Warnings: Type Mismatch, functions, parameters? Homework: Guidance, not answers.

Ok, in C anything nonzero evaluates to true, conversely 0 evaluates to false. So you could:

Code:

int main (void){
	
	int num;
	
	printf("Enter a Number to Test if it is Prime: ");
	scanf("%d",&num);

	if(is_prime(num))
		printf("%d is prime", num);
	else
		printf("%d is not prime", num);

	system("PAUSE");
	return(0);
} /* End of Main*/

Note that N is unused and you are calling is_prime twice for no good reason...

Code:

  Y = is_prime (num);
   N = is_prime (num);

   if (Y == 1)
   {
    printf("%d is a Prime Number\n", num);
    }
    else
    {
     printf("%d is NOT a Prime Number\n", num);
     }

You could have also done this...

Code:

if (is_prime ( num ))
  printf("%d is a prime number.\n\n", num);
else
  printf("%d is not a prime number.\n\n",num);

or maybe this...

Code:

printf ("%d is ",num);
if (!is_prime (num))
  printf("not ");
printf("a prime number\n\n");

In your is_prime function you could have done this...

Code:

int is_prime (int p_num)
{ int i;

  if ( ! (p_num & 1) )   // prime numbers are all odd numbers
    return 0;

 for(i = 3; i < p_num; i ++)  // no need to check 1 or 2
   if (p_num%i==0)
     return 0;
 return 1; }

There are always other ways of doing things...