You can make the counter to 10 for making it find prime no.s upto ten digits!!:pleased: Code: #include <stdio.h> #include <math.h> #include <time.h> int is_prime(int number); int main(void) { int counter,limit; printf("Enter limit of prime numbers: "); scanf("%d",&limit); for (counter = 2; counter <= limit; counter++) { if (is_prime(counter)) printf("%d ", counter); } getch(); return 0; } int is_prime(int number) { int divisor; for (divisor = 2; divisor <= number / 2; divisor++) { if (number % divisor == 0) return 0; } return 1; }