Apple II manual Log, Fadd, Fsub, Fmul, Fdiv, Fix, Fcompl, +- Sign BIT, Presumed Decimal Point

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TOPIC -- Apple II -- IA Floating point article

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Interface Age, November 1976, pages 103-111.

Floating Point Routines for the 6502*

by Roy Rankin

Department of Mechanical Engineering, Stanford University

and Steve Wozniak

Apple Computer Company

*First appeared in Dr. DOBB's Journal of Computer Calisthenics & Orthodontia, Box 310, Menlo Park, CA 94025

The following floating point routines represent a joint effort between Steve Wozniak who wrote the basic float- ing point routines of FADD, FSUB, FMUL, FDIV and their support routines and myself, Roy Rankin, who added FIX, FLOAT, LOG, LOG10, and EXP. The basic floating point routines are failry Machine dependent, but the transcendental programs should be very easy to transport from one machine to another. The routines consist of the following math functions

* LOG	Natural log
* LOG10	Base 10 log
* EXP	Exponential
* FADD	Floating add
* FSUB	Floating subtraction
* FMUL	Floating multiplication
* FDIV	Floating division
* FIX	Convert floating to fixed
* FLOAT	Convert fixed to floating

Two additional routines exchange the contents of exp/mant1 with exp/mant2 and compliments exp/

mant1. These routines					are
SWAP		Exchange			the contents of exp/mant 1 with
		exp/mant			2
FCOMPL		Compliment exp/mant 1
Floating point numbers					are represented by 4 bytes as
shown in the following
+- SIGN BIT		+-	SIGN BIT
	0 = +		0	= +
	1 = -		1	= -
v		v
S		S	+-		PRESUMED DECIMAL POINT
B		B	v

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