Data Structures Interview Questions Part 1

1. What is data structure?

A data structure is a way of organizing data that considers not only the items stored, but also their relationship to each other. Advance knowledge about the relationship between data items allows designing of efficient algorithms for the manipulation of data.

2. List out the areas in which data structures are applied extensively?

• Compiler Design
• Operating System,
• Database Management System
• Statistical analysis package,
• Numerical Analysis,
• Graphics,
• Artificial Intelligence,
• Simulation

3. What are the major data structures used in the following areas : RDBMS, Network data model & Hierarchical data model.

• RDBMS – Array (i.e. Array of structures)
• Network data model – Graph
• Hierarchical data model – Trees

4. What are the notations used in Evaluation of Arithmetic Expressions using prefix and postfix forms?

Polish and Reverse Polish notations.

5. What is the data structures used to perform recursion?

Stack. Because of its LIFO (Last In First Out) property it remembers its ‘caller’ so knows whom to return when the function has to return. Recursion makes use of system stack for storing the return addresses of the function calls.

Every recursive function has its equivalent iterative (non-recursive) function. Even when such equivalent iterative procedures are written, explicit stack is to be used.

6. If you are using C language to implement the heterogeneous linked list, what pointer type will you use?

The heterogeneous linked list contains different data types in its nodes and we need a link, pointer to connect them. It is not possible to use ordinary pointers for this. So we go for void pointer. Void pointer is capable of storing pointer to any type as it is a generic pointer type.

7. Minimum number of queues needed to implement the priority queue?

Two. One queue is used for actual storing of data and another for storing priorities.

Javascript DOM cheat sheet

Cheat sheet for Javascript Document Object Model(DOM)
DOM Methods
DOM Events
DOM Properties

JQuery Cheat Sheets

jQuery 1.1.3 Cheat Sheet

jQuery 1.3 Cheat Sheet

Zend Framework Cheat Sheet

• Zend_Controller
• Zend_Db/Zend_Db_Table
• Zend_Registry
• Zend_View/Zend_Layout

 

Embedded C Programmers Interview Questions Part 1

1. Using the #define statement, how would you declare a manifest constant that returns the number of seconds in a year? Disregard leap years in your answer.

#define SECONDS_PER_YEAR
(60 * 60 * 24 * 365)UL

2. Write the "standard" MIN macro-that is, a macro that takes two arguments and returns the smaller of the two arguments.

#define MIN(A,B)
((A)
<
= (B) ? (A) : (B))

3. Infinite loops often arise in embedded systems. How does you code an infinite loop in C?

There are several solutions to this question.

while(1)

{

}

Many programmers seem to prefer:

for(;;)

{

}

A third solution is to use a goto :

Loop:

goto Loop;

Candidates who propose this are either assembly language programmers (which is probably good), or else they are closet BASIC/FORTRAN programmers looking to get into a new field.

4. Using the variable a, give definitions for the following:

a) An integer

b) A pointer to an integer

c) A pointer to a pointer to an integer

d) An array of 10 integers

e) An array of 10 pointers to integers

f) A pointer to an array of 10 integers

g) A pointer to a function that takes an integer as an argument and returns an integer

h) An array of ten pointers to functions that take an integer argument and return an integer

a) int a; // An integer

b) int *a; // A pointer to an integer

c) int **a; // A pointer to a pointer to an integer

d) int a[10]; // An array of 10 integers

e) int *a[10]; // An array of 10 pointers to integers

f) int (*a)[10]; // A pointer to an array of 10 integers

g) int (*a)(int); // A pointer to a function a that takes an integer argument and returns an integer

h) int (*a[10])(int); // An array of 10 pointers to functions that take an integer argument and return an integer

5. What are the uses of the keyword static?

Static has three distinct uses in C:

• A variable declared static within the body of a function maintains its value between function invocations.
• A variable declared static within a module, (but outside the body of a function) is accessible by all functions within that module. It is not accessible by functions within any other module.
• Functions declared static within a module may only be called by other functions within that module. That is, the scope of the function is localized to the module within which it is declared.

6. What does the keyword volatile mean? Give three different examples of its use.

A volatile variable is one that can change unexpectedly. Consequently, the compiler can make no assumptions about the value of the variable. In particular, the optimizer must be careful to reload the variable every time it is used instead of holding a copy in a register. Examples of volatile variables are:

• Hardware registers in peripherals (for example, status registers)
• Non-automatic variables referenced within an interrupt service routine
• Variables shared by multiple tasks in a multi-threaded application

Java Interview Questions Part 15

1. What are the different scopes for Java variables?
The scope of a Java variable is determined by the context in which the variable is declared. Thus a java variable can have one of the three scopes at any given point in time. 

1. Instance : - These are typical object level variables, they are initialized to default values at the time of creation of object, and remain accessible as long as the object accessible.
2. Local : - These are the variables that are defined within a method. They remain accessbile only during the course of method excecution. When the method finishes execution, these variables fall out of scope.
3. Static: - These are the class level variables. They are initialized when the class is loaded in JVM for the first time and remain there as long as the class remains loaded. They are not tied to any particular object instance.

2. What is the default value of the local variables?
The local variables are not initialized to any default value, neither primitives nor object references. If you try to use these variables without initializing them explicitly, the java compiler will not compile the code. It will complain abt the local varaible not being initilized..

3. How many objects are created in the following piece of code?
MyClass c1, c2, c3;
c1 = new MyClass ();
c3 = new MyClass ();Only 2 objects are created, c1 and c3. The reference c2 is only declared and not initialized.

4. Can a public class MyClass be defined in a source file named YourClass.java?
No the source file name, if it contains a public class, must be the same as the public class name itself with a .java extension.

5. Can main method be declared final?
Yes, the main method can be declared final, in addition to being public static.

6. What will be the output of the following statement?
System.out.println ("1" + 3);
It will print 13.

7. What will be the default values of all the elements of an array defined as an instance variable?
If the array is an array of primitive types, then all the elements of the array will be initialized to the default value corresponding to that primitive type. e.g. All the elements of an array of int will be initialized to 0, while that of boolean type will be initialized to false. Whereas if the array is an array of references (of any type), all the elements will be initialized to null. 

Java Interview Questions Part 14

1. Is String a primitive data type in Java?
No String is not a primitive data type in Java, even though it is one of the most extensively used object. Strings in Java are instances of String class defined in java.lang package.

