’ and servers. It was basically a worm and has the record of being the fastest ever virus to spread; it took only 22 minutes to break into the list of top ten most deadly viruses of all times. It basically targeted internet servers and websites, creating a mass crater through which thousands of computers were affected at the same time. Once infected, the systems became exposed to open attacks by the outsiders. </span></div> <div class="Summery" style="text-align: left;"> </div> <div class="stepBox"> <div class="stepContentBoxStill"> <div class="stepTitle"><span style="font-family:verdana, helvetica, sans-serif;"> </span> <div class="h2Class2"> <h2><span style="font-family:verdana, helvetica, sans-serif;">Code Red</span></h2></div></div> <div class="Borders"> <div class="Img"> </div> <div class="Img"> </div> <div class="Img"> </div> <div class="Img"> </div> <div class="Img"> </div> <p class="Img" align="center"><a rel="nofollow" title="Code Red" target="_blank" href="http://www.elistmania.com/images/articles/132/Original/Code_Red.jpg"><span style="font-family:verdana, helvetica, sans-serif;"><img alt="Code Red" src="http://www.elistmania.com/images/articles/132/Thumbnail/Code_Red.jpg" border="0" /></span></a></p></div> <p class="Img" align="center"> </p></div> <p class="Img" align="center"> </p></div> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;">Damages of almost $200 million a day, and affecting the computers inside the White House are the degree of achievements of this virus. It subjugated the Windows by acting as a buffer overflow, sending humongous amount of information to the computer so that it spilt over, eventually forcing a shut down by overlapping the memory of the computers. The problem wasn’t solved until Microsoft issued a revival package to cater for this virus. </span></div> <div class="Summery" style="text-align: left;"> </div> <div class="stepBox"> <div class="stepContentBoxStill"> <div class="stepTitle"><span class="h2Class"> <div class="h2Class2"> <h2><span style="font-family:verdana, helvetica, sans-serif;">SQL Slammer/Saphire</span></h2></div></span></div> <div class="stepTitle"> </div> <div class="stepTitle"> </div> <div class="Borders"> <p class="Img" align="center"><a rel="nofollow" title="SQL Slammer/Saphire" target="_blank" href="http://www.elistmania.com/images/articles/132/Original/SQL_Slammer_Saphire.jpg"><span style="font-family:verdana, helvetica, sans-serif;"><img alt="SQL Slammer/Saphire" src="http://www.elistmania.com/images/articles/132/Thumbnail/SQL_Slammer_Saphire.jpg" border="0" /></span></a></p></div> <div class="Img"> </div> <div class="Img"> </div> </div> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;">Another swiftly spreading virus, it hit 75,000 computers in the first 10 minutes of its inception, taking down and severely damaging numerous American Banks, Security systems and organizations, and Airline networks. And the virus wasn’t just privy to the US; it ruthlessly damaged the internet capacity of South Korea for at least half a day. The damage was estimated around at least a billion dollars. </span></div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;"> </span></div> <div class="Summery" style="text-align: left;"> <div class="h2Class2"> <h2><span style="font-family:verdana, helvetica, sans-serif;">Storm Worm</span></h2></div></div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"> </div></div> <div class="stepBox"> <div class="stepContentBoxStill"> <div class="Borders"> <p class="Img" align="center"><a rel="nofollow" title="Storm Worm" target="_blank" href="http://www.elistmania.com/images/articles/132/Original/Storm_Worm.jpg"><span style="font-family:verdana, helvetica, sans-serif;"><img alt="Storm Worm" src="http://www.elistmania.com/images/articles/132/Thumbnail/Storm_Worm.jpg" border="0" /></span></a></p></div> <p class="Img" align="center"> </p></div> <p class="Img" align="center"> </p></div> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;">One of the latest and most recent viruses to strike the internet, the Storm Worm employed a similar strategy to the one used by the Melissa; the mail’s title mentioned a current natural disaster like an earthquake (but most often a storm). Once the email was opened, the virus spread around like wild fire, affecting registries and documents across the hard disk. It turned out to be a mother-virus, instigating numerous hidden programs in the background which made the PC vulnerable and enticing to hackers. </span></div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"> <div class="h2Class2"> <h2><span style="font-family:verdana, helvetica, sans-serif;">Klez</span></h2></div></div> <div class="stepBox"> <div class="stepContentBoxStill"> <div class="stepTitle"><span style="font-family:verdana, helvetica, sans-serif;"> </span></div> <div class="stepTitle"> </div> <div class="stepTitle"> </div> <div class="stepTitle"> </div> <div class="stepTitle"> </div> <div class="Borders"> <p class="Img" align="center"><a rel="nofollow" title="Klez" target="_blank" href="http://www.elistmania.com/images/articles/132/Original/Klez.jpg"><span style="font-family:verdana, helvetica, sans-serif;"><img alt="Klez" src="http://www.elistmania.com/images/articles/132/Thumbnail/Klez.jpg" border="0" /></span></a></p></div> <p class="Img" align="center"> </p></div> <p class="Img" align="center"> </p></div> <p class="Img" align="center"> </p> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;">With the mix characteristics of a virus, worm and a Trojan horse, Klez gave the antivirus programs a real headache by simply disabling them and making them look like a joke. However this is only the beginning of its trickery; after it was thought it be defeated, it was taken over, decoded and customized by black hat hackers (hackers who specialize in unauthorized penetration) . Its ability was enhanced by providing it with the capability to "spoof" from the user's address book and make it look like that an email came from them, increasing the chances of the receiver opening the email and becoming the next casualty. </span></div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"><strong><span style="font-family:verdana, helvetica, sans-serif;font-size:130%;">Sasser</span></strong></div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"> </div> <p class="Summery" style="text-align: left;" align="center"><span style="font-family:verdana, helvetica, sans-serif;"> </span><a rel="nofollow" title="Sasser" target="_blank" href="http://www.elistmania.com/images/articles/132/Original/Sasser.jpg"><span style="font-family:verdana, helvetica, sans-serif;"><img alt="Sasser" src="http://www.elistmania.com/images/articles/132/Thumbnail/Sasser.jpg" border="0" /></span></a> </p> <div class="stepBox"> <div class="stepContentBoxStill"> <div class="stepTitle"><span class="h2Class"></span> </div> <div class="Borders"> <div class="Img"><span style="font-family:verdana, helvetica, sans-serif;"> </span> </div> </div> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;">Damaging the computer through network ports, Sasser mostly targeted Windows 2000 and XP. It’s main casualties were the news agency Agence France-Presse (AFP) which had all its satellite communications jammed for hours , U.S. Airlines which had to reschedule its flights because of the worm had depleted their computers, a Finnish insurance company which was forced to close down 130 of its offices on emergency basis, Goldman Sachs, and Deutsche Post were all badly affected as well. However its unique feature was that it did not spread through emails, but rather observed computers and kept a look out for their vulnerabilities. On the basis of its knowledge, it would scan random IP addresses from the database and send itself to the next victim.</span></div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"> </div> <div class="Summery" style="text-align: left;"> <div class="h2Class2"> <h2><span style="font-family:verdana, helvetica, sans-serif;">Autorun</span></h2></div></div> <div class="Summery" style="text-align: left;"> </div></div> </div> <div class="stepBox"> <div class="stepContentBoxStill"> <div class="stepTitle"><span class="h2Class"></span> </div> <div class="Borders"> <p class="Img" align="center"><a rel="nofollow" title="Autorun" target="_blank" href="http://www.elistmania.com/images/articles/132/Original/Autorun.jpg"><span style="font-family:verdana, helvetica, sans-serif;"><img alt="Autorun" src="http://www.elistmania.com/images/articles/132/Thumbnail/Autorun.jpg" border="0" /></span></a></p></div> <p class="Img" align="center"> </p></div> <p class="Img" align="center"> </p></div> <div class="Summery" style="text-align: left;"><span style="font-family:verdana, helvetica, sans-serif;">This virus primarily targeted USBs and flash drives and established them as its major source of movement and propagation. It affected networks and all the computers present on them. Once affected, the folder options would be disabled, the task manager too would be unavailable and the virus itself would become the system administrator. The virus would replicate itself in all the folders, therefore eating up useful space on the hard disk and making it eventually extremely slow. The loss was in terms of useful data on millions of computers across the world. </span></div></span><span style="font-family:verdana, helvetica, sans-serif;"><br /><br /><br /></span></div></span>Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-55189875968675458252010-04-16T02:21:00.000-07:002010-04-16T02:23:02.403-07:00What is Database<p> One of the technology terms that most people have become accustomed to hearing either at work or while surfing the internet is the database. The database used to be an extremely technical term, however with the rise of computer systems and information technology throughout our culture, the database has become a household term.