Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site tulane.UUCP
Path: utzoo!watmath!clyde!bonnie!akgua!akgub!tulane!jfk
From: jfk@tulane.UUCP (John Kreuter)
Newsgroups: net.arch
Subject: Re: uninitialized data
Message-ID: <164@tulane.UUCP>
Date: Wed, 25-Sep-85 12:17:45 EDT
Article-I.D.: tulane.164
Posted: Wed Sep 25 12:17:45 1985
Date-Received: Sat, 28-Sep-85 06:57:58 EDT
References: <436@uvm-cs.UUCP>
Organization: Tulane University, Dept. of Computer Science
Lines: 23

> 
>   Laex Colvin asks about an architecture that traps on using uniniitialized
> data.  The CDC 6000 series architecture does sort of.  An option to the loader
> will cause all data locations to be filled with a bit pattern representing
> "indefinite" which the CPU will choke on.
> -- 
> 							Stephen J. Hartley
> USENET:	{decvax,ihnp4}!dartvax!uvm-gen!uvm-cs!hartley	University of Vermont
> CSNET:	hartley%uvm@csnet-relay				(802) 656-3330, 862-5323

This is an extremely high overhead way of checking for uninitialized data.
An alternative would be an architecture in which a small tag field identifies
the type of the data.  This would have the further advantage of allowing, say,
arithmetic operators to be overloaded as they are in high level languages.

See "Advances in Computer Architecture", by Glenford J. Meyers (John Wiley
and sons, 1978)

					John Kreuter
					Tulane University
					New Orleans
{decvax, ihnp4}!ulysses!tulane!jfk