While Loop in C Programming Language

Sometimes we need repeat an instruction a certain number of times, so we use the while loop in c programming language. At each execution of a cycle we call iteration.

While Loop Syntax

while(condition){
    <instruction>
}

 

Explained Condition:

  1. In while loop the condition is evaluated, if returns false the cycle ends, and continues one the closing of the while loop } .
  2. if the condition returns true, the cycle will executed and tested while the condition is true, and then, ends the cycle.

 

Example

#include <stdio.h>
int main(int argc, char** argv) {

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

    return (EXIT_SUCCESS);
}

 

Code Explained

  • line4, we declare the variable ‘‘ of type integer, and set the value to 1;
  • line6 and line9, we use the while loop and establish the condition ” i <= 10 “, that will be repeated 10 times;
  • line5, we print the variable ;
  • line6, we increment the value of variable in 1.
    • i++ it equal to i = i + 1

 

Output:

1
2
3
4
5
6
7
8
9
10

 

Examples of programs

Create all Math tables

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

int main(int argc, char** argv) {
    
    //we initialize the variables values to 1
    int i =1, j=1;
    
    //this is the external while that represents the math
    //tables 1,2,3,4,5,...
    while(i<=10){
        //we set again the value of variable j beacause after the first 
        //execution of the program variable j starts the second exectution with the value 10
        j =1;
        //this while represents the numbers that will be multiplied
        while(j<=10){
            //we print the all tables 
            // i * j, 1 * 3 = 3
            printf("%d * %d = %d\n",i, j, i*j);
            j++;
        }
        //we break the line between the tables
        printf("\n");
        //we add 1 to value i
        i++;
    }
            

    return (EXIT_SUCCESS);
}

Output

1 * 1 = 1
1 * 2 = 2
1 * 3 = 3
1 * 4 = 4
1 * 5 = 5
1 * 6 = 6
1 * 7 = 7
1 * 8 = 8
1 * 9 = 9
1 * 10 = 10

2 * 1 = 2
2 * 2 = 4
2 * 3 = 6
2 * 4 = 8
2 * 5 = 10
2 * 6 = 12
2 * 7 = 14
2 * 8 = 16
2 * 9 = 18
2 * 10 = 20

3 * 1 = 3
3 * 2 = 6
3 * 3 = 9
3 * 4 = 12
3 * 5 = 15
3 * 6 = 18
3 * 7 = 21
3 * 8 = 24
3 * 9 = 27
3 * 10 = 30

4 * 1 = 4
4 * 2 = 8
4 * 3 = 12
4 * 4 = 16
4 * 5 = 20
4 * 6 = 24
4 * 7 = 28
4 * 8 = 32
4 * 9 = 36
4 * 10 = 40

5 * 1 = 5
5 * 2 = 10
5 * 3 = 15
5 * 4 = 20
5 * 5 = 25
5 * 6 = 30
5 * 7 = 35
5 * 8 = 40
5 * 9 = 45
5 * 10 = 50

6 * 1 = 6
6 * 2 = 12
6 * 3 = 18
6 * 4 = 24
6 * 5 = 30
6 * 6 = 36
6 * 7 = 42
6 * 8 = 48
6 * 9 = 54
6 * 10 = 60

7 * 1 = 7
7 * 2 = 14
7 * 3 = 21
7 * 4 = 28
7 * 5 = 35
7 * 6 = 42
7 * 7 = 49
7 * 8 = 56
7 * 9 = 63
7 * 10 = 70

8 * 1 = 8
8 * 2 = 16
8 * 3 = 24
8 * 4 = 32
8 * 5 = 40
8 * 6 = 48
8 * 7 = 56
8 * 8 = 64
8 * 9 = 72
8 * 10 = 80

9 * 1 = 9
9 * 2 = 18
9 * 3 = 27
9 * 4 = 36
9 * 5 = 45
9 * 6 = 54
9 * 7 = 63
9 * 8 = 72
9 * 9 = 81
9 * 10 = 90

10 * 1 = 10
10 * 2 = 20
10 * 3 = 30
10 * 4 = 40
10 * 5 = 50
10 * 6 = 60
10 * 7 = 70
10 * 8 = 80
10 * 9 = 90
10 * 10 = 100


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