C Program to Display Prime Numbers Between Intervals Using Using Function

#include<stdio.h>

int check_prime(int num);

int main()
{
   int n1,n2,i,flag;
   printf("Enter two numbers(intervals): ");
   scanf("%d %d",&n1, &n2);
   printf("Prime numbers between %d and %d are: ", n1, n2);
   for(i=n1+1;i<n2;++i)
   {
      flag=check_prime(i);
      if(flag==0)
         printf("%d ",i);
   }
   return 0;
}

int check_prime(int num) /* User-defined function to check prime number*/
{
   int j,flag=0;
   for(j=2;j<=num/2;++j){
        if(num%j==0){
            flag=1;
            break;
        }
   }
   return flag;
}