Простой генератор сложных паролей

Зимой публиковал генератор паролей на C++. Народ попросил сделать на C — получилось очень даже ничего. Этот даже пароли поинтересней делает. Залил на github.com.

Листинг pgen.c

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

char *gen_pw(unsigned int length)
{
    unsigned int i, j;
    /*
     * Random 0 to 99 integer value.
     * Need to sort big, small and special symbols in new password.
    */
    unsigned int nrand;
    /*
     * Number of small, big and special symbols in new password.
    */
    unsigned int ns_latin, ns_glatin, ns_esc;
    /*
     * New password/ Will be returned for this function.
    */
    char *pw;
    /*
     * Values of small latin symbols.
    */
    char s_latin[] = {
        'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'
    };
    /*
     * Values of big latin symbols.
    */
    char s_glatin[] = {
        'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'
    };
    /*
     * Values of special ANSI symbols.
    */
    char s_esc[] = {
        '!','@','#','$','%','^','&','*','(',')','-','=','+','.',',',':',';','"','?'
    };

    /*
     * Allocating memory for new password array.
    */
    pw = (char *) malloc (length * sizeof(char));

    ns_latin = length - rand() % (length + 1);
    ns_glatin = length - ns_latin - rand() % (length - ns_latin + 1);

    if (ns_glatin > 0)
        ns_esc = length - ns_latin - ns_glatin;
    else
        ns_esc = length - ns_latin;

    for (i = 0; i < length; i++) {
        nrand = rand() % 100;

        /*
         * Sorting a big, small and special symbols for new password.
         * You can to modify it, if you don\'t like this algorithm.
        */

        if (nrand > 50)
            pw[i] = s_latin[rand() % sizeof(s_latin)];
        else
            if (nrand > 20 && nrand <= 50)
                pw[i] = s_glatin[rand() % sizeof(s_glatin)];
            else
                pw[i] = s_esc[rand() % sizeof(s_esc)];
    }

    return pw;
}
int main(int argc, char **argv)
{
    srand(time(0));
    unsigned int length;
    char *pw;
    /*
     * If user entered empty value for first argument.
    */
    if (!argv[1]) {
        exit(1);
    }
    else
        /*
         * If password is too long or too short.
        */
        if (atoi(argv[1]) > 4096 || atoi(argv[1]) < 5) {
            printf("Incorrect password length value.\nEnter 5 to 4096 integer value.");
            exit(2);
        } else // All's ok
            length = atoi(argv[1]);
    /*
     * Generating new password and print it.
    */
    pw = gen_pw(length);
    printf("%s",pw);
    // exit
    return 0;
}