Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!cs.utexas.edu!sm.unisys.com!ism780c!news
From: news@ism780c.isc.com (News system)
Newsgroups: comp.arch
Subject: Re: Register Windows
Message-ID: <17929@ism780c.isc.com>
Date: 13 Oct 88 19:02:11 GMT
References: <46500028@uxe.cso.uiuc.edu> <2768@ima.ima.isc.com>
Reply-To: marv@ism780.UUCP (Marvin Rubenstein)
Distribution: na
Organization: Interactive Systems Corp., Santa Monica CA
Lines: 17

In article <2768@ima.ima.isc.com> johnl@ima.UUCP (John R. Levine) writes:
[definition of a register window]
>
>It's a little piece of Lexan in the chip package of a microprocessor that lets
>you see into the machine's registers. Writers of optimizing compilers find
>these windows invaluable for debugging and tuning object code.

Historical Note:
The first programmable digital computer that I worked with was a CPC (card
programed calculator).  This machine had 800 decimal digits of storage that
could be arranged into one or more registers via a patch panel.  The
implementation of the digits was mechanical, much like an automobile
odometer.  The value in a register could actually be seen (numbers painted on
wheels).  The primary debugging aid for this machine was a flashlight to
illuminate the registers.

   Marv Rubinstein