2. Is main a keyword in Java?
No, main is not a keyword in Java.

3. Is next a keyword in Java?
No, next is not a keyword.

4. Is delete a keyword in Java?
No, delete is not a keyword in Java. Java does not make use of explicit destructors the way C++ does.


5. Is exit a keyword in Java?
No. To exit a program explicitly you use exit method in System object.


6. What happens if you dont initialize an instance variable of any of the primitive types in Java?
Java by default initializes it to the default value for that primitive type. Thus an int will be initialized to 0, a boolean will be initialized to false.


7. What will be the initial value of an object reference which is defined as an instance variable?
The object references are all initialized to null in Java. However in order to do anything useful with these references, you must set them to a valid object, else you will get NullPointerExceptions everywhere you try to use such default initialized references.

Java Interview Questions Part 13

1. What modifiers are allowed for methods in an Interface?
Only public and abstract modifiers are allowed for methods in interfaces.

2. What are some alternatives to inheritance?
Delegation is an alternative to inheritance. Delegation means that you include an instance of another class as an instance variable, and forward messages to the instance. It is often safer than inheritance because it forces you to think about each message you forward, because the instance is of a known class, rather than a new class, and because it doesn't force you to accept all the methods of the super class: you can provide only the methods that really make sense. On the other hand, it makes you write more code, and it is harder to re-use (because it is not a subclass).

3. What does it mean that a method or field is "static"?
Static variables and methods are instantiated only once per class. In other words they are class variables, not instance variables. If you change the value of a static variable in a particular object, the value of that variable changes for all instances of that class. Static methods can be referenced with the name of the class rather than the name of a particular object of the class (though that works too). That's how library methods like System.out.println() work out is a static field in the java.lang.System class.

4. What is the difference between preemptive scheduling and time slicing?
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.

5. What is the catch or declare rule for method declarations?
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.

6. Is Empty .java file a valid source file?
Yes, an empty .java file is a perfectly valid source file.

7. Can a .java file contain more than one java classes?
Yes, a .java file contain more than one java classes, provided at the most one of them is a public class.

Java Interview Questions Part 12

1. Can applets communicate with each other?
At this point in time applets may communicate with other applets running in the same virtual machine. If the applets are of the same class, they can communicate via shared static variables. If the applets are of different classes, then each will need a reference to the same class with static variables. In any case the basic idea is to pass the information back and forth through a static variable. An applet can also get references to all other applets on the same page using the getApplets() method of java.applet.AppletContext. Once you get the reference to an applet, you can communicate with it by using its public members. It is conceivable to have applets in different virtual machines that talk to a server somewhere on the Internet and store any data that needs to be serialized there. Then, when another applet needs this data, it could connect to this same server. Implementing this is non-trivial.

2. What are the steps in the JDBC connection?
While making a JDBC connection we go through the following steps :
Step 1: Register the database driver by using :
Class.forName(\" driver classs for that specific database\" );
Step 2: Now create a database connection using :
Connection con = DriverManager.getConnection(url,username,password);
Step 3: Now Create a query using :
Statement stmt = Connection.Statement(\"select * from TABLE NAME\");
Step 4: Exceute the query :
stmt.exceuteUpdate();

3. How does a try statement determine which catch clause should be used to handle an exception?
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 exceptionis executed. The remaining catch clauses are ignored.

4. Can an unreachable object become reachable again?
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.

5. What method must be implemented by all threads?
All tasks must implement the run() method, whether they are a subclass of Thread or implement the Runnable interface.

6. What are synchronized methods and synchronized statements?
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.

7. What is Externalizable?
Externalizable is an Interface that extends Serializable Interface. And sends data into Streams in Compressed Format. It has two methods, writeExternal(ObjectOuput out) and readExternal(ObjectInput in)

Java Interview Questions Part 11

1. What is the purpose of finalization?
The purpose of finalization is to give an unreachable object the opportunity to perform any cleanup processing before the object is garbage collected.

2. What is the Locale class?
The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region.

3. What is the difference between a while statement and a do statement?
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.

4. What is the difference between static and non-static variables?
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.

5. How are this() and super() used with constructors?
this() is used to invoke a constructor of the same class. super() is used to invoke a superclass constructor.

6. What are synchronized methods and synchronized statements?
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.

7. What is daemon thread and which method is used to create the daemon thread?
Daemon thread is a low priority thread which runs intermittently in the back ground doing the garbage collection operation for the java runtime system. setDaemon method is used to create a daemon thread.

Java Interview Questions Part 10

1. If I write System.exit (0); at the end of the try block, will the finally block still execute?
No in this case the finally block will not execute because when you say System.exit (0); the control immediately goes out of the program, and thus finally never executes.

2. How are Observer and Observable used?
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.

3. What is synchronization and why is it important?
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 object while another thread is in the process of using or updating that object's value. This often leads to significant errors.

4. How does Java handle integer overflows and underflows?
It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.

5. Does garbage collection guarantee that a program will not run out of memory?
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.

6. What is the difference between preemptive scheduling and time slicing?
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.

7. When a thread is created and started, what is its initial state?
A thread is in the ready state after it has been created and started.

Java Interview Questions Part 9

1. If my class already extends from some other class what should I do if I want an instance of my class to be thrown as an exception object?
One can not do anytihng in this scenarion. Because Java does not allow multiple inheritance and does not provide any exception interface as well.

2. How does an exception permeate through the code?
An unhandled exception moves up the method stack in search of a matching When an exception is thrown from a code which is wrapped in a try block followed by one or more catch blocks, a search is made for matching catch block. If a matching type is found then that block will be invoked. If a matching type is not found then the exception moves up the method stack and reaches the caller method. Same procedure is repeated if the caller method is included in a try catch block. This process continues until a catch block handling the appropriate type of exception is found. If it does not find such a block then finally the program terminates.

3. What are the different ways to handle exceptions?
There are two ways to handle exceptions,

1. By wrapping the desired code in a try block followed by a catch block to catch the exceptions.
2. List the desired exceptions in the throws clause of the method and let the caller of the method hadle those exceptions.

