




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
}

Flowchart of while loop in C


Example of the while loop in C language
Let's see the simple program of while loop that prints table of 1.

#include
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
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
400
450
500


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

#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
}













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