While loop in C

• The loop body in the while loop executes as long as the test expression is true.
• It is also an entry controlled loop.

Syntax

      while (Test Expression){
            loop-body ;
            Updation expression;
      }

Description

• The working of while loop is the same as that of for loop.
• Here initialization expression will be placed before the while statement.
• Then evaluate test expression.
• If it is true loop body and updating expression are executes.
• This process will continue until the test expression becomes false.
• Here the updating expression is placed within the body of the loop.

Example

PROGRAM TO DISPLAY NUMBERS FROM 1 TO 10 USING WHILE LOOP

      #include
      main()
      {
        int i;
        i=0;
        while(i<10){
            printf("%d",i);
            i+=1;
        }
      }

Output:  0 1 2 3 4 6 7 8 9

Working of program

• in the main function, the execution of the program starts
• First executes initialization expression,ie set i=0.
• Then evaluates condition expression i<10.ie 0<10 ,it is true, so jump to the body of the loop.
• in the body of the loop, it has given to print value of i.ie current value of i is 0, so print 0.
• next evaluate condition expession.here increment the value of i.ie i=i+1,ie i=0+1=1.
• Again evaluates condition expression i<10.ie 1<10 and loop body works.
• repeat steps 3,4,5,6 until the condition becomes false.
• when i=10, the condition expression will not satisfy. ie 10<10 is false.so exit from the loop.

Sample Programs

• C program to print numbers up to a given limit.
• C program to print even numbers up to a given limit.
• C program to print odd numbers up to a given limit.
• C program to find the sum of even numbers and sum of odd numbers up to a given limit.
• C program to print factorial of a number.
• C program to print the Fibonacci series up to a limit.
• C program to check whether a number is prime or not.
• C program to check whether a number is a palindrome or not.
• C program to find the sum of natural numbers up to a limit.