4. What is the basic difference between the 2 approaches to exception handling.

• try catch block and
• specifying the candidate exceptions in the throws clause

5. When should you use which approach?
In the first approach as a programmer of the method, you urself are dealing with the exception. This is fine if you are in a best position to decide should be done in case of an exception. Whereas if it is not the responsibility of the method to deal with it's own exceptions, then do not use this approach. In this case use the second approach. In the second approach we are forcing the caller of the method to catch the exceptions, that the method is likely to throw. This is often the approach library creators use. They list the exception in the throws clause and we must catch them. You will find the same approach throughout the java libraries we use.

6. Is it necessary that each try block must be followed by a catch block?
It is not necessary that each try block must be followed by a catch block. It should be followed by either a catch block OR a finally block. And whatever exceptions are likely to be thrown should be declared in the throws clause of the method.

7. If I write return at the end of the try block, will the finally block still execute?
Yes even if you write return as the last statement in the try block and no exception occurs, the finally block will execute. The finally block will execute and then the control return.
 

Java Interview Questions Part 8

1. What are wrapper classes?
Java provides specialized classes corresponding to each of the primitive data types. These are called wrapper classes. They are e.g. Integer, Character, Double etc.

2. Why do we need wrapper classes?
It is sometimes easier to deal with primitives as objects. Moreover most of the collection classes store objects and not primitive data types. And also the wrapper classes provide many utility methods also. Because of these resons we need wrapper classes. And since we create instances of these classes we can store them in any of the collection classes and pass them around as a collection. Also we can pass them around as method parameters where a method expects an object.

3. What are checked exceptions?
Checked exception are those which the Java compiler forces you to catch. e.g. IOException are checked Exceptions.

4. What are runtime exceptions?
Runtime exceptions are those exceptions that are thrown at runtime because of either wrong input data or because of wrong business logic etc. These are not checked by the compiler at compile time.

5. What is the difference between error and an exception?
An error is an irrecoverable condition occurring at runtime. Such as OutOfMemory error. These JVM errors and you can not repair them at runtime. While exceptions are conditions that occur because of bad input etc. e.g. FileNotFoundException will be thrown if the specified file does not exist. Or a NullPointerException will take place if you try using a null reference. In most of the cases it is possible to recover from an exception (probably by giving user a feedback for entering proper values etc.).

6. How to create custom exceptions?
Your class should extend class Exception, or some more specific type thereof.

7. If I want an object of my class to be thrown as an exception object, what should I do?
The class should extend from Exception class. Or you can extend your class from some more precise exception type also. 

Java Interview Questions Part 7

1. What is the common usage of serialization?
Whenever an object is to be sent over the network, objects need to be serialized. Moreover if the state of an object is to be saved, objects need to be serilazed.

2. What is Externalizable interface?
Externalizable is an interface which contains two methods readExternal and writeExternal. These methods give you a control over the serialization mechanism. Thus if your class implements this interface, you can customize the serialization process by implementing these methods.

3. When you serialize an object, what happens to the object references included in the object?
The serialization mechanism generates an object graph for serialization. Thus it determines whether the included object references are serializable or not. This is a recursive process. Thus when an object is serialized, all the included objects are also serialized alongwith the original obect.

4. What one should take care of while serializing the object?
One should make sure that all the included objects are also serializable. If any of the objects is not serializable then it throws a NotSerializableException.

5. What happens to the static fields of a class during serialization?
There are three exceptions in which serialization doesnot necessarily read and write to the stream. 
These are

1. Serialization ignores static fields, because they are not part of ay particular state state.
2. Base class fields are only hendled if the base class itself is serializable.
3. Transient fields.

6. Does Java provide any construct to find out the size of an object?
No there is not sizeof operator in Java. So there is not direct way to determine the size of an object directly in Java.

7. Give a simplest way to find out the time a method takes for execution without using any profiling tool?
Read the system time just before the method is invoked and immediately after method returns. Take the time difference, which will give you the time taken by a method for execution.
To put it in code...
long start = System.currentTimeMillis ();
method ();
long end = System.currentTimeMillis ();
System.out.println ("Time taken for execution is " + (end - start));
Remember that if the time taken for execution is too small, it might show that it is taking zero milliseconds for execution. Try it on a method which is big enough, in the sense the one which is doing considerable amout of processing.

Java Interview Questions Part 6

1. What type of parameter passing does Java support?
In Java the arguments are always passed by value.

2. Primitive data types are passed by reference or pass by value?
Primitive data types are passed by value.

3. Objects are passed by value or by reference?
Java only supports pass by value. With objects, the object reference itself is passed by value and so both the original reference and parameter copy both refer to the same object. 

4. What is serialization?
Serialization is a mechanism by which you can save the state of an object by converting it to a byte stream.

5. How do I serialize an object to a file?
The class whose instances are to be serialized should implement an interface Serializable. Then you pass the instance to the ObjectOutputStream which is connected to a fileoutputstream. This will save the object to a file.

6. Which methods of Serializable interface should I implement?
The serializable interface is an empty interface, it does not contain any methods. So we do not implement any methods.

7. How can I customize the seralization process? i.e. how can one have a control over the serialization process?
Yes it is possible to have control over serialization process. The class should implement Externalizable interface. This interface contains two methods namely readExternal and writeExternal. You should implement these methods and write the logic for customizing the serialization process.

Java Interview Questions Part 5

1. What is Overriding?
When a class defines a method using the same name, return type, and arguments as a method in its superclass, the method in the class overrides the method in the superclass. When the method is invoked for an object of the class, it is the new definition of the method that is called, and not the method definition from superclass. Methods may be overridden to be more public, not more private.

2. What are different types of inner classes?
Nested top-level classes, Member classes, Local classes, Anonymous classes
Nested top-level classes- If you declare a class within a class and specify the static modifier, the compiler treats the class just like any other top-level class. Any class outside the declaring class accesses the nested class with the declaring class name acting similarly to a package. eg, outer.inner. Top-level inner classes implicitly have access only to static variables.There can also be inner interfaces. All of these are of the nested top-level variety.
Member classes - Member inner classes are just like other member methods and member variables and access to the member class is restricted, just like methods and variables. This means a public member class acts similarly to a nested top-level class. The primary difference between member classes and nested top-level classes is that member classes have access to the specific instance of the enclosing class.
Local classes - Local classes are like local variables, specific to a block of code. Their visibility is only within the block of their declaration. In order for the class to be useful beyond the declaration block, it would need to implement a more publicly available interface.Because local classes are not members, the modifiers public, protected, private, and static are not usable.
Anonymous classes - Anonymous inner classes extend local inner classes one level further. As anonymous classes have no name, you cannot provide a constructor.

