C Program to Check Whether a Number is Prime or Not

A positive integer which is only divisible by 1 and iself is known as prime number. For example: 13 is a prime number because it is only divisible by 1 and 13 but, 15 is not prime number because it is divisible by 1, 3, 5 and 15.

#include<stdio.h>

#include<conio.h>

void main( )

{

    int n,i,flg=0;

    printf("Enter a number: ");

    scanf("%d",&n);

    for(i=2;i<=n/2;i++)

    {

        if(n%i==0)

        {

            flg=1;
            break;

        }

    }

    if(flg==0)

        printf("%d is a prime number.",n);

    else

        printf("%d is not a prime number.",n);

    getch( );

}

C Program to Display Prime Numbers Between Two Intervals >>