Floating Point Subroutine Descriptions

- 3	81	A0	00	00
- 4	81	80	00	00
- 5	82	B0	00	00
- 7	82	90	00	00
-12	83	A0	00	00
-15	83	88	00	00
-17	84	BC 00 00
-20	84	B0	00	00
-60	85	88	00	00

FLOATING POINT SUBROUTINE DESCRIPTIONS

FCOMPL subroutine (address $F4A4)

Purpose: FCOMPL is used to negate floating point numbers.

Entry: A normalized or unnormalized value is in FP1 (floating point accumulator 1).

Uses: NORM, RTLOG.

Exit: The value in FP1 is negated and then normalized to retain precision. The 3-byte FP1 extension, E, may also be altered but FP2 and SIGN are not disturbed. The 6502 A-REG is altered and the X-REG is cleared. The Y-REG is not disturbed.

Caution: Attempting to negate -2^128 will result in an overflow since +2^128 is not representable, and a jump to location $3F5 will be executed, with the following contents in FP1.

	_____		_____		_____		_____

FP1:	0		$80		0		0
_____		_____		_____		_____

X1 M1

Example: Prior to calling FCOMPL, FP1 contains +15.

	_____		_____		_____		_____

FP1:	$83		$78		0		0	(+15)
_____		_____		_____		_____

X1 M1

After calling FCOMPL as a subroutine, FP1 contains -15.

	_____		_____		_____		_____

FP1:	$83		$88		0		0	(+15)
_____		_____		_____		_____
	X1		M1

II specifications

The Apple II, launched in April 1977, was one of the first highly successful mass-produced microcomputer products. It marked a significant leap in personal computing, setting standards for future developments in the industry. Created by Steve Wozniak and Steve Jobs, the Apple II differentiated itself with its user-friendly design, appealing aesthetics, and robust capabilities.

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Apple II manual Floating Point Subroutine Descriptions

Models: II

FLOATING POINT SUBROUTINE DESCRIPTIONS

II specifications