3. Are the imports checked for validity at compile time? e.g. will the code containing an import such as java.lang.ABCD compile?
Yes the imports are checked for the semantic validity at compile time. The code containing above line of import will not compile. It will throw an error saying,can not resolve symbol
symbol : class ABCD
location: package io
import java.io.ABCD;

4. Does importing a package imports the subpackages as well? e.g. Does importing com.MyTest.* also import com.MyTest.UnitTests.*?
No you will have to import the subpackages explicitly. Importing com.MyTest.* will import classes in the package MyTest only. It will not import any class in any of it's subpackage.

5. What is the difference between declaring a variable and defining a variable?
In declaration we just mention the type of the variable and it's name. We do not initialize it. But defining means declaration + initialization.
e.g String s; is just a declaration while String s = new String ("abcd"); Or String s = "abcd"; are both definitions.

6. What is the default value of an object reference declared as an instance variable?
null unless we define it explicitly.

7. Can a top level class be private or protected?
No. A top level class can not be private or protected. It can have either "public" or no modifier. If it does not have a modifier it is supposed to have a default access.If a top level class is declared as private the compiler will complain that the "modifier private is not allowed here". This means that a top level class can not be private. Same is the case with protected.

Java Interview Questions Part 4

1. How can one prove that the array is not null but empty using one line of code?
Print args.length. It will print 0. That means it is empty. But if it would have been null then it would have thrown a NullPointerException on attempting to print args.length.

2. What environment variables do I need to set on my machine in order to be able to run Java programs?
CLASSPATH and PATH are the two variables.

3. Can an application have multiple classes having main method?
Yes it is possible. While starting the application we mention the class name to be run. The JVM will look for the Main method only in the class whose name you have mentioned. Hence there is not conflict amongst the multiple classes having main method.

4. Can I have multiple main methods in the same class?
No the program fails to compile. The compiler says that the main method is already defined in the class.

5. Do I need to import java.lang package any time? Why ?
No. It is by default loaded internally by the JVM.

6. Can I import same package/class twice? Will the JVM load the package twice at runtime?
One can import the same package or same class multiple times. Neither compiler nor JVM complains abt it. And the JVM will internally load the class only once no matter how many times you import the same class.

7. What are Checked and UnChecked Exception?
A checked exception is some subclass of Exception (or Exception itself), excluding class RuntimeException and its subclasses. Making an exception checked forces client programmers to deal with the possibility that the exception will be thrown. eg, IOException thrown by java.io.FileInputStream's read() method. Unchecked exceptions are RuntimeException and any of its subclasses. Class Error and its subclasses also are unchecked. With an unchecked exception, however, the compiler doesn't force client programmers either to catch the exception or declare it in a throws clause. In fact, client programmers may not even know that the exception could be thrown. eg, StringIndexOutOfBoundsException thrown by String's charAt() method. Checked exceptions must be caught at compile time. Runtime exceptions do not need to be. Errors often cannot be.

Java Interview Questions Part 3

1. What is final?
A final class can't be extended ie., final class may not be subclassed. A final method can't be overridden when its class is inherited. You can't change value of a final variable (is a constant).

2. What if the main method is declared as private?
The program compiles properly but at runtime it will give "Main method not public." message.

3. What if the static modifier is removed from the signature of the main method?
Program compiles. But at runtime throws an error "NoSuchMethodError".

4. What if I write static public void instead of public static void?
Program compiles and runs properly.

5. What if I do not provide the String array as the argument to the method?
Program compiles but throws a runtime error "NoSuchMethodError".

6. What is the first argument of the String array in main method?
The String array is empty. It does not have any element. This is unlike C/C++ where the first element by default is the program name.

7. If I do not provide any arguments on the command line, then the String array of Main method will be empty or null?
It is empty. But not null.

Java Interview Questions Part 2

1. Difference between Vector and ArrayList?
Vector is synchronized whereas arraylist is not.

2. Difference between Swing and Awt?
AWT are heavy-weight componenets. Swings are light-weight components. Hence swing works faster than AWT.

3. What is the difference between a constructor and a method?
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. 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.

4. What is an Iterator?
Some of the collection classes provide traversal of their contents via a java.util.Iterator interface. This interface allows you to walk through a collection of objects, operating on each object in turn. Remember when using Iterators that they contain a snapshot of the collection at the time the Iterator was obtained; generally it is not advisable to modify the collection itself while traversing an Iterator.

5. 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.
public: Public class is visible in other packages, field is visible everywhere (class must be public too)
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.
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.
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.

6. What is an abstract class?
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. A class may be declared abstract even if it has no abstract methods. This prevents it from being instantiated.

7. What is static in java?
Static means one per class, not one for each object no matter 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.

Java Interview Questions Part 1

1. What is the difference between an Interface and an Abstract class?
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.

2. What is the purpose of garbage collection in Java, and when is it used?
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.

3. Describe synchronization in respect to multithreading.
With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchonization, 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.

4. Explain different way of using thread?
The thread could be implemented by using runnable interface or by inheriting from the Thread class. The former is more advantageous, 'cause when you are going for multiple inheritance..the only interface can help.

5. What are pass by reference and passby value?
Pass By Reference means the passing the address itself rather than passing the value. Passby Value means passing a copy of the value to be passed.

6. What is HashMap and Map?
Map is Interface and Hashmap is class that implements that.

7. Difference between HashMap and HashTable?
The HashMap class is roughly equivalent to Hashtable, except that it is unsynchronized and permits nulls. (HashMap allows null values as key and value whereas Hashtable doesnt allow). HashMap does not guarantee that the order of the map will remain constant over time. HashMap is unsynchronized
and Hashtable is synchronized.

UNIX Commands Interview Questions Part 4

1. How to switch to a super user status to gain privileges?
Use 'su' command. The system asks for password and when valid entry is made the user gains super user (admin) privileges.

2. What are shell variables?
Shell variables are special variables, a name-value pair created and maintained by the shell.
Example: PATH, HOME, MAIL and TERM

3. What is redirection?
Directing the flow of data to the file or from the file for input or output.
Example : ls > wc

4. How to terminate a process which is running and the specialty on command kill 0?
With the help of kill command we can terminate the process.
Syntax: kill pid
Kill 0 - kills all processes in your system except the login shell.

