Backwd LDA, Forwrd LDA | Apple II manual

3911	FDBB 38	CMPBR1 SEC			;COMPUTE BRANCH RELATIVE ADDRESS
3912	FDBC AD 35 A4		LDA	OPCODE+1
3913	FDBF ED 26 01		SBC	MOVAD
3914	FDC2 8D 35 A4		STA	OPCODE+1
3915	FDC5 AD 36 A4		LDA	OPCODE+2
3916	FDC8 ED 27 01		SBC	MOVAD+1
3917	FDCB 8D 36 A4		STA	OPCODE+2
3918	FDCE C9 00		CMP	#00
3919	FDD0 F0 0E		BEQ	FORWRD
3920	FDD2 C9 FF		CMP	#$FF
3921	FDD4 F0 03		BEQ	BACKWD
3922	FDD6 4C C5 FC	ERRJMP JMP		ERRORM
3923	FDD9 AD 35 A4	BACKWD LDA		OPCODE+1	;CHECK IN RANGE
3924	FDDC 30 09		BMI	OK
3925	FDDE 10 F6		BPL	ERRJMP
3926	FDE0 AD 35 A4	FORWRD LDA		OPCODE+1
3927	FDE3 10 02		BPL	OK
3928	FDE5 30 EF		BMI	ERRJMP
3929	FDE7 A9 02	OK	LDA	#02	;SET UP FOR STASH
3930	FDE9 8D 2F A4		STA	BYTESM
3931	FDEC 4C 2C FD		JMP	STASH
3932	FDEF
3933	FDEF	;###### SUBROUTINE ########
3934	FDEF	;SUBROUTINE FOR DETERMINING X OR Y OR NEITHER
3935	FDEF A2 04	XORY	LDX	#04
3936	FDF1 BD 33 01	XORYZ	LDA	ADFLD,X
3937	FDF4 C9 2C		CMP	#','
3938	FDF6 D0 04		BNE	XORY1
3939	FDF8 E8		INX
3940	FDF9 BD 33 01		LDA	ADFLD,X
3941	FDFC C9 58	XORY1	CMP	#'X'
3942	FDFE F0 03		BEQ	ISX
3943	FE00 C9 59		CMP	#'Y'
3944	FE02	XORYRT
3945	FE02 60		RTS		;NOT ZERO IS NOT X OR NOT Y
3946	FE03 18	ISX	CLC		;CARRY SET IS Y
3947	FE04 90 FC		BCC XORYRT		; CARRY CLEAR IS X
3948	FE06	;####### END OF SUB ########
3949	FE06
3950	FE06	; INPUT FOR MNEMONIC CODE
3951	FE06 A0 00	MNEM	LDY	#00
3952	FE08 8C 34 A4		STY	OPCODE
3953	FE0B 8C 35 A4		STY	OPCODE+1
3954	FE0E 8C 36 A4		STY	OPCODE+2	;CLEARS OPCODE FOR NEW INPUT
3955	FE11 8C 26 01		STY	MOVAD	;CLEARS UNUSED BIT IN FINAL FORMAT
3956	FE14 20 5F E9	RDLUP	JSR	RDRUP
3957	FE17 C9 2A		CMP	#'*'	;COMMAND TO LOAD POINTER
3958	FE19 F0 58		BEQ	STLOAD	;GO TO SET CURRENT ADDRESS POINTER
3959	FE1B C9 20		CMP	#' '	;IGNORE SPACE BAR INPUT
3960	FE1D F0 F5		BEQ	RDLUP
3961	FE1F 29 1F		AND	#$1F	;MASK OFF UPPER 3 BITS
3962	FE21 99 30 01		STA	CH,Y
3963	FE24 98		TYA
3964	FE25 AA		TAX		;Y----> X
3965	FE26 FE 30 01		INC CH,X		;FORMAT TO MATCH DISASSEMBLER TBL
3966	FE29 C8		INY
3967	FE2A C0 03		CPY #03		;REPEAT FOR EACH OF 3 CHARACTERS
3968	FE2C D0 E6		BNE	RDLUP
3969	FE2E
3970	FE2E	;COMPRESS 3 FORMATED CHARACTERS TO MOVAD & MOVAD+1
3971	FE2E A0 03		LDY #03		;SET UP OUTER LOOP
3972	FE30 B9 2F 01	OUTLUP LDA CH-1,Y			;COMPRESS 3 CHARACTERS

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 Backwd LDA, Forwrd LDA

Models: II

CMP

CMP

BACKWD LDA

FORWRD LDA

CMP

CMP

CMP

CMP

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TAX

II specifications