</p> <p> The definition of a database is a structured collection of records or data that is stored in a computer system. In order for a database to be truly functional, it must not only store large amounts of records well, but be accessed easily. In addition, new information and changes should also be fairly easy to input. In order to have a highly efficient database system, you need to incorporate a program that manages the queries and information stored on the system. This is usually referred to as DBMS or a Database Management System. Besides these features, all databases that are created should be built with high data integrity and the ability to recover data if hardware fails.</p> <h2> Types of Databases</h2> <p> There are several common types of databases; each type of database has its own data model (how the data is structured). They include; Flat Model, Hierarchical Model, Relational Model and Network Model.</p> <h2> The Flat Model Database</h2> <p> In a flat model database, there is a two dimensional (flat structure) array of data. For instance, there is one column of information and within this column it is assumed that each data item will be related to the other. For instance, a flat model database includes only zip codes. Within the database, there will only be one column and each new row within that one column will be a new zip code.</p> <h2> The Hierarchical Model Database</h2> <p> The hierarchical model database resembles a tree like structure, such as how Microsoft Windows organizes folders and files. In a hierarchical model database, each upward link is nested in order to keep data organized in a particular order on a same level list. For instance, a hierarchal database of sales, may list each days sales as a separate file. Within this nested file are all of the sales (same types of data) for the day.</p> <h2> The Network Model</h2> <p> In a network model, the defining feature is that a record is stored with a link to other records - in effect networked. These networks (or sometimes referred to as pointers) can be a variety of different types of information such as node numbers or even a disk address.</p> <h2> The Relational Model</h2> <p> The relational model is the most popular type of database and an extremely powerful tool, not only to store information, but to access it as well. Relational databases are organized as tables. The beauty of a table is that the information can be accessed or added without reorganizing the tables. A table can have many records and each record can have many fields.</p> <p> Tables are sometimes called a relation. For instance, a company can have a database called customer orders, within this database will be several different tables or relations all relating to customer orders. Tables can include customer information (name, address, contact, info, customer number, etc) and other tables (relations) such as orders that the customer previously bought (this can include item number, item description, payment amount, payment method, etc). It should be noted that every record (group of fields) in a relational database has its own primary key. A primary key is a unique field that makes it easy to identify a record.</p> <p> Relational databases use a program interface called SQL or Standard Query Language. SQL is currently used on practically all relational databases. Relational databases are extremely easy to customize to fit almost any kind of data storage. You can easily create relations for items that you sell, employees that work for your company, etc.</p> <h2> Accessing Information Using a Database</h2> <p> While storing data is a great feature of databases, for many database users the most important feature is quick and simple retrieval of information. In a relational database, it is extremely easy to pull up information regarding an employee, but relational databases also add the power of running queries. Queries are requests to pull specific types of information and either show them in their natural state or create a report using the data. For instance, if you had a database of employees and it included tables such as salary and job description, you can easily run a query of which jobs pay over a certain amount. No matter what kind of information you store on your database, queries can be created using SQL to help answer important questions.</p> <h2> Storing a Database</h2> <p> Databases can be very small (less than 1 MB) or extremely large and complicated (terabytes as in many government databases), however all databases are usually stored and located on hard disk or other types of storage devices and are accessed via computer. Large databases may require separate servers and locations, however many small databases can fit easily as files located on your computer's hard drive.</p> <h2> Securing a Database</h2> <p> Obviously, many databases store confidential and important information that should not be easily accessed by just anyone. Many databases require passwords and other security features in order to access the information. While some databases can be accessed via the internet through a network, other databases are closed systems and can only be accessed on site.</p>Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-50115481473621559652010-04-16T02:17:00.000-07:002010-04-16T02:19:42.289-07:00UnderStanding Systems Management Server (SMS)<h2>Systems Management Server (SMS) Overview</h2> <p>SMS 2.0 is a Microsoft BackOffice systems management tool that can both operate in and manage an assortment of network environments. Systems Management Server (SMS) enables network environments and network resources to be centrally controlled. The core control point or center of Systems Management Server is the SMS Administrator console. This is a snap-in to the Microsoft Management Console (MMC). The industry standard for Web-Based Enterprise Management (WBEM) is the core of SMS data collection and presentation.</p> <p>The main functions of SMS are listed here:</p> <ul><li> <p>Resource discovery</p> </li><li> <p>Hardware and software inventory</p> </li><li> <p>Software distribution</p> </li><li> <p>Software metering</p> </li><li> <p>Network Analysis</p> </li><li> <p>Remote support through the Remote Tools feature</p> </li></ul> <p>The SMS Administrator console is used to access and initiate these SMS 2.0 functions. A process known as resource discovery must be performed first to find computers, network hardware, and groups and users.</p> <p>The main SMS components are listed here:</p> <ul><li> <p>SMS site: A SMS site specifies the computers, other networking hardware, users and groups, and all resources which will be managed through SMS. The SMS environment is made up of one or multiple SMS sites. You define a SMS site based on IP subnet address.</p> </li></ul> <p>An SMS site consists of the following SMS components</p> <ul><li> <p>SMS site server</p> </li><li> <p>SMS site systems</p> </li><li> <p>SMS clients and resources</p> </li></ul> <p>The structure that links multiple sites together is called a hierarchy. The hierarchy is created by linking sites together so that parent-child relationships can be formed:</p> <ul><li> <p>Parent site: This is a SMS site that contains one or multiple additional site beneath it.</p> </li><li> <p>Child site: This is a SMS site that has a parent site residing over it in the hierarchy.</p> </li></ul> <p>There are also two different types of sites that assist in organizing the administration of the SMS environment:</p> <ul><li> <p>Primary site</p> </li><li> <p>Secondary site</p> </li></ul> <p>SMS site server: This is the Windows server on which SMS 2.0 is installed and running. The SMS site server is the main access point between the SMS database and administrators. The SMS server manages the SMS site and component attributes. The SMS site server must be installed on a domain controller or on a member server. It cannot be installed on a stand-alone server.</p> <p>SMS site system: This is a Windows server that carries out one of multiple SMS roles for the SMS site. When installing SMS, the default configuration is that all SMS roles are installed on an SMS site server.</p> <p>The SMS roles are:</p> <ul><li> <p>Logon points: This is a SMS site system that is the initial connection point between a SMS site and client computer. Functions performed by logon point includes:</p> <ul><li> <p>Collection of discovery information on the client.</p> </li><li> <p>Determines the site assignment of the client.</p> </li><li> <p>Pass the client a list of client access points (CAPs).