5. What is a pipe and give an example?
A pipe is two or more commands separated by pipe char '|'. That tells the shell to arrange for the output of the preceding command to be passed as input to the following command.
Example : ls -l | pr
The output for a command ls is the standard input of pr.
When a sequence of commands are combined using pipe, then it is called pipeline.

6. Explain kill() and its possible return values.
There are four possible results from this call:
'kill()' returns 0. This implies that a process exists with the given PID, and the system would allow you to send signals to it. It is system-dependent whether the process could be a zombie.
'kill()' returns -1, 'errno == ESRCH' either no process exists with the given PID, or security enhancements are causing the system to deny its existence. (On some systems, the process could be a zombie.)
'kill()' returns -1, 'errno == EPERM' the system would not allow you to kill the specified process. This means that either the process exists (again, it could be a zombie) or draconian security enhancements are present
(e.g. your process is not allowed to send signals to *anybody*).
'kill()' returns -1, with some other value of 'errno' you are in trouble! The most-used technique is to assume that success or failure with 'EPERM' implies that the process exists, and any other error implies that it doesn't.
An alternative exists, if you are writing specifically for a system (or all those systems) that provide a '/proc'
filesystem: checking for the existence of '/proc/PID' may work.

7. What is relative path and absolute path.
Absolute path: Exact path from root directory.
Relative path: Relative to the current path.

UNIX Commands Interview Questions Part 3

1. Is it possible to restrict incoming message?
Yes, using the 'mesg' command.

2. What is the use of the command "ls -x chapter[1-5]"
ls stands for list; so it displays the list of the files that starts with 'chapter' with suffix '1' to '5', chapter1, chapter2, and so on.

3. Is 'du' a command? If so, what is its use?
Yes, it stands for 'disk usage'. With the help of this command you can find the disk capacity and free space of the disk.

4. Is it possible to count number char, line in a file; if so, How?
Yes, wc-stands for word count.
wc -c for counting number of characters in a file.
wc -l for counting lines in a file.

5. Name the data structure used to maintain file identification?
'inode', each file has a separate inode and a unique inode number.

6. How many prompts are available in a UNIX system?
Two prompts, PS1 (Primary Prompt), PS2 (Secondary Prompt).

7. How does the kernel differentiate device files and ordinary files?
Kernel checks 'type' field in the file's inode structure.

UNIX Commands Interview Questions Part 2

1. What is the use of 'grep' command?
'grep' is a pattern search command. It searches for the pattern, specified in the command line with appropriate option, in a file(s).
Syntax : grep
Example : grep 99mx mcafile

2. What is the difference between cat and more command?
Cat displays file contents. If the file is large the contents scroll off the screen before we view it. So command 'more' is like a pager which displays the contents page by page.

3. Write a command to kill the last background job?
Kill $!

4. Which command is used to delete all files in the current directory and all its sub-directories?
rm -r *

5. Write a command to display a file's contents in various formats?
$od -cbd file_name
c - character, b - binary (octal), d-decimal, od=Octal Dump.

6. What will the following command do?
$ echo *
It is similar to 'ls' command and displays all the files in the current directory.

7. Is it possible to create new a file system in UNIX?
Yes, 'mkfs' is used to create a new file system.

UNIX Commands Interview Questions Part 1

1. What is the significance of the "tee" command?
It reads the standard input and sends it to the standard output while redirecting a copy of what it has read to the file specified by the user.


2. What does the command " $who | sort –logfile > newfile" do?
The input from a pipe can be combined with the input from a file . The trick is to use the special symbol "-" (a hyphen) for those commands that recognize the hyphen as std input. In the above command the output from who becomes the std input to sort , meanwhile sort opens the file logfile, the contents of this file is sorted together with the output of who (rep by the hyphen) and the sorted output is redirected to the file newfile.

3. What does the command "$ls | wc –l > file1" do?
ls becomes the input to wc which counts the number of lines it receives as input and instead of displaying this count , the value is stored in file1.

4. Which of the following commands is not a filter man , (b) cat , (c) pg , (d) head
Ans: man
A filter is a program which can receive a flow of data from std input, process (or filter) it and send the result
to the std output.

5. How is the command "$cat file2 " different from "$cat >file2 and >> redirection operators ?
is the output redirection operator when used it overwrites while >> operator appends into the file.

6. Explain the steps that a shell follows while processing a command.
After the command line is terminated by the key, the shel goes ahead with processing the command line in one or more passes. The sequence is well defined and assumes the following order.
Parsing: The shell first breaks up the command line into words, using spaces and the delimiters, unless quoted. All consecutive occurrences of a space or tab are replaced here with a single space.
Variable evaluation: All words preceded by a $ are avaluated as variables, unless quoted or escaped.
Command substitution: Any command surrounded by backquotes is executed by the shell which then replaces the standard output of the command into the command line.
Wild-card interpretation: The shell finally scans the command line for wild-cards (the characters *, ?, [, ]). Any word containing a wild-card is replaced by a sorted list of filenames that match the pattern. The list of these filenames then forms the arguments to the command.
PATH evaluation: It finally looks for the PATH variable to determine the sequence of directories it has to search in order to hunt for the command.

7. What difference between cmp and diff commands?
cmp - Compares two files byte by byte and displays the first mismatch
diff - tells the changes to be made to make the files identical

PHP Interview Question Part 5

1. Name and explain five of the PHP error constants?

• E_ERROR: -This error is displayed when there is fatal error which halts the execution of the script immediately.
• E_WARNING: -This warns the programmer about the error but the execution of the script is not stopped.
• E_PARSE: -These errors occur during compile time and these errors should only be generated by the parser.
• E_USER_WARNING: -This warning error is generated by the user and is non fatal. This is set by the programmer using trigger_error().
• E_COMPILE_WARNING: -this error is generated by the Zend scripting engine. This is a compile time non fatal error.

PHP Interview Question Part 4

1. Describe about the security vulnerability of PHP?
According to the information obtained from the National vulnerability database, PHP has more than quarter of the software vulnerabilities discovered in 2008. Out of 33.33% software and scripts vulnerability PHP amounts to almost quarter of them. Register_globals a feature present in PHP is responsible for most of these vulnerabilities and now it is deprecated by PHP. Most of these security vulnerabilities occur due to poor programming techniques.
 
