From:	makulik AT tf16 DOT mch DOT sni DOT de (Makulik.Guenther T 27528 R 91-811 WS tx24 )
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Volatile
Date:	8 Aug 1997 10:27:13 GMT
Organization:	Siemens Nixdorf Inc.
Lines:	20
Message-ID:	<5sesa1$9sl$1@horus.mch.sni.de>
References:	<199708061619 DOT AA241634394 AT typhoon DOT rose DOT hp DOT com> <5sbq8s$jjd AT freenet-news DOT carleton DOT ca>
NNTP-Posting-Host:	tmntn.mch.sni.de
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Paul Derbyshire (ao950 AT FreeNet DOT Carleton DOT CA) wrote:
: What the heck is a "semaphore"???

A semaphore is a logical construct for synchronizing two processes or threads. Most
of the time it is realized as a single byte of information a number of processes/threads
have access to under the following certain conditions:

1. If the semaphore byte contains the status information 'Free', it can be changed
   to status 'Lock'

2. If the semaphore byte contains status 'Lock', the accessing process has to wait 
   until the status changes to 'Free' before it can be locked again.

That's the basic concept. 

There are library functions under UNIX for handling of shared memory and semaphores, 
does any on know wether DJGPP supports these facilities??

cu
guenther

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