</p> </li></ul> </li><li> <p>Client access points (CAPs): This is a SMS site system that operates as the exchange point between SMS clients and the SMS site server. At the CAP; inventory, and status information and discovery information is gathered. Advertisement information can be retrieved from the CAP.</p> </li><li> <p>Distribution points: This is a SMS site system that installs the following components which deal with running a package at a SMS client computer:</p> <ul><li> <p>Package files</p> </li><li> <p>Programs</p> </li><li> <p>Scripts</p> </li></ul> </li><li> <p>Software metering servers: This is a SMS site system which enables administrators to perform a number of management activities:</p> <ul><li> <p>Grant/deny licenses for applications running on an SMS client.</p> </li><li> <p>Monitor and track application usage on SMS clients.</p> </li><li> <p>Restrict application usage on SMS clients.</p> </li></ul> </li><li> <p>SMS client: This is a computer running a Microsoft operating system listed below. A SMS client is installed through the SMS client component software, an is assigned to a SMS site.</p> <ul><li> <p>Microsoft Windows Server 2003</p> </li><li> <p>Windows XP Professional</p> </li><li> <p>Microsoft Windows 2000</p> </li><li> <p>Microsoft Windows NT 4.0</p> </li><li> <p>Microsoft Windows NT 3.51, Service Pack 5 or above.</p> </li><li> <p>Microsoft Windows 98</p> </li><li> <p>Microsoft Windows 95</p> </li></ul> </li></ul>Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-46120183075286952802010-04-16T02:13:00.000-07:002010-04-16T02:15:33.056-07:00How To Flush DNS<p> Most DNS clients cache the results of name resolution requests. This means that the DNS clients will temporarily store the website names that you have been visiting lately. This process speeds up name resolution if multiple lookups are done to the same address, such as is common when browsing the web. Hence, if you visit Yahoo.com second time, the DNS client will already have the name mapped and hence will retrieve the mapping quickly.</p> <p> Sometimes a bad DNS entry will be cached and you will need to either flush the DNS cache to get rid of it, or wait up to 24 hours for it to be dropped from the cache automatically. Given below is a comprehensive step-by-step process to flush the DNS.</p> <h2> How to Flush DNS in Microsoft Windows</h2> <p> In Microsoft Windows, you can use the command <strong>ipconfig /flushdns</strong> to flush the DNS resolver cache. Open the command prompt and type the following:</p> <p> <code>C:\>ipconfig /flushdns<br /> Windows IP Configuration<br /> Successfully flushed the DNS Resolver Cache.</code></p> <p> <code><input alt="" src="http://www.topbits.com/images/Article%20Images/networking%20misc/flush-dns.jpg" type="image" width="354" height="64"></code></p> <p> The above command will completely flush the DNS, deleting any incorrect entries too. You can also use the command <strong>ipconfig /displaydns</strong> to view the DNS resolver cache.</p> <p> <input alt="" src="http://www.topbits.com/images/Article%20Images/networking%20misc/ipconfig-displaydns.jpg" type="image"></p> <h2> Turning Off DNS Caching under Microsoft Windows</h2> <p> If you experience frequent issues with DNS caching under Microsoft Windows, you can disable client-side DNS caching with either of these two commands:</p> <p> <code>net stop dnscache<br /> sc servername stop dnscache </code></p> <p> This will disable DNS caching until the next reboot. To make the change permanent, use the Service Controller tool or the Services tool to set the DNS Client service startup type to Disabled. You can permanently disable DNS Client by following the below steps:</p> <ul><li> Goto <strong>Start</strong> and click on <strong>Run</strong>.</li><li> Type <strong>Services.msc </strong>in the <strong>Run </strong>command box.</li><li> A window listing all the services will popup. Search for a service called <strong>DNS Client. </strong></li><li> Double click on the listed <strong>DNS Client </strong>service and click <strong>Stop. </strong>Similarly, you can restart it by clicking <strong>Start. </strong></li></ul> <h2> Tuning DNS Caching under Microsoft Windows</h2> <p> You can modify the behavior of the Microsoft Windows DNS caching algorithm by setting two registry entries in the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters registry key.</p> <p> The MaxCacheTtl represents the maximum time that the results of a DNS lookup will be cached. The default value is 86,400 seconds. If you set this value to 1, DNS entries will only be cashed for a single second.</p> <p> MaxNegativeCacheTtl represents the maximim time that the results of a failed DNS lookup will be cached. The default value is 900 seconds. If you set this value to 0, failed DNS lookups will not be cached.</p> <h2> Flush DNS in Mac OSX</h2> <p> In Mac OSX Leopard, you can use the command <strong>dscacheutil -flushcache</strong> to flush the DNS resolver cache:</p> <p> <code>bash-2.05a$ dscacheutil -flushcache</code></p> <p> In Mac OSX versions 10.5.1 and before, the command <strong>lookupd -flushcache</strong> performed the same task:</p> <p> <code>bash-2.05a$ lookupd -flushcache</code></p> <h2> Flush DNS in Linux</h2> <p> In Linux, the nscd daemon manages the DNS cache. To flush the DNS cache, restart the nscd daemon. To restart the nscd daemon, use the command `<strong>/etc/init.d/nscd restart</strong>`.</p>Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-15745356383585083422010-03-17T06:03:00.000-07:002010-03-17T06:06:48.958-07:00What is VPN (Virtual Private Networking)?VPN gives extremely secure connections between private networks linked through the Internet. It allows remote computers to act as though they were on the same secure, local network.<br /><br />Advantages<br /><br /> * Allows you to be at home and access your company's computers in the same way as if you were sitting at work.<br /> * Almost impossible for someone to tap or interfer with data in the VPN tunnel.<br /> * If you have VPN client software on a laptop, you can connect to your company from anywhere in the world.<br /><br />Disadvantages<br /><br /> * Setup is more complicated than less secure methods. VPN works across different manufacturers' equipment, but connecting to a non-NETGEAR product will add to difficulty, since there may not documentation specific to your situation.<br /> * The company whose network you connect to may require you to follow the company's own policies on your home computers ( ! )<br /><br />VPN goes between a computer and a network (client-to-server), or a LAN and a network using two routers (server-to-server). Each end of the connection is an VPN "endpoint", the connection between them is a "VPN tunnel". When one end is a client, it means that computer is running VPN client software such as NETGEAR's ProSafe VPN Client. The two types of VPN:<br /><br /><p><b>VPN Client-to-Server (Client-to-Box):</b></p> <p> </p> <p><img style="width: 423px; height: 270px;" alt="Image" src="http://kbserver.netgear.com/media/images/answer_1128/clienttobox.jpg" border="0" /></p> <p><b>VPN Server-to-Server (Box-to-Box):</b></p> <p> </p> <p><img style="width: 411px; height: 238px;" alt="Image" src="http://kbserver.netgear.com/media/images/answer_1128/boxtobox.jpg" border="0" /></p> <p>All NETGEAR routers support "VPN Passthrough", but "passthrough" simply means the router does not stop VPN traffic — you still need two endpoints.</p><p><br /></p><p>The whole purpose of VPN is to prevent data being altered, so, for example, a passthrough router that is also running NAT will break the VPN connection.<br /><br />NETGEAR Support will configure one VPN tunnel between two pieces of NETGEAR equipment to demonstrate that the equipment and VPN work. For other information:<br /><br /> * See the list of NETGEAR VPN documentation in VPN Configuration and Troubleshooting Resources.<br /> * Read the product's Reference Manuals, available with the product's downloads.<br /> * Make use of NETGEAR's cost-effective ProSupport. This support for advanced features is available by phone, or with an on-site NETGEAR representative.<br /><br /></p>Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-59028797779123132912010-01-07T05:24:00.000-08:002010-01-07T05:26:31.414-08:00What is WiFi?Wi-Fi, which stands for wireless fidelity, in a play on the older term Hi-Fi, is a wireless networking technology used across the globe. Wi-Fi refers to any system that uses the 802.11 standard, which was developed by the Institute of Electrical and Electronics Engineers (IEEE) and released in 1997. The term Wi-Fi, which is alternatively spelled WiFi, Wi-fi, Wifi, or wifi, was pushed by the Wi-Fi Alliance, a trade group that pioneered commercialization of the technology.<br /><br />In a Wi-Fi network, computers with wifi network cards connect wirelessly to a wireless router. The router is connected to the Internet by means of a modem, typically a cable or DSL modem. Any user within 200 feet or so (about 61 meters) of the access point can then connect to the Internet, though for good transfer rates, distances of 100 feet (30.5 meters) or less are more common. Retailers also sell wireless signal boosters that extend the range of a wireless network.