2. Explain about the data types in PHP?
PHP stores information numerical in a platform dependent range. Unsigned integers can be easily converted to signed integers. Decimal, octal, and hexadecimal notations can be easily assigned to integers. Floating point notation and two forms of scientific notation can be easily assigned to Real numbers. Zero is considered as false and all non zero numbers are considered as true.

3. What is a PHP accelerator?
PHP accelerator increases the speed of applications written in PHP. This boost of performance can be around 2-10 times. PHP accelerator increases the speed of the applications by decreasing parsing each and every time a PHP application runs. It depends upon factors such as time taken for execution of the PHP script and the actual percentage of the source code requested.
 
4. Explain about PHP cookies?
A Cookie is placed on the user desktop which uniquely identifies the user and every time a user views the webpage the same cookie is retrieved. With PHP a programmer can create and retrieve information simultaneously. The setcookie() function is used to create a cookie and PHP $_COOKIE variable helps the programmer to retrieve the cookie stored on the users computer. These both functions can function simultaneously.

5. Explain about Functions in PHP?
PHP has a large pool of functions and a huge number of them can be created by extensions. These functions can be defined at runtime by defining them inside the code. These functions have to be defined inside the parenthesis except for a class constructor function where there is no argument. Functions can be called or referenced by specifying their name.
 
6. Explain about objects in PHP?
In previous versions of PHP, object was fully copied before assigning a variable to a method. This problem was solved in new versions of PHP by the handle function. Many of the features present in PHP 5 are adopted from C++. Some of the features which are incorporated are restricted classes such as private and public, abstract and final classes, abstract and final methods, constructors and destructors with exception handling borrowed from C++.

7. Describe about PHP error and logging information?
Error handling function allows the user to detect the error and do necessary changes which paved the way for the error.
Logging functions pave the way for users to use log applications and send messages to system logs, email or for other specific purpose.
PHP has efficient error and logging constants to its credit. Some of them are E_ERROR, E_NOTICE, E_ALL, E_STRICT, etc.
 
 

ColdFusion Interview Question Part 4

1. How one can provide secured internet applications using adobe ColdFusion?

• Memory leak during transmit of information
• Impersonation which is like an exact clone which enters as legitimate
• Unauthorized access

These mechanisms are handled by adobe by using Data encryption, User Authentication and Access control.

2. Explain the structure of Cold fusion?
ColdFusion is implemented on the J2EE. J2EE is a standard, it is not a programming language. J2EE is an implementation of the Java programming language, but includes a number of Application Programming Interfaces (APIs) for connecting to databases, queuing messages, connecting to registries and naming and directory services.
All of these APIs are used by coldfusion for many of its base services and other runtime services.

ColdFusion consists of following components:

• cf script
• CFML
• ColdFusion Administrator
• Verity Search Server

3. What is CFCHART engine?
This CFCHART provides more than 200 different attributes which can be altered and these attributes can be used to control animation, labels, and colors. This CFCHART engine is used to produce high quality graphs, charts, sketches, and these charts can also aid you in Business analysis. These charts aid you very much in developing a good business presentation as you can control every part of it.
 
4. What are the benefits of multiple server instances?
The benefits of multiple server instances are, a single server is enough to deploy a host of applications which makes it highly applicable this was not the case when MX7 was present. Applications running on a server need not be stopped for maintenance as the work and load is shared upon multiple servers. Security, optimized applications and clustering are some of the main benefits of Adobe cold fusion multiple server instances.
 
5. What are the two primary types of files in a cold fusion application?
There are two primary types of file systems in ColdFusion which are used extensively they are Coldfusion templates and coldfusion pages. Developers in addition to these use CFML. These can contain HTML and often CFML for Dynamic content.
 
6. Can we modify ColdFusion server code and what are the two open source CFML parsing engines?
Server code of ColdFusion cannot be viewed or modified. The language of ColdFusion itself is documented and subjected to rights laid down by adobe. The two open source engines which are parsing ColdFusion’s markup languages are Blue dragon and Smith project. Blue dragon is a J2EE version.
 
7. What is Web Server?
A computer that delivers (serves up) Web pages. Every Web server has an IP address and possibly a domain name. For example, if you enter the URL http://www.domainname.com/index.html in your browser, this sends a request to the server whose domain name is domainname.com. The server then fetches the page named index.html and sends it to your browser.

Any computer can be turned into a Web server by installing server software and connecting the machine to the Internet. There are many Web server software applications, including public domain software from NCSA and Apache, and commercial packages from Microsoft, Netscape and others.
 

PHP Interview Question Part 3

1. Explain about switch statement in PHP?
Switch statement is executed line by line. PHP executes the statement only when the case statement matches the value of the switch expression. It does execute the statement until the end of the block till it finds the break statement. When the expression and statement matches themselves the code is executed.
 
2. Define about declare construct?
Declare construct allows you to define execution directives for a block set of code. This actually describes the way the code should perform. These declare construct can be set in such a manner that all the code is affected. The way the code performs can be set by the directive part which directly leads the code to follow.

3. Explain about looping in PHP?
Looping is used to run the same script many number of times. Following statements are used in PHP for looping while, do...while, for each, and for statement.
 
4. Explain about require and include function?
Include function collects all the text in a defined specific file and copies the text information to the file which has the include function in it
Require function is similar to the include function except that it handles the error system in a different manner. Require function displays a fatal error and stops the execution of the script while the include function still executes the script.

5. What is the alternative structure for control structures?
The basic control structures are if, for, while, do while, for each and switch. If you are planning to use alternative structures then the closing braces should be changed to endif, endfor, endwhile, endswitch, and endforeach. Similarly the opening brace of the alternative syntax should be changed to (:) or colon. The alternative structure is applicable to else and elseif also.

6. What are the different filter functions used to filter a variable?

• Filter_var()
• Filter_var_array()
• Filter_input
• Filter_input_array

7. Explain about PHP filter and why it should be used?
A PHP filter validates, filters according to the predefined statements from the programmer. It is very important for every programmer to validate user defines information as it can potential harm; PHP eliminated this risk by using PHP filter extension. This forms a good security practice for programmers.
 

ColdFusion Interview Question Part 3

1. What is cold fusion component roles implementation?
Cold fusion component roles implementation allows users to log into their role based administrator support function and not any other function. If a user tries to enter into other functions an error is thrown. These roles and components are taken by the Cold fusion. These roles and functions are transmitted through action script which allows the users to work on their components.
 
