200 digit integer... how?

I have a project that requires working with two hundred digit numbers. I am at a loss on how to do this. If someone could modify the source below I am sure I could implement it into my own project. Thanks.

-skeptik

/*

* factor.c -- Prompts user to enter an integer N. It prints out

* if it is a prime or not. If not, it prints out all of its

* proper factors.

*/

#include <stdio.h>

int main(void)

{

int n;

int lcv;

int flag; /* flag initially is 1 and becomes 0 if

we determine that n is not a prime */

printf("Enter value of N : ");

scanf("%d", &n);

for (lcv=2, flag=1; lcv <= (n / 2); lcv++) {

if ((n % lcv) == 0) {

if (flag)

printf("non-trivial factors of %d are:\n", n);

flag = 0;

printf("\t%d\n", lcv);

}

}

if (flag)

printf("%d is prime\n", n);

}