<br /><br />Wifi networks can either be "open", such that anyone can use them, or "closed", in which case a password is needed. An area blanketed in wireless access is often called a wireless hotspot. There are efforts underway to turn entire cities, such as San Francisco, Portland, and Philadelphia, into big wireless hotspots. Many of these plans will offer free, ad-supported service or ad-free service for a small fee. San Francisco recently chose Google to supply it with a wireless network.<br /><br />Wifi technology uses radio for communication, typically operating at a frequency of 2.4GHz. Electronics that are "WiFi Certified" are guaranteed to interoperate with each other regardless of brand. Wifi is technology designed to cater to the lightweight computing systems of the future, which are mobile and designed to consume minimal power. PDAs, laptops, and various accessories are designed to be wifi-compatible. There are even phones under development that would switch seamlessly from cellular networks to wifi networks without dropping a call.Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-19964233949256121062010-01-06T02:24:00.000-08:002010-01-06T02:25:40.445-08:00Upgrading to Windows 7: what XP and Vista users need to knowLast week, Microsoft finally announced that there would be six editions of Windows 7, just like there were for Windows XP and Windows Vista. The company will release Windows 7 Starter (worldwide only via OEMs), Windows 7 Home Basic (only in emerging markets), Windows 7 Home Premium (retail and OEM), Windows 7 Professional (retail and OEM), Windows 7 Ultimate Edition (retail only during promotions and OEM), and Windows 7 Enterprise (volume licenses).<br /><br />However, as part of its initiative to simplify the lineup, the software giant will only market Home Premium and Professional to average users. Most will be getting Windows 7 with their next purchase of a desktop, notebook, or netbook. (Speaking of netbooks, Microsoft also noted last week that all editions of Windows 7 will work on netbooks and it will be up to the OEM's discretion as to what editions they want to offer on each product.)<br /><br />If you won't be going through an OEM, you'll either want to purchase a full retail copy of Windows 7, a cheaper upgrade edition, or the OEM version (usually the cheapest and best way). While Microsoft has not given details on pricing for any of the three, the company has agreed to offer upgrade options to both Windows XP and Windows Vista users, and they are worth outlining in detail.<br />From Windows XP to Windows 7<br /><br />Information here is still a bit murky because Microsoft has not specified which XP editions will be eligible. The good news is that the company has confirmed that users currently running Windows XP will be able to buy the cheaper upgrade option of Windows 7. However, they will only be able to perform a clean install. The hassle of backing up applications and user data will fall on the user; the upgrade process will not backup anything.<br /><br />That may come as a shock to some, but Microsoft typically lets users purchase the cheaper upgrade option by owners of the last two releases of Windows (in this case XP and Vista) but the older of the two operating systems usually require a clean install.<br />From Windows Vista to Windows 7<br /><br />Microsoft will only allow the following upgrade paths to Vista users. For example, users who purchase an upgrade copy of Windows 7 Professional and have Vista Home Premium will only be able to perform a clean install. Here's the migration list:<br /><br /> * Windows Vista Home Premium to Windows 7 Home Premium<br /> * Windows Vista Business to Windows 7 Professional<br /> * Windows Vista Ultimate to Windows 7 Ultimate<br /><br />If you are performing an upgrade installation from Windows Vista, the base language must match the target Windows 7 language, you must have about 9GB of free space for the installation, and the installation can only occur on the same partition that holds Windows Vista. Existing applications and user data will be automatically migrated to the new Windows 7 installation.<br /><br />Clean installs will require about 16GB for the installation process. Unless the user chooses to repartition or format the current partition, Vista's files from C:\WINDOWS will be preserved under C:\WINDOWS.OLD, just as when upgrading from XP to Vista. Clean installs will also have to be performed when upgrading from a 32-bit version to a 64-bit version.<br />Windows Anytime Upgrade (WAU)<br /><br />Once you have some edition of Windows 7 on your system, whether you purchased it via an OEM or just upgraded from Windows XP or Windows Vista, you will be able to upgrade to a "more premium" version of Windows 7 by purchasing an upgrade key to unlock additional features, just as in with Vista. For example, you could start off with Windows Vista Home Premium, upgrade to Windows 7 Home Premium, and then later choose to upgrade to Windows 7 Professional.<br /><br />As with Vista, the same DVD includes the various editions. Unlike with Vista, every edition of Windows 7 is a superset of the previous edition, so you will not lose any features when upgrading.<br />Windows 7 for free and Ultimate Extras<br /><br />Some users have argued that Microsoft should release Windows 7 for free to everyone, while others suggest that only Windows Vista users should get Windows 7 for free. Finally, a third group says that Windows 7 should be the final Ultimate Extra that Microsoft gives out to Windows Vista Ultimate users. All three are unlikely scenarios, though I do have something to say about the last one.<br /><br />Last week, Microsoft noted that there would be no Ultimate Extras in Windows 7 Ultimate. Currently, if you upgrade Vista Ultimate to the Windows 7 Ultimate beta, your Ultimate Extras disappear. When I asked Microsoft if this was the expected behavior, I only got an "it's still in beta" response. In terms of the fate of Ultimate Extras on Vista, a spokesman told me the software giant still hasn't decided whether Microsoft Tinker was going to be the last Ultimate Extra that the company releases.<br /><br />Assuming that Windows 7 will not end up an Ultimate Extra for Vista, the only way to get Windows 7 for free will be to buy a Vista computer after July 1. In other words, if you purchase a computer with Vista preloaded on it, from July 1, 2009 through January 31, 2010 (OEMs can choose to have an even shorter time frame within the one Microsoft gives), you will have the option to upgrade to Windows 7 for free when it becomes available.<br /><br />According to a draft of the Windows 7 Technical Guarantee Program that Tech ARP acquired, the January 31 date may still change, depending on when Windows 7 is released.<br /><br />As you can see, Microsoft is offering many options for moving to Windows 7 on the consumer side. But if the upgrade won't be free, what will it cost? There's still no word on pricing, but Microsoft is certainly aware of the state of the economy; let's hope the software giant doesn't lose its business sense at a time like this.Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-23376249054190327162010-01-06T02:12:00.000-08:002010-01-06T02:15:19.566-08:00Core Java Interview Questions with Answers<meta equiv="Content-Type" content="text/html; charset=utf-8"><meta name="ProgId" content="Word.Document"><meta name="Generator" content="Microsoft Word 12"><meta name="Originator" content="Microsoft Word 12"><link rel="File-List" href="file:///C:%5CDOCUME%7E1%5CADMINI%7E1%5CLOCALS%7E1%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_filelist.xml"><link rel="themeData" href="file:///C:%5CDOCUME%7E1%5CADMINI%7E1%5CLOCALS%7E1%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_themedata.thmx"><link rel="colorSchemeMapping" 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What is the purpose of the System class?</b></p> <p class="MsoNormal" style="">The purpose of the System class is to provide access to system resources. </p> <p class="MsoNormal" style=""><b>102. Which TextComponent method is used to set a TextComponent to the read-only state?</b></p> <p class="MsoNormal" style="">setEditable() </p> <p class="MsoNormal" style=""><b>103. How are the elements of a CardLayout organized?</b></p> <p class="MsoNormal" style="">The elements of a CardLayout are stacked, one on top of the other, like a deck of cards. </p> <p class="MsoNormal" style=""><b>104. Is &&= a valid Java operator?</b></p> <p class="MsoNormal" style="">No, it is not. </p> <p class="MsoNormal" style=""><b>105. Name the eight primitive Java types.</b></p> <p class="MsoNormal" style="">The eight primitive types are byte, char, short, int, long, float, double, and boolean. </p> <p class="MsoNormal" style=""><b>106. Which class should you use to obtain design information about an object?</b></p> <p class="MsoNormal" style="">The Class class is used to obtain information about an object's design. </p> <p class="MsoNormal" style=""><b>107. What is the relationship between clipping and repainting?</b></p> <p class="MsoNormal" style="">When a window is repainted by the AWT painting thread, it sets the clipping regions to the area of the window that requires repainting. </p> <p class="MsoNormal" style=""><b>108. Is "abc" a primitive value?