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:

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

Example of the while loop in C language

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

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

Output

1 

2 

3 

4 

5 

6 

7 

8 

9 

10

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

#include<stdio.h>
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

Enter a number: 50 

50 

100 

150 

200 

250 

300 

350 

450 

500

Enter a number: 100 

100 

200 

300 

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

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

Output

3 5 7 9 11

Example 2

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

Output

compile time error: while loop can't be empty

Example 3

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

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.

while(1){
//statement
}