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From: gordon@osiris.cso.uiuc.edu (John Gordon)
Newsgroups: comp.lang.c
Subject: Re: I'm confused about this
Keywords: getpid(), srand
Message-ID: <1990Nov21.025459.22201@ux1.cso.uiuc.edu>
Date: 21 Nov 90 02:54:59 GMT
References: <3945@vela.acs.oakland.edu>
Sender: news@ux1.cso.uiuc.edu (News)
Organization: University of Illinois at Urbana
Lines: 19

jmwojtal@vela.acs.oakland.edu (Wojo) writes:

>I got this C program and this part I don't understand:

>int   getpid();
>long  now;

>now = time(&now) / rand();
>srand(getpid() + (int)((now >> 16) + now + time(&now)));

>What does "srand" do to be exact?  It doesn't bring a value back?
>"getpid()" is declared, but the function is not in the program.

	srand() "seeds" the random-number generator, enabling it to produce
numbers that are more random than if you hadn't seeded it.  
	getpid() gets the process' ID number.  This is usually a fairly
good choice for a random number.
	So, the random-number generator is seeded with another random number.
This ensures very random results.