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TOPIC -- Apple II -- Red Book Floating point listing

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Apple II Reference Manual (Red Book), January 1978, pages 94-95.

	***********************
	*				*
	*	APPLE-II FLOATING			*
	*	POINT ROUTINES			*
	*				*
	*	COPYRIGHT 1977 BY			*
	* APPLE COMPUTER INC. *
	*				*
	* ALL RIGHTS RESERVED *
	*				*
	*	S. WOZNIAK			*
	*				*
	***********************
	TITLE "FLOATING POINT ROUTINES"
	SIGN		EPZ	$F3
	X2		EPZ	$F4
	M2		EPZ	$F5
	X1		EPZ	$F8
	M1		EPZ	$F9
	E		EPZ	$FC
	OVLOC		EQU	$3F5
			ORG	$F425
F425: 18	ADD		CLC		CLEAR CARRY
F426: A2 02			LDX	#$2	INDEX FOR 3-BYTE ADD.
F428: B5 F9	ADD1		LDA	M1,X
F42A: 75 F5			ADC	M2,X	ADD A BYTE OF MANT2 TO MANT1
F42C: 95 F9			STA	M1,X
F42E: CA			DEX		INDEX TO NEXT MORE SIGNIF. BYTE.
F42F: 10 F7			BPL	ADD1	LOOP UNTIL DONE.
F431: 60			RTS		RETURN
F432: 06 F3	MD1		ASL	SIGN	CLEAR LSB OF SIGN.
F434: 20 37 F4			JSR	ABSWAP	ABS VAL OF M1, THEN SWAP WITH M2
F437: 24 F9	ABSWAP		BIT	M1	MANT1 NEGATIVE?
F439: 10 05			BPL	ABSWAP1	NO, SWAP WITH MANT2 AND RETURN.
F43B: 20 A4 F4			JSR	FCOMPL	YES, COMPLEMENT IT.
F43E: E6 F3			INC	SIGN	INCR SIGN, COMPLEMENTING LSB.
F440: 38	ABSWAP1		SEC		SET CARRY FOR RETURN TO MUL/DIV.
F441: A2 04	SWAP		LDX	#$4	INDEX FOR 4 BYTE SWAP.
F443: 94 FB	SWAP1		STY	E-1,X
F445: B5 F7			LDA	X1-1,X	SWAP A BYTE OF EXP/MANT1 WITH
F447: B4 F3			LDY	X2-1,X	EXP/MANT2 AND LEAVE A COPY OF
F449: 94 F7			STY	X1-1,X	MANT1 IN E (3 BYTES). E+3 USED
F44B: 95 F3			STA	X2-1,X
F44D: CA			DEX		ADVANCE INDEX TO NEXT BYTE
F44E: D0 F3			BNE	SWAP1	LOOP UNTIL DONE.
F450: 60			RTS		RETURN
F451: A9 8E	FLOAT		LDA	#$8E	INIT EXP1 TO 14,
F453: 85 F8			STA	X1	THEN NORMALIZE TO FLOAT.
F455: A5 F9	NORM1		LDA	M1	HIGH-ORDER MANT1 BYTE.
F457: C9 C0			CMP	#$C0	UPPER TWO BITS UNEQUAL?
F459: 30 0C			BMI	RTS1	YES, RETURN WITH MANT1 NORMALIZED
F45B: C6 F8			DEC	X1	DECREMENT EXP1.
F45D: 06 FB			ASL	M1+2
F45F: 26 FA			ROL	M1+1	SHIFT MANT1 (3 BYTES) LEFT.

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.

One of the standout features of the Apple II was its open architecture, which allowed users to expand and enhance the computer's functionality. This design enabled hundreds of third-party hardware and software developers to contribute to its ecosystem, resulting in an array of peripherals, including printers, modems, and storage devices. The Apple II utilized a MOS Technology 6502 microprocessor running at a clock speed of 1 MHz. Initially equipped with 4 KB of RAM, the machine could be expanded to 48 KB, accommodating more complex applications and programs.

The Apple II was also notable for its colorful graphics. It was one of the first computers to support color display, offering a 6-color palette with a resolution of 280x192 pixels in 16 colors when using its Color Graphics Card. This feature significantly enhanced the visual appeal of games and educational software developed for the platform, making computing more accessible and entertaining for various audiences.

Apple's commitment to user experience was evident in the design of the machine. It featured an integrated keyboard and a plastic case, which was both durable and visually appealing. The self-contained design included drive bays for floppy disk drives, allowing for quicker data access than traditional tape drives. It also supported audio output, enabling sound effects and music, a novelty at the time.

The introduction of the Apple DOS operating system further underscored the machine's capabilities. DOS streamlined file management and made it easier for users to navigate and manage their data. The combination of hardware and software positioned the Apple II as an educational tool and a gaming platform, fostering a vibrant software ecosystem.

The Apple II family continued to evolve, with variations like the Apple II+, IIe, and IIgs being introduced over the years. These iterations brought enhancements in memory, processing power, and graphics capabilities. The legacy of the Apple II endures, not only as a foundational product in personal computing but also as a symbol of innovation that paved the way for future advancements in technology. Its impact is still felt today, as it inspired countless developers and shaped the trajectory of the computer industry.

Apple II manual Org, Clc, Sta, Bne, Bmi, Dec, Rol

Models: II

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II specifications