</b></p> <p class="MsoNormal" style="">The String literal "abc" is not a primitive value. It is a String object. </p> <p class="MsoNormal" style=""><b>109. What is the relationship between an event-listener interface and an event-adapter class?</b></p> <p class="MsoNormal" style="">An event-listener interface defines the methods that must be implemented by an event handler for a particular kind of event. An event adapter provides a default implementation of an event-listener interface. </p> <p class="MsoNormal" style=""><b>110. What restrictions are placed on the values of each case of a switch statement?</b></p> <p class="MsoNormal" style="">During compilation, the values of each case of a switch statement must evaluate to a value that can be promoted to an int value. </p> <p class="MsoNormal" style=""><b>111. What modifiers may be used with an interface declaration?</b></p> <p class="MsoNormal" style="">An interface may be declared as public or abstract. </p> <p class="MsoNormal" style=""><b>112. Is a class a subclass of itself?</b></p> <p class="MsoNormal" style="">A class is a subclass of itself. </p> <p class="MsoNormal" style=""><b>113. What is the highest-level event class of the event-delegation model?</b></p> <p class="MsoNormal" style="">The java.util.EventObject class is the highest-level class in the event-delegation class hierarchy. </p> <p class="MsoNormal" style=""><b>114. What event results from the clicking of a button?</b></p> <p class="MsoNormal" style="">The ActionEvent event is generated as the result of the clicking of a button. </p> <p class="MsoNormal" style=""><b>115. How can a GUI component handle its own events?</b></p> <p class="MsoNormal" style="">A component can handle its own events by implementing the required event-listener interface and adding itself as its own event listener. </p> <p class="MsoNormal" style=""><b>116. What is the difference between a while statement and a do statement?</b></p> <p class="MsoNormal" style="">A while statement checks at the beginning of a loop to see whether the next loop iteration should occur. A do statement checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the body of a loop at least once. </p> <p class="MsoNormal" style=""><b>117. How are the elements of a GridBagLayout organized?</b></p> <p class="MsoNormal" style="">The elements of a GridBagLayout are organized according to a grid. However, the elements are of different sizes and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes. </p> <p class="MsoNormal" style=""><b>118. What advantage do Java's layout managers provide over traditional windowing systems?</b></p> <p class="MsoNormal" style="">Java uses layout managers to lay out components in a consistent manner across all windowing platforms. Since Java's layout managers aren't tied to absolute sizing and positioning, they are able to accomodate platform-specific differences among windowing systems. </p> <p class="MsoNormal" style=""><b>119. What is the Collection interface?</b></p> <p class="MsoNormal" style="">The Collection interface provides support for the implementation of a mathematical bag - an unordered collection of objects that may contain duplicates. </p> <p class="MsoNormal" style=""><b>120. What modifiers can be used with a local inner class?</b></p> <p class="MsoNormal" style="">A local inner class may be final or abstract. </p> <p class="MsoNormal" style=""><b>121. What is the difference between static and non-static variables?</b></p> <p class="MsoNormal" style="">A static variable is associated with the class as a whole rather than with specific instances of a class. Non-static variables take on unique values with each object instance. </p> <p class="MsoNormal" style=""><b>122. What is the difference between the paint() and repaint() methods?</b></p> <p class="MsoNormal" style="">The paint() method supports painting via a Graphics object. The repaint() method is used to cause paint() to be invoked by the AWT painting thread. </p> <p class="MsoNormal" style=""><b>123. What is the purpose of the File class?</b></p> <p class="MsoNormal" style="">The File class is used to create objects that provide access to the files and directories of a local file system. </p> <p class="MsoNormal" style=""><b>124. Can an exception be rethrown?</b></p> <p class="MsoNormal" style="">Yes, an exception can be rethrown. </p> <p class="MsoNormal" style=""><b>125. Which Math method is used to calculate the absolute value of a number?</b></p> <p class="MsoNormal" style="">The abs() method is used to calculate absolute values. </p> <p class="MsoNormal" style=""><b>126. How does multithreading take place on a computer with a single CPU?</b></p> <p class="MsoNormal" style="">The operating system's task scheduler allocates execution time to multiple tasks. By quickly switching between executing tasks, it creates the impression that tasks execute sequentially. </p> <p class="MsoNormal" style=""><b>127. When does the compiler supply a default constructor for a class?</b></p> <p class="MsoNormal" style="">The compiler supplies a default constructor for a class if no other constructors are provided. </p> <p class="MsoNormal" style=""><b>128. When is the finally clause of a try-catch-finally statement executed?</b></p> <p class="MsoNormal" style="">The finally clause of the try-catch-finally statement is always executed unless the thread of execution terminates or an exception occurs within the execution of the finally clause. </p> <p class="MsoNormal" style=""><b>129. Which class is the immediate superclass of the Container class?</b></p> <p class="MsoNormal" style="">Component </p> <p class="MsoNormal" style=""><b>130. If a method is declared as protected, where may the method be accessed?</b></p> <p class="MsoNormal" style="">A protected method may only be accessed by classes or interfaces of the same package or by subclasses of the class in which it is declared. </p> <p class="MsoNormal" style=""><b>131. How can the Checkbox class be used to create a radio button?</b></p> <p class="MsoNormal" style="">By associating Checkbox objects with a CheckboxGroup. </p> <p class="MsoNormal" style=""><b>132. Which non-Unicode letter characters may be used as the first character of an identifier?</b></p> <p class="MsoNormal" style="">The non-Unicode letter characters $ and _ may appear as the first character of an identifier </p> <p class="MsoNormal" style=""><b>133. What restrictions are placed on method overloading?</b></p> <p class="MsoNormal" style="">Two methods may not have the same name and argument list but different return types. </p> <p class="MsoNormal" style=""><b>134. What happens when you invoke a thread's interrupt method while it is sleeping or waiting?</b></p> <p class="MsoNormal" style="">When a task's interrupt() method is executed, the task enters the ready state. The next time the task enters the running state, an InterruptedException is thrown. </p> <p class="MsoNormal" style=""><b>135. What is casting?</b></p> <p class="MsoNormal" style="">There are two types of casting, casting between primitive numeric types and casting between object references. Casting between numeric types is used to convert larger values, such as double values, to smaller values, such as byte values. Casting between object references is used to refer to an object by a compatible class, interface, or array type reference. </p> <p class="MsoNormal" style=""><b>136. What is the return type of a program's main() method?</b></p> <p class="MsoNormal" style="">A program's main() method has a void return type. </p> <p class="MsoNormal" style=""><b>137. Name four Container classes.</b></p> <p class="MsoNormal" style="">Window, Frame, Dialog, FileDialog, Panel, Applet, or ScrollPane </p> <p class="MsoNormal" style=""><b>138. What is the difference between a Choice and a List?</b></p> <p class="MsoNormal" style="">A Choice is displayed in a compact form that requires you to pull it down to see the list of available choices. Only one item may be selected from a Choice. A List may be displayed in such a way that several List items are visible. A List supports the selection of one or more List items. </p> <p class="MsoNormal" style=""><b>139. What class of exceptions are generated by the Java run-time system?</b></p> <p class="MsoNormal" style="">The Java runtime system generates RuntimeException and Error exceptions. </p> <p class="MsoNormal" style=""><b>140. What class allows you to read objects directly from a stream?</b></p> <p class="MsoNormal" style="">The ObjectInputStream class supports the reading of objects from input streams. </p> <p class="MsoNormal" style=""><b>141. What is the difference between a field variable and a local variable?</b></p> <p class="MsoNormal" style="">A field variable is a variable that is declared as a member of a class. A local variable is a variable that is declared local to a method. </p> <p class="MsoNormal" style=""><b>142. Under what conditions is an object's finalize() method invoked by the garbage collector?</b></p> <p class="MsoNormal" style="">The garbage collector invokes an object's finalize() method when it detects that the object has become unreachable. </p> <p class="MsoNormal" style=""><b>143. How are this() and super() used with constructors?