Display All Prime Numbers Between 1 to N Using For Loop in C

Problem

Write a C program to display all the prime numbers between 1 and n is a value given by the user at run time.

Solution

C program to display all the prime numbers between 1 and n is a value given by the user at run time is explained below −

Algorithm

Given below is an algorithm to display all the prime numbers between 1 and n is a value given by the user at run time.

Step 1 − Read n value.

Step 2 − Initialize count = 0

Step 3 − for i = 2 to n

   a. for j = 1 to i
   b. if i % j = 0
   c. then increment count
   d. if count is equal to 2
   e. then print i value

Flowchart

A flowchart is given below to explain the algorithm for the C program to display all the prime numbers between 1 and n is a value given by the user at run time.

Example

Following is the C program to display all the prime numbers between 1 and n is a value given by the user at run time −

#include<stdio.h>
void main(){
   int i, num, n, count;
   printf("Enter the range: 
");
   scanf("%d", &n);
   printf("The prime numbers in between the range 1 to %d:",n);
   for(num = 1;num<=n;num++){
      count = 0;
      for(i=2;i<=num/2;i++){
         if(num%i==0){
            count++;
         break;
      }
   }
   if(count==0 && num!= 1)
      printf("%d ",num);
   }
}

Output

When the above program is executed, it produces the following result −

Enter the range:50
The prime numbers in between the range 1 to 50:
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47