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From: miller@uiucdcs.UUCP (miller )
Newsgroups: net.micro.cbm
Subject: Re: ROM-antics - (nf)
Message-ID: <5653@uiucdcs.UUCP>
Date: Wed, 15-Feb-84 03:27:19 EST
Article-I.D.: uiucdcs.5653
Posted: Wed Feb 15 03:27:19 1984
Date-Received: Thu, 16-Feb-84 06:05:07 EST
Lines: 25

#R:decwrl:-553200:uiucdcs:36100044:000:727
uiucdcs!miller    Feb 15 00:50:00 1984


     By golly Jeff, you're right!  It is F1 = F2 - F1 on the c64 floating point
routines (and not F1 - F2).  My mistake there.  Actually, subtraction is very
short, so I have reproduced it below for those that are interested:

; subtraction
;
    ORG  $B853
    LDA  102    ;get sign of F1
    EOR# $FF    ;complement F1 sign
    STA  102    ;replace so F1=-1*F1
    EOR  110    ;compare F1, F2 signs
    STA  111    ;set sign compare flag for addition
    LDA  97     ;setup for add too
    JMP  $B86A  ;goto addition subroutine

     I wrote a note last week on the variable storage question so I won't
reproduce that here again.
     Thanks for pointing that out, Jeff.  Sorry for the mixup...

A. Ray Miller
Univ Illinois