While loop in C programming language

In this tutorial, We will discuss While loop in C programming language.

Typically, in programming languages, looping statements are used to perform repetitive statements until a specific condition is met in a block of code.

C program having three basic looping statements

for loop in C
while loop in C
do-while loop in C

Here, we will learn about while loop in C.

While loop in C programming language — While loop in Python

The syntax of While loop in C

Syntax

while(Test_expression){

//statement(s);

}

flow diagram of while loop

How while loop works in C language:

While loop in C programming language is used to execute a block of statements repeatedly until a given condition returns false. It is similar to for loop in C.

Initially, The initialization statements execute only once. text expression is evaluated by while loop. If the test expression is true(Boolean expression makes only two output 1 or 0) flow of control enters inside the body to execute the code. Continuously, test expression is evaluated and executed until the test expression is false.

This process repeats until the test expression is false.

When the test expression is false. while loop stops the execution and flow of control immediately exits from the loop.

Example

program 1

Here, it is a simple example to display 1 to 10

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int a=1;//variable declaration
    //and initialization
    while(a<=10){//test expression
    printf("value of a :%d\n",a);
    //display statements
    a++;//increment statements
    }
    getch();
    return 0;
}

When the above code is compiled and executed, it produces the following result

value of a :1
value of a :2
value of a :3
value of a :4
value of a :5
value of a :6
value of a :7
value of a :8
value of a :9
value of a :10

the above program displays the positive numbers from 1 to 10 using while loop

Program 2

#include <stdio.h>
#include <stdlib.h>

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

When the above code is compiled and executed, it produces the following result:

Square number of between 1 to 100
1
4
9
16
25
36
49
64
81
100
End the program

The above program displays square numbers between 1 to 100 using while loop

Program 3

Find factorial using while loop in C language

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int num;
    long fact;
    printf("Enter the number for find factorials :");
    scanf("%d",&num);
    fact=1;
    while(num>0) //if num>0, loop is terminated
    {
        fact*=num;  //factorial=factorial*number
        --num;
    }
    printf("Factorial is := %ld", fact);
    getch();
    return 0;
}

When the above code is compiled and executed, it produces the following result:

Enter the number for find factorials: 6

Factorial is: 720

the above program calculates factorial of given numbers using the while loop

The infinite while loop in C

while(true){ //it is always true
printf("This loop would never end");
}

Program 1

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int i=5;
    while(i>=5){ //i value greater than initialized value
    printf("%d",i);
    i++;
    }
    return 0;
}

When the above code is compiled and executed, it produces the following result:

This loop would never end

While loop with an array in C language

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int arr[]={45,67,75,34,65,89};
    int i=0;
    while(i<=5){
    printf("%d\n",arr[i]);
    i++;
    }
    getch();
    return 0;
}

When the above code is compiled and executed, it produces the following result: