It is a little program that theoritically can find out factorial of any number. You have to just change the value of the variable 'DIGIT'.

GiantFactorial.c

/**
* Developer: Minhas Kamal
* Date: August-2013
* Comment: The program can find very big factorial result, and it can be changed by changing 'DIGIT' value.
**/

#include <stdio.h>

#define DIGIT 10000000      //change accordingly

int main()
{
    while(1)
    {
        short int a[DIGIT+1];
        int x, i;
        for(i=0; i<DIGIT+1; i++) a[i]=-1;

        printf("Enter your integer : ");
        scanf("%d", &x);
        if(x<1) break;

        int j;
        i=x;
        for(j=DIGIT; i>0; j--)
        {
            a[j]=i%10;
            i=i/10;
        }

        int k=0;
        for(i=x-1; i>0; i--)
        {
            for(j=DIGIT; a[j]>=0; j--)
            {
                k=(i*a[j])+k;
                a[j]=k%10;
                k=k/10;
            }

            a[j]=k%10;
            k=k/10;
            a[j-1]=k;

            for(k=0; a[k]<1; k++) a[k]=-1;
            k=0;
        }


        for(i=0; a[i]<1; i++);
        for(; i<DIGIT+1; i++) printf("%hd", a[i]);
        printf("\n\n");
    }

    return 0;
}

I was really amazed by sensing the power of a simple program like this. 😃