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From: wapd@houxj.UUCP (Bill Dietrich)
Newsgroups: net.micro
Subject: Re: 8086 et al status bits question.
Message-ID: <450@houxj.UUCP>
Date: Fri, 21-Dec-84 16:48:29 EST
Article-I.D.: houxj.450
Posted: Fri Dec 21 16:48:29 1984
Date-Received: Sat, 22-Dec-84 07:38:48 EST
References: <435@gitpyr.UUCP>, <12@spar.UUCP>
Organization: AT&T Bell Labs, Holmdel NJ
Lines: 25



I haven't used an 8080-type processor in 8 years or so,
but I believe the reason for INC/DEC not touching CARRY
is to allow multiple-digit or high-precision math.  To
add two 200 digit numbers, for example (in pseudo-code) :

	p1 = pointer to digit of number 1 (source)
	p2 = pointer to digit of number 2 (source)
	p3 = pointer to digit of number 3 (destination)
	*px means digit pointed to by px

	counter = 200
loop:
	add with carry *p1 and *p2 putting in *p3, generating carry
	INC p1
	INC p2
	INC p3
	DEC counter
	JUMP to loop if counter not zero


					Bill Dietrich
					houxj!wapd