Question

Write the following in C:

2. An integer is said to be prime if it is divisible by only 1 and itself. Write a function called prime() that takes in one integer number, and returns 1 (true) if the number is prime and 0 (false) otherwise. Write a program to generate six random numbers between 1 to 100 and calls function prime() on each one to determine if it is prime or not.

Answer 1

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>

int isPrime(int num)
{
   int i;
   if (num <= 1) return 0;
   if (num % 2 == 0 && num > 2) return 0;
   for (i = 3; i <= sqrt(num); i += 2)
   {
      if (num % i == 0)
         return 0;
   }
   return 1;
}

int main()
{
    int n, i;
   srand(time(NULL));
    
    for(i = 0;i<6;i++){
       n = 1+rand()%100;
        if(isPrime(n)){
            printf("%d is prime\n",n);
        }
        else{
            printf("%d is not prime\n",n);
        }
   }
   return 0;
}