</b></p> <p class="MsoNormal" style="">this() is used to invoke a constructor of the same class. super() is used to invoke a superclass constructor. </p> <p class="MsoNormal" style=""><b>144. What is the relationship between a method's throws clause and the exceptions that can be thrown during the method's execution?</b></p> <p class="MsoNormal" style="">A method's throws clause must declare any checked exceptions that are not caught within the body of the method. </p> <p class="MsoNormal" style=""><b>145. What is the difference between the JDK 1.02 event model and the event-delegation model introduced with JDK 1.1?</b></p> <p class="MsoNormal" style="">The JDK 1.02 event model uses an event inheritance or bubbling approach. In this model, components are required to handle their own events. If they do not handle a particular event, the event is inherited by (or bubbled up to) the component's container. The container then either handles the event or it is bubbled up to its container and so on, until the highest-level container has been tried. </p> <p class="MsoNormal" style="">In the event-delegation model, specific objects are designated as event handlers for GUI components. These objects implement event-listener interfaces. The event-delegation model is more efficient than the event-inheritance model because it eliminates the processing required to support the bubbling of unhandled events. </p> <p class="MsoNormal" style=""><b>146. How is it possible for two String objects with identical values not to be equal under the == operator?</b></p> <p class="MsoNormal" style="">The == operator compares two objects to determine if they are the same object in memory. It is possible for two String objects to have the same value, but located indifferent areas of memory. </p> <p class="MsoNormal" style=""><b>147. Why are the methods of the Math class static?</b></p> <p class="MsoNormal" style="">So they can be invoked as if they are a mathematical code library.<b> </b></p> <p class="MsoNormal" style=""><b>148. What Checkbox method allows you to tell if a Checkbox is checked?</b></p> <p class="MsoNormal" style="">getState() </p> <p class="MsoNormal" style=""><b>149. What state is a thread in when it is executing?</b></p> <p class="MsoNormal" style="">An executing thread is in the running state. </p> <p class="MsoNormal" style=""><b>150. What are the legal operands of the instanceof operator?</b></p> <p class="MsoNormal" style="">The left operand is an object reference or null value and the right operand is a class, interface, or array type. </p> <p class="MsoNormal" style=""><b>151. How are the elements of a GridLayout organized?</b></p> <p class="MsoNormal" style="">The elements of a GridBad layout are of equal size and are laid out using the squares of a grid. </p> <p class="MsoNormal" style=""><b>152. What an I/O filter?</b></p> <p class="MsoNormal" style="">An I/O filter is an object that reads from one stream and writes to another, usually altering the data in some way as it is passed from one stream to another. </p> <p class="MsoNormal" style=""><b>153. If an object is garbage collected, can it become reachable again?</b></p> <p class="MsoNormal" style="">Once an object is garbage collected, it ceases to exist. It can no longer become reachable again. </p> <p class="MsoNormal" style=""><b>154. What is the Set interface?</b></p> <p class="MsoNormal" style="">The Set interface provides methods for accessing the elements of a finite mathematical set. Sets do not allow duplicate elements.<b> </b></p> <p class="MsoNormal" style=""><b>155. What classes of exceptions may be thrown by a throw statement?</b></p> <p class="MsoNormal" style="">A throw statement may throw any expression that may be assigned to the Throwable type. </p> <p class="MsoNormal" style=""><b>156. What are E and PI?</b></p> <p class="MsoNormal" style="">E is the base of the natural logarithm and PI is mathematical value pi. </p> <p class="MsoNormal" style=""><b>157. Are true and false keywords?</b></p> <p class="MsoNormal" style="">The values true and false are not keywords. </p> <p class="MsoNormal" style=""><b>158. What is a void return type?</b></p> <p class="MsoNormal" style="">A void return type indicates that a method does not return a value. </p> <p class="MsoNormal" style=""><b>159. What is the purpose of the enableEvents() method?</b></p> <p class="MsoNormal" style="">The enableEvents() method is used to enable an event for a particular object. Normally, an event is enabled when a listener is added to an object for a particular event. The enableEvents() method is used by objects that handle events by overriding their event-dispatch methods. </p> <p class="MsoNormal" style=""><b>160. What is the difference between the File and RandomAccessFile classes?</b></p> <p class="MsoNormal" style="">The File class encapsulates the files and directories of the local file system. The RandomAccessFile class provides the methods needed to directly access data contained in any part of a file. </p> <p class="MsoNormal" style=""><b>161. What happens when you add a double value to a String?</b></p> <p class="MsoNormal" style="">The result is a String object. </p> <p class="MsoNormal" style=""><b>162. What is your platform's default character encoding?</b></p> <p class="MsoNormal" style="">If you are running Java on English Windows platforms, it is probably Cp1252. If you are running Java on English Solaris platforms, it is most likely 8859_1.. </p> <p class="MsoNormal" style=""><b>163. Which package is always imported by default?</b></p> <p class="MsoNormal" style="">The java.lang package is always imported by default. </p> <p class="MsoNormal" style=""><b>164. What interface must an object implement before it can be written to a stream as an object?</b></p> <p class="MsoNormal" style="">An object must implement the Serializable or Externalizable interface before it can be written to a stream as an object. </p> <p class="MsoNormal" style=""><b>165. How are this and super used?</b></p> <p class="MsoNormal" style="">this is used to refer to the current object instance. super is used to refer to the variables and methods of the superclass of the current object instance. </p> <p class="MsoNormal" style=""><b>166. What is the purpose of garbage collection?</b></p> <p class="MsoNormal" style="">The purpose of garbage collection is to identify and discard objects that are no longer needed by a program so that their resources may be reclaimed and reused.<b> </b></p> <p class="MsoNormal" style=""><b>167. What is a compilation unit?</b></p> <p class="MsoNormal" style="">A compilation unit is a Java source code file. </p> <p class="MsoNormal" style=""><b>168. What interface is extended by AWT event listeners?</b></p> <p class="MsoNormal" style="">All AWT event listeners extend the java.util.EventListener interface. </p> <p class="MsoNormal" style=""><b>169. What restrictions are placed on method overriding?</b></p> <p class="MsoNormal" style="">Overridden methods must have the same name, argument list, and return type. The overriding method may not limit the access of the method it overrides. The overriding method may not throw any exceptions that may not be thrown by the overridden method. </p> <p class="MsoNormal" style=""><b>170. How can a dead thread be restarted?</b></p> <p class="MsoNormal" style="">A dead thread cannot be restarted. </p> <p class="MsoNormal" style=""><b>171. What happens if an exception is not caught?</b></p> <p class="MsoNormal" style="">An uncaught exception results in the uncaughtException() method of the thread's ThreadGroup being invoked, which eventually results in the termination of the program in which it is thrown. </p> <p class="MsoNormal" style=""><b>172. What is a layout manager?</b></p> <p class="MsoNormal" style="">A layout manager is an object that is used to organize components in a container. </p> <p class="MsoNormal" style=""><b>173. Which arithmetic operations can result in the throwing of an ArithmeticException?</b></p> <p class="MsoNormal" style="">Integer / and % can result in the throwing of an ArithmeticException. </p> <p class="MsoNormal" style=""><b>174. What are three ways in which a thread can enter the waiting state?</b></p> <p class="MsoNormal" style="">A thread can enter the waiting state by invoking its sleep() method, by blocking on I/O, by unsuccessfully attempting to acquire an object's lock, or by invoking an object's wait() method. It can also enter the waiting state by invoking its (deprecated) suspend() method. </p> <p class="MsoNormal" style=""><b>175. Can an abstract class be final?</b></p> <p class="MsoNormal" style="">An abstract class may not be declared as final. </p> <p class="MsoNormal" style=""><b>176. What is the ResourceBundle class?</b></p> <p class="MsoNormal" style="">The ResourceBundle class is used to store locale-specific resources that can be loaded by a program to tailor the program's appearance to the particular locale in which it is being run. </p> <p class="MsoNormal" style=""><b>177. What happens if a try-catch-finally statement does not have a catch clause to handle an exception that is thrown within the body of the try statement?</b></p> <p class="MsoNormal" style="">The exception propagates up to the next higher level try-catch statement (if any) or results in the program's termination.