/*
 *  help - give program help
 */

#include        <stdio.h>

help(argv)
char** argv;
{
    fprintf(stderr, "%s: HELP:\n", argv[0]);
    fprintf(stderr, "\n");
    fprintf(stderr, "    xor - perform \"exclusive or\" on two files byte-at-a-time\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "    This program takes an input file and a key file and performs\n");
    fprintf(stderr, "    an \"exclusive or\" on them byte-at-a-time, and writes the result\n");
    fprintf(stderr, "    to standard output.  Optionally, a number of bytes may be skipped\n");
    fprintf(stderr, "    first in the key file.\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "    This operation can be used to both encrypt and decrypt plain text\n");
    fprintf(stderr, "    or other data using the \"one time pad\" method, which employs an\n");
    fprintf(stderr, "    extremely long key (longer than the plain text message) and is\n");
    fprintf(stderr, "    theoretically unbreakbale if the key is truly random.\n");
    fprintf(stderr, "\n");

    } /* end of help */