#include<stdio.h> int fact(int n) { if (n <= 1) return 1; else return n * fact(n-1); } int main(int argc, char **argv) { if (argc > 1) { int n = atoi(argv[1]); printf("The factorial of %d is %d\n", n, fact(n)); return 0; } else { puts("Please specify a number."); return -1; } }