1000 factorial

Well, someone wrote that they could write a program to do 1000! in one line of Haskell. I said that it would take less than 100 lines of C to do the same. I wrote the program, and it is less than 100 lines of C:

#include <stdio.h>
#include <string.h>

#define LENGTH 10000

int max (int a, int b) { return (a > b) ? a : b; }
int min (int a, int b) { return (b > a) ? a : b; }

int length (unsigned char * a)
 {
   int i;
   i = LENGTH - 1;
   while ((a[i] == 0) && (i >= 0)) i--;
   return i + 1;
 }

void add (unsigned char * a, unsigned char * b)
 {
   int i, c, C;
   c = min(max(length(a), length(b)) + 1, LENGTH);
   for (i = 0, C = 0; i < c; i++)
    {
      a[i] += b[i] + C;
      C = a[i] > 99;
      if (C) a[i] -= 100;
    }
 }

   unsigned char x [LENGTH], y [LENGTH];
void mul (unsigned char * a, unsigned char * b)
 {
   int i, j, c, d, C;
   memset(y, '\0', LENGTH);
   c = min(length(a) + length(b) + 1, LENGTH);
   d = length(b);
   for (i = 0; i < d; i++)
    {
      memset(x, '\0', LENGTH);
      for (j = 0, C = 0; (i + j) < c; j++)
       {
         x[i + j] = (a[j] * b[i] + C) % 100;
         C = (a[j] * b[i] + C) / 100;
       }
      add(y, x);
    }
   memcpy(a, y, LENGTH);
 }

void numset (unsigned char * a, unsigned long b)
 {
   int i;
   for (i = 0; i < LENGTH; i++)
    {
      a[i] = b % 100;
      b /= 100;
    }
 }

int tz (unsigned char * a)
 {
   int i;
   for (i = 0; i < LENGTH; i++) if (a[i] != 0) return 0;
   return 1;
 }

   unsigned char minus1 [LENGTH], prod [LENGTH];
void fact (unsigned char * a)
 {
   numset(prod, 1);
   while (!tz(a))
    {
      mul(prod, a);
      add(a, minus1);
    }
   memcpy(a, prod, LENGTH);
 }

   unsigned char arg_res [LENGTH];
int main (void)
 {
   unsigned long a;
   int i;
   memset (minus1, 99, LENGTH);
   printf("Input the number to take the factorial of: ");
   scanf("%lu", &a);
   numset(arg_res, a);
   fact(arg_res);
   i = LENGTH - 1;
   while (arg_res[i] == 0) i--;
   while (i >= 0)
    {
      printf("%02d", (int) arg_res[i]);
      i--;
    }
   putchar('\n');
   return 0;
 }

>>125
I bet you're one of those assholes who say that 5 miles per gallon ought to be good enough for anybody. Wasting electricity means wasting fossil fuels, and no amount of work will appreciably change the amount of fossil fuels available on Earth.