<b> </b></p> <p class="MsoNormal" style=""><b>178. What is numeric promotion?</b></p> <p class="MsoNormal" style="">Numeric promotion is the conversion of a smaller numeric type to a larger numeric type, so that integer and floating-point operations may take place. In numerical promotion, byte, char, and short values are converted to int </p> <p class="MsoNormal" style="">values. The int values are also converted to long values, if necessary. The long and float values are converted to double values, as required. </p> <p class="MsoNormal" style=""><b>179. What is the difference between a Scrollbar and a ScrollPane?</b></p> <p class="MsoNormal" style="">A Scrollbar is a Component, but not a Container. A ScrollPane is a Container. A ScrollPane handles its own events and performs its own scrolling. </p> <p class="MsoNormal" style=""><b>180. What is the difference between a public and a non-public class?</b></p> <p class="MsoNormal" style="">A public class may be accessed outside of its package. A non-public class may not be accessed outside of its package. </p> <p class="MsoNormal" style=""><b>181. To what value is a variable of the boolean type automatically initialized?</b></p> <p class="MsoNormal" style="">The default value of the boolean type is false. </p> <p class="MsoNormal" style=""><b>182. Can try statements be nested?</b></p> <p class="MsoNormal" style="">Try statements may be tested. </p> <p class="MsoNormal" style=""><b>183. What is the difference between the prefix and postfix forms of the ++ operator?</b></p> <p class="MsoNormal" style="">The prefix form performs the increment operation and returns the value of the increment operation. The postfix form returns the current value all of the expression and then performs the increment operation on that value. </p> <p class="MsoNormal" style=""><b>184. What is the purpose of a statement block?</b></p> <p class="MsoNormal" style="">A statement block is used to organize a sequence of statements as a single statement group. </p> <p class="MsoNormal" style=""><b>185. What is a Java package and how is it used?</b></p> <p class="MsoNormal" style="">A Java package is a naming context for classes and interfaces. A package is used to create a separate name space for groups of classes and interfaces. Packages are also used to organize related classes and interfaces into a single API unit and to control accessibility to these classes and interfaces. </p> <p class="MsoNormal" style=""><b>186. What modifiers may be used with a top-level class?</b></p> <p class="MsoNormal" style="">A top-level class may be public, abstract, or final. </p> <p class="MsoNormal" style=""><b>187. What are the Object and Class classes used for?</b></p> <p class="MsoNormal" style="">The Object class is the highest-level class in the Java class hierarchy. The Class class is used to represent the classes and interfaces that are loaded by a Java program. </p> <p class="MsoNormal" style=""><b>188. How does a try statement determine which catch clause should be used to handle an exception?</b></p> <p class="MsoNormal" style="">When an exception is thrown within the body of a try statement, the catch clauses of the try statement are examined in the order in which they appear. The first catch clause that is capable of handling the exception is executed. The remaining catch clauses are ignored. </p> <p class="MsoNormal" style=""><b>189. Can an unreachable object become reachable again?</b></p> <p class="MsoNormal" style="">An unreachable object may become reachable again. This can happen when the object's finalize() method is invoked and the object performs an operation which causes it to become accessible to reachable objects. </p> <p class="MsoNormal" style=""><b>190. When is an object subject to garbage collection?</b></p> <p class="MsoNormal" style="">An object is subject to garbage collection when it becomes unreachable to the program in which it is used. </p> Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-14870948185731428852010-01-06T02:08:00.000-08:002010-01-06T02:11:44.987-08:00Core Java Interview Questions with Answers<meta equiv="Content-Type" content="text/html; charset=utf-8"><meta name="ProgId" content="Word.Document"><meta name="Generator" content="Microsoft Word 12"><meta name="Originator" content="Microsoft Word 12"><link rel="File-List" href="file:///C:%5CDOCUME%7E1%5CADMINI%7E1%5CLOCALS%7E1%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_filelist.xml"><link rel="themeData" href="file:///C:%5CDOCUME%7E1%5CADMINI%7E1%5CLOCALS%7E1%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_themedata.thmx"><link rel="colorSchemeMapping" 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What is the argument type of a program's main() method?</b></p> <p class="MsoNormal" style="">A program's main() method takes an argument of the String[] type. </p> <p class="MsoNormal" style=""><b>62. Which Java operator is right associative?</b></p> <p class="MsoNormal" style="">The = operator is right associative. </p> <p class="MsoNormal" style=""><b>63. What is the Locale class?</b></p> <p class="MsoNormal" style="">The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region. </p> <p class="MsoNormal" style=""><b>64. Can a double value be cast to a byte?</b></p> <p class="MsoNormal" style="">Yes, a double value can be cast to a byte. </p> <p class="MsoNormal" style=""><b>65. What is the difference between a break statement and a continue statement?</b></p> <p class="MsoNormal" style="">A break statement results in the termination of the statement to which it applies (switch, for, do, or while). A continue statement is used to end the current loop iteration and return control to the loop statement. </p> <p class="MsoNormal" style=""><b>66. What must a class do to implement an interface?</b></p> <p class="MsoNormal" style="">It must provide all of the methods in the interface and identify the interface in its implements clause. </p> <p class="MsoNormal" style=""><b>67. What method is invoked to cause an object to begin executing as a separate thread?</b></p> <p class="MsoNormal" style="">The start() method of the Thread class is invoked to cause an object to begin executing as a separate thread. </p> <p class="MsoNormal" style=""><b>68. Name two subclasses of the TextComponent class.</b></p> <p class="MsoNormal" style="">TextField and TextArea </p> <p class="MsoNormal" style=""><b>69. What is the advantage of the event-delegation model over the earlier event-inheritance model?</b></p> <p class="MsoNormal" style="">The event-delegation model has two advantages over the event-inheritance model. First, it enables event handling to be handled by objects other than the ones that generate the events (or their containers). This allows a clean separation between a component's design and its use. The other advantage of the event-delegation model is that it performs much better in applications where many events are generated. This performance improvement is due to the fact that the event-delegation model does not have to repeatedly process unhandled events, as is the case of the event-inheritance model. </p> <p class="MsoNormal" style=""><b>70. Which containers may have a MenuBar?</b></p> <p class="MsoNormal" style="">Frame<b> </b></p> <p class="MsoNormal" style=""><b>71. How are commas used in the intialization and iteration parts of a for statement?</b></p> <p class="MsoNormal" style="">Commas are used to separate multiple statements within the initialization and iteration parts of a for statement.<b> </b></p> <p class="MsoNormal" style=""><b>72. What is the purpose of the wait(), notify(), and notifyAll() methods?</b></p> <p class="MsoNormal" style="">The wait(),notify(), and notifyAll() methods are used to provide an efficient way for threads to wait for a shared resource. When a thread executes an object's wait() method, it enters the waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods. </p> <p class="MsoNormal" style=""><b>73. What is an abstract method?</b></p> <p class="MsoNormal" style="">An abstract method is a method whose implementation is deferred to a subclass. </p> <p class="MsoNormal" style=""><b>74. How are Java source code files named?</b></p> <p class="MsoNormal" style="">A Java source code file takes the name of a public class or interface that is defined within the file. A source code file may contain at most one public class or interface. If a public class or interface is defined within a source code file, then the source code file must take the name of the public class or interface. If no public class or interface is defined within a source code file, then the file must take on a name that is different than its classes and interfaces. Source code files use the .java extension. </p> <p class="MsoNormal" style=""><b>75. What is the relationship between the Canvas class and the Graphics class?</b></p> <p class="MsoNormal" style="">A Canvas object provides access to a Graphics object via its paint() method. </p> <p class="MsoNormal" style=""><b>76. What are the high-level thread states?</b></p> <p class="MsoNormal" style="">The high-level thread states are ready, running, waiting, and dead. </p> <p class="MsoNormal" style=""><b>77. What value does read() return when it has reached the end of a file?