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Path: utzoo!linus!decvax!tektronix!orca!mako!jans
From: jans@mako.UUCP (Jan Steinman)
Newsgroups: net.arch
Subject: To Flag Or Not To Flag...
Message-ID: <353@mako.UUCP>
Date: Thu, 1-Nov-84 14:58:03 EST
Article-I.D.: mako.353
Posted: Thu Nov  1 14:58:03 1984
Date-Received: Sat, 3-Nov-84 05:55:59 EST
Organization: Tektronix, Wilsonville OR
Lines: 22


I've been writing assembly code for over seven years, and I've noticed two,
widely differing philosophies on CPU condition code flag usage.  The
"Flaggers", such as the 68000 family, try to keep the flags full of useful
information at all times by affecting as many of them as makes sense with
each operation, while the "Ask-For-Its", such as the 8080 and NS32000
families, make you beg for every bit.

I can see arguments for each side, (as obviously Motorola did when they
split with orthogonality in limiting address registers' ability to flip
flags) but lean toward "Flaggers" as exhibiting preferable behavior.

What do others prefer?  Why did these machines go their separate ways?
Any insiders care to comment?

(The onions expressed are carefully perfumed to avoid offending anyone's
 sensibilities and have nothing to do with the onions in any cafeteria
 in any institution where I may, or may not, have previously eaten or am
 presently eating.)  (Let the lawyers munch on that a while.)
-- 
:::::: Jan Steinman		Box 1000, MS 61-161	(w)503/685-2843 ::::::
:::::: tektronix!tekecs!jans	Wilsonville, OR 97070	(h)503/657-7703 ::::::