while loop in C

While loop is also known as a pre-tested loop. In general, a while loop allows a part of the code to be executed multiple times depending upon a given boolean condition. It can be viewed as a repeating if statement. The while loop is mostly used in the case where the number of iterations is not known in advance.

Syntax of while loop in C language

The syntax of while loop in c language is given below:

snippet
while(condition){
//code to be executed
}

Flowchart of while loop in C

flowchart of c while loop

Example of the while loop in C language

Let's see the simple program of while loop that prints table of 1.

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

Output

Output
1 2 3 4 5 6 7 8 9 10

Program to print table for the given number using while loop in C

snippet
#include
int main(){  
int i=1,number=0,b=9;  
printf("Enter a number: ");  
scanf("%d",&number);  
while(i<=10){  
printf("%d \n",(number*i));  
i++;  
}  
return 0;
}

Output

Output
Enter a number: 50 50 100 150 200 250 300 350 400 450 500
Output
Enter a number: 100 100 200 300 400 500 600 700 800 900 1000

Properties of while loop

  • A conditional expression is used to check the condition. The statements defined inside the while loop will repeatedly execute until the given condition fails.
  • The condition will be true if it returns 0. The condition will be false if it returns any non-zero number.
  • In while loop, the condition expression is compulsory.
  • Running a while loop without a body is possible.
  • We can have more than one conditional expression in while loop.
  • If the loop body contains only one statement, then the braces are optional.

Example 1

snippet
#include<stdio.h>
void main ()
{
	int j = 1;
	while(j+=2,j<=10)
	{
		printf("%d ",j); 
	}
	printf("%d",j);
}

Output

Output
3 5 7 9 11

Example 2

snippet
#include<stdio.h>
void main ()
{
	while()
	{
		printf("hello Javatpoint"); 
	}
}

Output

Output
compile time error: while loop can't be empty

Example 3

snippet
#include<stdio.h>
void main ()
{
	int x = 10, y = 2;
	while(x+y-1)
	{
		printf("%d %d",x--,y--);
	}
}

Output

Output
infinite loop

Infinitive while loop in C

If the expression passed in while loop results in any non-zero value then the loop will run the infinite number of times.

snippet
while(1){
//statement
}
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