</b></p> <p class="MsoNormal" style="">The read() method returns -1 when it has reached the end of a file. </p> <p class="MsoNormal" style=""><b>78. Can a Byte object be cast to a double value?</b></p> <p class="MsoNormal" style="">No, an object cannot be cast to a primitive value. </p> <p class="MsoNormal" style=""><b>79. What is the difference between a static and a non-static inner class?</b></p> <p class="MsoNormal" style="">A non-static inner class may have object instances that are associated with instances of the class's outer class. A static inner class does not have any object instances. </p> <p class="MsoNormal" style=""><b>80. What is the difference between the String and StringBuffer classes?</b></p> <p class="MsoNormal" style="">String objects are constants. StringBuffer objects are not. </p> <p class="MsoNormal" style=""><b>81. If a variable is declared as private, where may the variable be accessed?</b></p> <p class="MsoNormal" style="">A private variable may only be accessed within the class in which it is declared.<b> </b></p> <p class="MsoNormal" style=""><b>82. What is an object's lock and which object's have locks?</b></p> <p class="MsoNormal" style="">An object's lock is a mechanism that is used by multiple threads to obtain synchronized access to the object. A thread may execute a synchronized method of an object only after it has acquired the object's lock. All objects and classes have locks. A class's lock is acquired on the class's Class object. </p> <p class="MsoNormal" style=""><b>83. What is the Dictionary class?</b></p> <p class="MsoNormal" style="">The Dictionary class provides the capability to store key-value pairs. </p> <p class="MsoNormal" style=""><b>84. How are the elements of a BorderLayout organized?</b></p> <p class="MsoNormal" style="">The elements of a BorderLayout are organized at the borders (North, South, East, and West) and the center of a container. </p> <p class="MsoNormal" style=""><b>85. What is the % operator?</b></p> <p class="MsoNormal" style="">It is referred to as the modulo or remainder operator. It returns the remainder of dividing the first operand by the second operand. </p> <p class="MsoNormal" style=""><b>86. When can an object reference be cast to an interface reference?</b></p> <p class="MsoNormal" style="">An object reference be cast to an interface reference when the object implements the referenced interface. </p> <p class="MsoNormal" style=""><b>87. What is the difference between a Window and a Frame?</b></p> <p class="MsoNormal" style="">The Frame class extends Window to define a main application window that can have a menu bar. </p> <p class="MsoNormal" style=""><b>88. Which class is extended by all other classes?</b></p> <p class="MsoNormal" style="">The Object class is extended by all other classes. </p> <p class="MsoNormal" style=""><b>89. Can an object be garbage collected while it is still reachable?</b></p> <p class="MsoNormal" style="">A reachable object cannot be garbage collected. Only unreachable objects may be garbage collected.. </p> <p class="MsoNormal" style=""><b>90. Is the ternary operator written x : y ? z or x ? y : z ?</b></p> <p class="MsoNormal" style="">It is written x ? y : z. </p> <p class="MsoNormal" style=""><b>91. What is the difference between the Font and FontMetrics classes?</b></p> <p class="MsoNormal" style="">The FontMetrics class is used to define implementation-specific properties, such as ascent and descent, of a Font object. </p> <p class="MsoNormal" style=""><b>92. How is rounding performed under integer division?</b></p> <p class="MsoNormal" style="">The fractional part of the result is truncated. This is known as rounding toward zero. </p> <p class="MsoNormal" style=""><b>93. What happens when a thread cannot acquire a lock on an object?</b></p> <p class="MsoNormal" style="">If a thread attempts to execute a synchronized method or synchronized statement and is unable to acquire an object's lock, it enters the waiting state until the lock becomes available. </p> <p class="MsoNormal" style=""><b>94. What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy?</b></p> <p class="MsoNormal" style="">The Reader/Writer class hierarchy is character-oriented, and the InputStream/OutputStream class hierarchy is byte-oriented. </p> <p class="MsoNormal" style=""><b>95. What classes of exceptions may be caught by a catch clause?</b></p> <p class="MsoNormal" style="">A catch clause can catch any exception that may be assigned to the Throwable type. This includes the Error and Exception types. </p> <p class="MsoNormal" style=""><b>96. If a class is declared without any access modifiers, where may the class be accessed?</b></p> <p class="MsoNormal" style="">A class that is declared without any access modifiers is said to have package access. This means that the class can only be accessed by other classes and interfaces that are defined within the same package. </p> <p class="MsoNormal" style=""><b>97. What is the SimpleTimeZone class?</b></p> <p class="MsoNormal" style="">The SimpleTimeZone class provides support for a Gregorian calendar. </p> <p class="MsoNormal" style=""><b>98. What is the Map interface?</b></p> <p class="MsoNormal" style="">The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.<b> </b></p> <p class="MsoNormal" style=""><b>99. Does a class inherit the constructors of its superclass?</b></p> <p class="MsoNormal" style="">A class does not inherit constructors from any of its superclasses. </p> <p class="MsoNormal" style=""><b>100. For which statements does it make sense to use a label?</b></p> <p class="MsoNormal" style="">The only statements for which it makes sense to use a label are those statements that can enclose a break or continue statement. </p> Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0tag:blogger.com,1999:blog-8341219017039661017.post-33702325917832759612009-12-07T23:09:00.000-08:002009-12-07T23:11:46.595-08:00The difference between 64 and 32 bit processorsIn the future, the battle between 64 bit vs 32 bit processors will inevitably yield the 64 bit processor as the victor, but this transition is going to take some time.<br /><br />First, I’ll talk about the pure mathematics and structure of the processors that are involved here. I’ll keep this part short and sweet. <br /><br /><br />A bit is short for “binary digit.” It is basically how a computer stores and makes references to data, memory, etc. A bit can have a value of 1 or 0, that’s it. So binary code is streams of 1’s and 0’s, such as this random sequence 100100100111. These bits are also how your processor does calculations. By using 32 bits your processor can represent numbers from 0 to 4,294,967,295 while a 64-bit machine can represent numbers from 0 to 18,446,744,073,709,551,615. Obviously this means your computer can do math with larger numbers, and be more efficient with smaller numbers.<br /><br />Now see, that description wasn’t too bad, but the question is how does this affect you, the average PC owner? The largest benefit will go to academic institutions and private companies, where large calculations are being performed, huge databases are being accessed, and complex problems are being solved.<br /><br />Everyone that doesn’t fall into that category will see some benefit of using 64 bit processors over 32 bit processors, but not much in today’s marketplace. The AMD Athlon 64-bit processor is completely backward compatible, meaning you can currently use it with 32-bit operating systems and software programs. You will see some benefits by using this setup, but because the programs weren’t written to take advantage of the extra power, they won’t use much of it.<br /><br />The true benefits of this set up don’t come from the amount of bits, but by the improved structure of the 64 bit vs 32 bit processor's older structure. A 64-bit processor is made with more advanced silicon processes, have more transistors, and faster speeds. This is currently where the true benefit of switching to a 64-bit processor lays.<br /><br />As for 64-bit operating systems and software, many are in the works, but nothing is in final version. Microsoft has released a beta version of Windows XP that takes advantage of the 64 bit technology, but there are still issues. The problem is when you run 32-bit software programs in the environment of a 64-bit operating system. Many programs won’t work properly, such as Adobe Acrobat and Windows Media Player, for example. Another issue is RAM. You really need about 4 GB of RAM to take full advantage of the capabilities offered by a 64-bit processor, while most PC owners have less than 1 GB under their computer’s hood.<br /><br />So, the question now is should you buy a 64 bit processor now, or wait?<br /><br />Disadvantages:<br /><br />You’re currently not able to take full advantage of the technology because the software vendors haven’t made the switch from 32-bit to 64-bit processors.<br /><br /><br />Most AMD Athlon 64 bit processors are expensive, with prices sure to go down in the future.<br /><br />Advantages:<br /><br />Better performance out of a 32-bit operating system.<br /><br /><br />Probably the last processor you’ll have to buy for many years to come.Vijay Ganesh P Nhttp://www.blogger.com/profile/05843826517167805114noreply@blogger.com0