From: "John M. Aldrich" <fighteer AT cs DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: rand(), random()  !!!!!!!!!!!!!!!!!!!!!!!??????
Date: Thu, 02 Jul 1998 22:43:40 -0400
Organization: Two pounds of chaos and a pinch of salt.
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MalcolmJ7 wrote:
> 
> how do i randomize these functions?
> every time i use them they give me the same numbers, in the same order.
> when I use srandom() this, still gives me same numbers, in the same order.
> 
> isn't there a randomize() statement, like in turbo c?

When you use srandom() or srand(), you have to give them a value to use
as the seed.  If you give them the same value every time, they will of
course generate the same sequence of random numbers.  The most commonly
used RNG seed is the system clock, because it is guaranteed to be
different each time you run your program (within a granularity of 1
second or so).

Sample code:

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

int main( void )
{
    int i;

    srandom( (int) time( NULL ) );
    for ( i = 0; i < 100; i++ )
        printf( "%3d ", random() % 100 + 1 );
    printf( "\n" );
    return 0;
}

The srandom( (int) time( NULL ) ) statement is identical in meaning to
Turbo C's randomize().

FYI, srand() is used to seed rand(), and srandom() seeds random(). 
rand() and random() are completely independent of each other. 
(Documentation for srand() was omitted from the libc docs of v2.01 by
mistake.)

hth!

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