Am i missing something here: #include "primes.h" /*how to linkto main.c*/ int is_prime(int n) { int k; int limit; if (n == 2) return 1; if (n % 2 == 0) return 0; limit = n / 2; for (k = 3; k <= limit; k += 2) if (n % k == 0) return 0; return 1; } I do not think that this works. What I am trying tho do is prime number search up to a specific number input from keyboard. I have xphe, P4 3.0 512KMB, nvidia 6800. Using micro$oft visual 2005. The first row is the amount of primes you want to see: printf("%5d: ", i); How do I link is_prime() to main to display all prime numbers after the ":" I have looked at C++ programming website and was unable to locate answer. I have found prime number algorithm but it didn't work on my machine. "By the way I'm a newbe @ programming. Any help would greatly be appreciated Hmmmmmmmm........