2. How can you create dynamic query?

• Dynamic SQL is a SQL code that your program generates using variables before the SQL is executed.
• In coldfusion, CFQUERY give full provision to write all conditional logic & looping to derive the dynamic sql statement to execute.
• You can use dynamic SQL to accomplish tasks such as adding WHERE clauses to a search based on the fields that the user filled out on a search criteria page.

3. State and explain about integrating Coldfusion applications with JSP.
A cold fusion page can contain JSP or a servlet and a JSP page can contain Coldfusion applications. This facilitates easy access to build hybrid functions and applications which can combine coldfusion components and servlets.

4. Explain about enterprise manager?
Enterprise manager helps you in admin functions. This will help you to create multiple cf server instances, through which you can experience advanced security, performance, and savings.

5. What are the different types of resources through which cold fusion can communicate?

• Mobile phones that support SMS
• XMPP or Lotus IM clients
• Java sockets
• Java messaging service
• Content management systems and file systems

6. What is Application Server?
A server that exposes business logic to client applications through various protocols including HTTP, HTTPS, IIOS/SSL. Eg: Sun Java Application server, weblogic server
It takes care of important issues like Transaction Management, Security, Database Connection Pooling, Clustering, Scalability,session management,load balancing,thread management and Messaging etc. A web server cannot provide these.
 
7. What is the benefit of extensible gateway architecture?
Developers can benefit from extensible gateways by limitless variety of emerging protocols. Developers can benefit by the creation of event gateways.
 

ColdFusion Interview Question Part 2

1. Explain about ColdFusion administrator?
ColdFusion administrator is a web based application just like the Cpanel this has many sub options through which you can control many functions such as data sources, global server settings, debugging settings, and application security settings. If you are having multiple administrator services then password must be provided for all those services. Also multiple user instances are provided where by a server can be split into cluster of Coldfusion administrators where a specific work can be provided to a specific individual who cannot alter changes.
 
2. What is CFAbort?

• Stops the processing of a ColdFusion page at the tag location.
• ColdFusion returns to the user or calling tag everything that was processed before the cfabort tag.
• You can optionally specify an error message to display using showError attribute. 
• The tag is often used with conditional logic to stop processing a page when a condition occurs.

3. What is SaveContent?

• Used to save the generated content to a variable, including the results of evaluating expressions and executing custom tags.
•  This tag requires an end tag.
• Main usage of savcontent is cache partial pages.

4. How can you connect with database from Coldfusion?

• Database manipulation tags (cfquery, cfstoredproc, cfinsert, cfupdate) have an attribute called datasource which used to identify/connect to a database.
• Data sources can be defined in CF administrator section.

5. What is Flash form?

• Flash form is a form like ordinary HTML form, with flash format which run on flash player enabled browsers.
• Using cfform tag CF automatically generates the swf format form's Flash binary from your CFML code.
• Flash Forms can be used to create a better forms experience for your users. 
• These features include accordion-style and multiple-tab form panes and automatic element positioning.
• You can also display cftree, cfgrid, and cfcalendar form elements as Flash

6. Describe about string encryption?
CFML language provides a 32 bit encryption which is symmetric key based. This function is called as Encrypt. Cold fusion at present uses 32 bit encryption but if your application requires 1024 bit encryption you can happily use that function because cold fusion integrates with third party libraries. Cold fusion also uses Hash function which is very important in safeguarding passwords. They use MD5 and XOR based algorithm.
 
7. Is it possible to write cold fusion in cold fusion?
No it is not possible to write ColdFusion in ColdFusion. Actually ColdFusion was written in Java and to write programs we need to implement other kinds of programs such as Java, .NET etc. These programs are required because ColdFusion alone cannot survive.  

ColdFusion Interview Question Part 1

1. What exactly is ColdFusion?
Cold fusion is the only software which helps the programmer to develop dynamic websites with backend database. ColdFusion is the only website which helps in developing dynamic websites. This is useful in software development. This has an application server and software development framework which greatly aid in developing computer software.
 
 2. What is CFFlush?
The first occurrence of this tag on a page sends back the HTML headers and any other available HTML. Subsequent cfflush tags on the page send only the output that was generated after the previous flush.
When you flush data, ensure that enough information is available, as some browsers might not respond if you flush only a small amount. Similarly, set the interval attribute for a few hundred bytes or more, but not thousands of bytes.
Use the interval attribute only when a large amount of output will be sent to the client, such as in a cfloop or a cfoutput of a large query. Using this form globally (such as in the Application.cfm file) might cause unexpected errors when CFML tags that modify HTML headers are executed.
 
3. Describe in detail about programming details in ColdFusion?
ColdFusion differs from major languages such as JSP, ASP.NET or PHP due to its associated scripting language and ColdFusion markup language. The syntax closely resembles to HTML. This language supports server side Action script and embedded scripts which can be written in ColdFusion script. This script is used for data driven websites. This technology also supports languages such as Flex which is used for client side scripting. This has many interfaces embedded in it which allows for services such as SMS and instant messaging.
 
4. What is the difference between HTMLEditFormat and HTMLCodeFormat?
Difference between HTMLCodeFormat function and HTMLEditFormat is that HTMLEditFormat does not surround the text in an HTML pre tag

5. What is CFQueryparam? What is the use?

• It separates parameters from the surrounding SQL.
• It allows the database’s SQL analyzer to more efficiently handle the SQL statement
• It validates data for the parameters which used to avoid SQL injection attacks.

6. Explain about some of the features present in ColdFusion MX7?
This edition from adobe was named as Macromedia ColdFusion MX7. Some of the features which are present are web forms, Xforms, adobe acrobat friendly report builder, flash, excel and rich text format style. This edition of cold fusion provided Gateways which helped in connecting various services such as IM, SMS, etc.
 
7. Describe about Clustering.
In previous installations of Adobe cold fusion multiple servers were required to run the application but adobe cold fusion 8 mitigated the problem by clustering Coldfusion into multiple physical installations which take over the load if any application fails during its course of time. This also allows in easy maintenance and possible reduction in maintaining multiple servers. This was made possible by J2EE server.
 
 

PHP Interview Question Part 1

1. What is PHP?

PHP stands for: PHP Hyper Text Preprocessor.

2. Why PHP?

PHP runs on different platforms (Windows, Linux, Unix, etc.).
PHP is compatible with almost all servers used today (Apache, IIS, etc.).
PHP is FREE to download from the official PHP resource: www.php.net.
PHP is easy to learn and runs efficiently on the server side.

