Difference between while(1) and while(0) in C language

Both of these are while loops used in the C language. But there is a primary difference between while(1) and while(0) in C language. In this article, we will discuss the same in brief. The while loop is used in a majority of computer programming languages. It acts as a type of control flow statement that allows its users to execute the code properly and repeatedly on the basis of the available boolean condition. This boolean condition can be both true and false.

What is while(1)?

The while(1) acts as an infinite loop that runs continually until a break statement is explicitly issued. Also, interestingly, not just while(1) but every non-zero integer is capable of giving a similar effect like how the while(1) does. Thus, whether it is while(1), while(3), or while(-764), all of these would generate infinite loops only.

Syntax:

while(some non-zero integer) or while(1)

{

// loop starts running infinitely

}

The while(1) loop can be used simply in the client-server programs. Thus, in a program, the server would run in an infinite while loop while receiving the packets that the client sends.

But the usage of while(1) is not practically advisable. It is because this loop is capable of increasing the usage of the CPU and then blocking the actual code. Meaning, we can’t really come out of a while(1) loop unless someone manually closes that particular program. It is only advised to use the while(1) loop in the places where the condition always needs to be true.

Here is an illustration of the use of while(1) loop in a C program:

#include <stdio.h>

int main()

{

int a = 0;

while (1) {

printf(“%d\n”, ++a);

if (a == 5)

break; // Used when coming out of loop

}

return 0;

}

The output generated here would be:

What is while(0)?

It is just the opposite of the while(1) loop. The while(0) loop means that the condition available to us will always be false. The execution of the code will, thus, never really occur.

Syntax:

while(0)

{

// given loop would not run

}

Here is an illustration of the use of while(0) loop in a C program:

#include<stdio.h>

int main()

{

int a = 0, flag=0;

while ( 0 )

{

// The execution of this line will never occur

printf( “%d\n”, ++a );

flag++;

if (a == 5)

break;

}

if (flag==0)

printf (“The loop didn’t execute here!”);

return 0;

}

The output generated here would be:

The loop didn’t execute here!