C Program to Print All Prime Numbers between 1 and 100

Problem Description

This simple C program prints all the prime numbers between 1 and 100. A Prime number is a natural number greater than 1 that is only divisible by either 1 or itself. All numbers other than prime numbers are known as composite numbers. There are infinitely many prime numbers, here is the list of first few prime numbers
2 3 5 7 11 13 17 19 23 29 31 37.... 
This C program illustrates the use of nested for loops. The outer for loop iterate from 2 to 100 while the inner loop check the number for prime condition.

C Program to Print All Prime Numbers between 1 and 100 - Source code

     
                
    /*C program to print all the prime numbers between 1 and 100*/

  #include<stdio.h>

int main()
{
    int number,j,flag;
    printf(" The prime numbers between 1 and 100 : \n");
    for(number=2;number<=100;number++)
    {
        flag=0;
        for(j=2;j<=number/2;j++)
        {
            if(number % j == 0){
            flag = 1;
            break;
            }
               }
        if(flag==0)
            printf("\n    %d ",number);
              }
    return 0;
   }
     
      

Program Output

 The prime numbers between 1 and 100 :

    2
    3
    5
    7
    11
    13
    17
    19
    23
    29
    31
    37
    41
    43
    47
    53
    59
    61
    67
    71
    73
    79
    83
    89
    97

Program Explanation

1. This C program uses nested for loops to find and print all the prime numbers between 1 and 100.

2. The outer loop iterate through 2 to 100, while the inner loop use the modulus operator to check whether the number in current iteration is prime or not. If a prime number is found, the variable flag is set to 1 and the inner loop is existed using the break statement.

3. Otherwise, if flag variable remains zero, the number in current iteration is displayed on the screen as prime number.