Prime number program in c | Calculate given number is prime or Not | prime number

Hello Everyone..

Today we write a program in c , that how to calculate the given number is prime of not. Before start the code , we know about the prime number ( What is prime number ?)

Prime Number : Prime number is a number which divisible by 1 and own so we called the number is prime. The condition is number is greater than 1. or other words, A number is divisble by itself or 1 so called the prime number.

So now let's Start the code...

Logic 1

#include<stdio.h>

int main()
{
    int n;
    printf("Enter the number : ");
    scanf("%d", &n);
    int count = 0;
    if(n==1){
        count = 1;
    }
    for(int i=2; i<n; i++){
        if(n%i==0){
             count++;
        }
    }

    if(count==0){
       printf("%d is prime", n);
    }
    else{
       printf("%d is not prime", n);
    }
    return 0;

}

Output :

Enter the number : 7
7 is prime

Logic 2


#include<stdio.h>

int main()
{
    int n;
    printf("Enter the number : ");
    scanf("%d", &n);
    int count = 0;
    int flag = 0;
    if(n==1){
        flag = 1;
    }
    for(int i=2; i<=n/2; i++){
        if(n%i==0){
            flag = 1;
        }else{
            count++;
        }
    }
    
    if(flag==0){
        printf("%d is prime", n);
    }
    else{
        printf("%d is not prime", n);
    }

    return 0;
}

Output :

Enter the number : 1
1 is not prime