The Towers of Hanoi as a C program.

Dennis Ritchie

C is perhaps the most ubiquitous programming language. In his paper titled The Development of the C Language, Dennis Ritchie writes:

The C programming language was devised in the early 1970s as a system implementation language for the nascent Unix operating system. Derived from the type-less language BCPL, it evolved a type structure; created on a tiny machine as a tool to improve a meager programming environment, it has become one of the dominant languages of today.

The celebrated C Programming Book (K&R) has its own page.

/* * The Towers Of Hanoi * C * Copyright (C) 1998 Amit Singh. All Rights Reserved. * * Tested with, ah well ... :) */ #include <stdio.h> #include <stdlib.h> #include <limits.h> #define FROM 1 #define TO 3 #define USING 2 void dohanoi(int N, int from, int to, int using) { if (N > 0) { dohanoi(N-1, from, using, to); printf ("move %d --> %d\n", from, to); dohanoi(N-1, using, to, from); } } int main (int argc, char **argv) { long int N; if (argc != 2) { fprintf(stderr, "usage: %s N\n", argv[0]); exit(1); } N = strtol(argv[1], (char **)NULL, 10); /* a bit of error checking, LONG_XXX should be there in limits.h */ if (N == LONG_MIN || N == LONG_MAX || N <= 0) { fprintf(stderr, "illegal value for number of disks\n"); exit(2); } dohanoi(N, FROM, TO, USING); exit(0); }