WHILE Loop

Definition:

  • WHILE Loop is a decision-making control flow statement that execute body of statements based on given Boolean condition.
  • WHILE Loop belongs from Unbounded Loop category which means it will execute indefinite number of times.
  • WHILE Loop is known as Pre-Test Loop because condition is tested at first then executes the body of statements.
  • WHILE Loop is mostly used for the repetition of block of code as long as the condition is true.
  • WHILE Loop is also known as Entry-Controlled loop where condition is checked at the beginning itself.

Syntax:

The basic syntax of the WHILE Loop in C-Language

      while(condition)

                   {

                       // Body of statement(s)

                     // Increment or Decrement Operation

                   }

How WHILE Loop Works:

  1. The WHILE Loop check the condition inside the parenthesis ().
  2.  If the condition is true then body of WHILE Loop execute and again check the condition.
  3. This process will continue until the condition become false.
  4. If the condition is false then the WHILE Loop gets terminated.

Illustration of WHILE Loop

Program: Write a C program to print numbers from 1 to 5.

#include<stdio.h>

int main()

{

    int counter=1

while(counter<=5)

      {

          printf(“Value of counter: %d\n”, counter);

          counter++;

       }

return 0;

}

Output:

Value of counter: 1

Value of counter: 2

Value of counter: 3

Value of counter: 4

Value of counter: 5

Explanation:

    The initial value of counter=1

  1. When counter is 1 then WHILE Loop condition is true (counter<=5). Hence the body of WHILE Loop is executed and value of counter is increased to 2.
  2. Now counter is 2, WHILE Loop condition is true (counter<=5). Hence, again the body of WHILE Loop is executed and value of counter is increased to 3.
  3. This process will repeat until the WHILE Loop condition become false. (If counter is 6 then WHILE Loop condition counter<=5 become false)
  4. Once the WHILE Loop condition become false then loop gets terminated.

Application:

The concept of WHILE Loop is mostly used in such case where the number of iterations is not known in beginning or advance.

WHILE Loop is used in such situation where you want to print block of code repeatedly until the condition become false.