3.What is a PHP File?

PHP files may contain text, HTML tags and scripts.
PHP files are returned to the browser as plain HTML.
PHP files have a file extension of  “.php”, “.php3?, or “.phtml”.

4. What is caching?

“Meta tags are easy to use, but aren’t very effective. That’s because they’re usually only honored by browser caches (which actually read the HTML), not proxy caches (which almost never read the HTML in the document).”

If a page is changed “nearly every day”, it will hardly be a problem in practical terms.

And in any case, it’s something to be handled at the server level, by making the server send some useful expiration information, using whatever needs to be done on a specific

server. Telling that a page expired twenty years ago is hardly a good idea if you can expect its lifetime to be a day or more, or at least several hours. Defeating proxy caching brutally wouldn’t be a good idea (and meta tags won’t do that, so the errors in a sense cancel out each other, so to say This has to be at the beginning of the file, with nothing before (e.g. no blank). This is a brute force variation, some adjustments are useful. (Server supporting PHP is recommended)Meta-tags wont work with proxies.

Proxies don’t work on the ‘HTML-layer’ but HTTP. Things depend on proxy settings also.”The Pragma header is generally ineffective because its meaning is not standardized and few caches honor it. Using <meta http-equiv=…> elements in HTML documents is also generally ineffective; some browsers may honor such markup, but other caches ignore it completely.” – Web Design Group That’s because the no-cache pragma is supposed to be part of a HTTP *request*. And *this* has been standardized since way back.

5. Are the PHP variable names case sensitive?
Yes. The php variable names cases sensitive. 

6. Are the PHP function names case sensitive?
No, Its not case sensitve functions.

7. What are the differences between PHP 3 and PHP 4?
Here’s a list of some of the more important new features:

• Extended API module.
• Generalized build process under Unix.
• Generic web server interface that also supports multi-threaded web servers
• Improved syntax highlighter.
• Native HTTP session support.
• Output buffering support.
• More powerful configuration system.
• Reference counting.

 

PHP Interview Question Part 2

1. What is the difference between echo and print statement?
There is a slight difference between print and echo which would depend on how you
want to use the outcome. Using the print method can return a true/false value. This may
be helpful during a script execution of somesort. Echo does not return a value, but has
been considered as a faster executed command. All this can get into a rather
complicated discussion, so for now, you can just use whichever one you prefer.

2.How to make a download page in own site, which i can know that how many file has
been loaded by particular user or particular ipaddress?
We can use hyperlink having URL where file are kept. and we only allow regisetered
user to download. from session of user we can get the user detail

3. What is the difference between mysql_connect and mysql_pconnect?
 mysql_pconnect establishes a persistent connection. If you don't need one (such as a
website that is mostly HTML files or PHP files that don't call the db) then you don't
need to use it. mysql_connect establishes a connection for the duration of the script
that access the db. Once the script has finished executing it closes the connection. The
Templateshut.com
only time you need to close the connection manually is if you jump out of the script for
any reason.
If you do use mysql_pconnect. You only need to call it once for the session. That's the
beauty of it. It will hold open a connection to the db that you can use over and over
again simply by calling the resource ID whenever you need to interact with the db.

4. How can I get IP Address?
We can use SERVER var $_SERVER['SERVER_ADDR'] and getenv("REMOTE_ADDR")
functions to get the IP address.

5. How we know the browser properties?
get_browser() attempts to determine the capabilities of the user's browser. This is done
by looking up the browser's information in the browscap.ini file.
echo $_SERVER['HTTP_USER_AGENT'] . "

6. What is the difference between require_once(), require(), include().
Difference between require() and require_once(): require() includes and evaluates a
specific file, while require_once() does that only if it has not been included before (on
the same page). So, require_once() is recommended to use when you want to include a
file where you have a lot of functions for example. This way you make sure you don't
include the file more times and you will not get the "function re-declared" error.
Difference between require() and include() is that require() produces a FATAL ERROR
if the file you want to include is not found, while include() only produces a WARNING.
There is also include_once() which is the same as include(), but the difference between
them is the same as the difference between require() and require_once().

7. What is CAPTCHA?
CAPTCHA stands for Completely Automated Public Turing Test to tell Computers and
Humans Apart. To prevent spammers from using bots to automatically fill out forms,
CAPTCHA programmers will generate an image containing distorted images of a string
of numbers and letters. Computers cannot determine what the numbers and letters are
from the image but humans have great pattern recognition abilities and will be able to
fairly accurately determine the string of numbers and letters. By entering the numbers
and letters from the image in the validation field, the application can be fairly assured
that there is a human client using it.

CSS Interview Question Part I

1. Explain in brief about the term CSS.
A stylesheet language used to describe the presentation of a document written in a markup language. Cascading Style Sheets are a big breakthrough in Web design because they allow developers to control the style and layout of multiple Web pages all at once.

2. What are the various style sheets?
Inline, external, imported and embedded are the different types of style sheets.

3. List various font attributes used in style sheet.

font-style
font-variant
font-weight
font-size/line-height
font-family
caption
icon
menu
message-box
small-caption
status-bar

4. Explain inline, embedded and external style sheets.

Inline
If only a small piece of code has to be styled then inline style sheets can be used.

Embedded
Embedded style sheets are put between the <head> </head> tags.

External
If you want to apply a style to all the pages within your website by changing just one style sheet, then external style sheets can be used.

5. Are Style Sheets case sensitive?

No. Style sheets are case insensitive. Whatever is case insensitive in HTML is also case insensitive in CSS. However, parts that are not under control of CSS like font family names and URLs can be case sensitive - IMAGE.gif and image.gif is not the same file.

6. What is selector?

CSS selector is equivalent of HTML element(s). It is a string identifying to which element(s) the corresponding declaration(s) will apply and as such the link between the HTML document and the style sheet.

For example in P {text-indent: 10pt} the selector is P and is called type selector as it matches all instances of this element type in the document.

in P, UL {text-indent: 10pt} the selector is P and UL (see grouping); in .class {text-indent: 10pt} the selector is .class (see class selector).

7. Can I include comments in my Style Sheet?

Yes. Comments can be written anywhere where whitespace is allowed and are treated as white space themselves. Anything written between /* and */ is treated as a comment (white space). NOTE: Comments cannot be nested.