Web | This Site

C++ Basics
C++ Object Oriented
C++ Advanced
C++ Useful References
C++ Useful Resources
Selected Reading
© 2011 TutorialsPoint.COM

| Home |  | References |  | Discussion Forums |  | About TP

# C++ if...else statement

An if statement can be followed by an optional else statement, which executes when the boolean expression is false.

## Syntax:

The syntax of an if...else statement in C++ is:

    if(boolean_expression)
    {
       // statement(s) will execute if the boolean expression is true
    }
    else
    {
      // statement(s) will execute if the boolean expression is false
    }

If the boolean expression evaluates to true then the if block of code will be executed otherwise else block of code will be executed.

## Flow Diagram:

## Example:

    #include <iostream>
    using namespace std;

    int main ()
    {
       // local variable declaration:
       int a = 100;

       // check the boolean condition
       if( a < 20 )
       {
           // if condition is true then print the following
           cout << "a is less than 20;" << endl;
       }
       else
       {
           // if condition is false then print the following
           cout << "a is not less than 20;" << endl;
       }
       cout << "value of a is : " << a << endl;

       return 0;
    }

When the above code is compiled and executed, it produces following result:

    a is not less than 20;
    value of a is : 100

# The if...else if...else Statement:

An if statement can be followed by an optional else if...else statement, which is very usefull to test various conditions using single if...else if statement.

When using if , else if , else statements there are few points to keep in mind.

- An if can have zero or one else's and it must come after any else if's.

- An if can have zero to many else if's and they must come before the else.

- Once an else if succeeds, none of he remaining else if's or else's will be tested.

## Syntax:

The syntax of an if...else if...else statement in C++ is:

    if(boolean_expression 1)
    {
       // Executes when the boolean expression 1 is true
    }
    else if( boolean_expression 2)
    {
       // Executes when the boolean expression 2 is true
    }
    else if( boolean_expression 3)
    {
       // Executes when the boolean expression 3 is true
    }
    else
    {
       // executes when the none of the above condition is true.
    }

## Example:

    #include <iostream>
    using namespace std;

    int main ()
    {
       // local variable declaration:
       int a = 100;

       // check the boolean condition
       if( a == 10 )
       {
           // if condition is true then print the following
           cout << "Value of a is 10" << endl;
       }
       else if( a == 20 )
       {
           // if else if condition is true
           cout << "Value of a is 20" << endl;
       }
       else if( a == 30 )
       {
           // if else if condition is true
           cout << "Value of a is 30" << endl;
       }
       else
       {
           // if none of the conditions is true
           cout << "Value of a is not matching" << endl;
       }
       cout << "Exact value of a is : " << a << endl;

       return 0;
    }

When the above code is compiled and executed, it produces following result:

    Value of a is not matching
    Exact value of a is : 100

Advertisement

Online Image Processing

Indian Baby Names