Rad factorial algorithm

factorial.c

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

int factorial(int n) {
    int ans[200];       // answer can have a max of 200 digits.
    int temp,   // <- carry
        m,      // <- ones place of the prod, to put in the array
        prod,   // product of the current digit
        i, j;   // some counters

    ans[0] = 1; // the first digit
    m = 1;      // digit counter
    temp = 0;
    for (i = 1; i <= n; i++) {
        for (j = 0; j < m; j++) {
            prod = (ans[j] * i) + temp; // the product per digit * digit
            ans[j] = prod % 10;         // the digit in j
            temp = prod / 10;           // the carry value
        }
        while (temp != 0) {             // the carry value on the array
            ans[m] = temp % 10;         // the digit to put in the array
            temp = temp / 10;           // new temp (if any)
            m++;                        // increment the digit counter
        }
    }
        for (i = m-1; i >= 0; i--){     // print the answer
            printf("%d", ans[i]);
        }
        printf("\n");
    return 0;
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("Error: please supply an integer on the command line.\n");
        printf("%s\n", strerror(1));
        return 1;
    } else {
        factorial(atoi(argv[1]));
    }
    return 0;
}