Nxtadd TYA, Space Comm | Apple II guide

0542	E261				;*****	G COMMAND-RESTART PROCESSOR *****
0543	E261	20	37	E8	GO	JSR PSL1		;"/"
0544	E264	20	85	E7		JSR GCNT		;GET COUNT
0545	E267	20	F0	E9		JSR	CRLF
0546	E26A 4C		86	E2		JMP	GOBK1	;RESUME EXECUTION
0547	E26D AD		0E	A4	GOBK	LDA	REGF	;DISPLAY REGISTERS ?
0548	E270	F0	06			BEQ	GOBK0	;NO,BRANCH
0549	E272	20	32	E2		JSR	REG1	;SHOW THE SIX REG
0550	E275	20	24	EA		JSR	CRCK	;<CR>
0551	E278	20	07	E9	GOBK0	JSR	RCHEK	;SEE IF HE WANTS TO INTERRUPT
0552	E27B AD		0F	A4		LDA	DISFLG	;DISASSEMBLE CURRENT INSTR ?
0553	E27E F0		06			BEQ	GOBK1	;NO,BRANCH
0554	E280	20	6C	F4		JSR	DISASM	;DISASM THIS INSTRUCTION
0555	E283	20	13	EA		JSR	CRLOW
0556	E286	AE	24	A4	GOBK1	LDX SAVS		;RESTORE SAVED REGS FOR RTI
0557	E289	9A				TXS
0558	E28A AC		23	A4		LDY	SAVY
0559	E28D AE		22	A4		LDX	SAVX
0560	E290	AD	26	A4		LDA	SAVPC+1
0561	E293	48				PHA		;PUT PC ON STACK
0562	E294	AD	25	A4		LDA	SAVPC
0563	E297	48				PHA
0564	E298	AD	20	A4		LDA SAVPS		;STATUS ALSO
0565	E29B 48					PHA
0566	E29C AD		21	A4		LDA	SAVA
0567	E29F 40					RTI		;AND AWAY WE GO...
0568	E2A0
0569	E2A0				;*** / COMMAND-ALTER MEMORY ***
0570	E2A0 20		3E	E8	CHNGG	JSR	BLANK
0571	E2A3 20		DB E2			JSR	WRITAZ	;WRITE ADDR
0572	E2A6 20		3E	E8	CHNG1	JSR	BLANK
0573	E2A9 20		5D	EA		JSR	RD2	;GET VALUE
0574	E2AC 90		0A			BCC	CH2	;ISN'T SKIP OR DONE
0575	E2AE C9		20			CMP	#' '
0576	E2B0 D0		13			BNE	CH3	;NOT BLANK SO MUST BE DONE
0577	E2B2				;SKIP THIS		LOCATION
0578	E2B2 20		3E	E8		JSR	BLANK
0579	E2B5 4C		C0	E2		JMP	CH4
0580	E2B8				;IS ALTER
0581	E2B8 20		78	EB	CH2	JSR SADDR		;STORE ENTERED VALUE INTO MEMORY
0582	E2BB F0		03			BEQ CH4		;NO ERROR IN STORE
0583	E2BD 4C		33	EB		JMP MEMERR		;MEMORY WRITE ERROR
0584	E2C0 C8				CH4	INY
0585	E2C1 C0		04			CPY	#4
0586	E2C3 D0		E1			BNE	CHNG1	;GO AGAIN
0587	E2C5				;HAVE DONE		LINE OR HAVE <CR>
0588	E2C5 20		CD E2		CH3	JSR	NXTADD	;UPDATE THE ADDRESS
0589	E2C8 A9		0D			LDA	#CR	;CLEAR DISPL
0590	E2CA 4C		E9	FE		JMP PATC10		;ONLY ONE <CR> & BACK TO MONITOR
0591	E2CD
0592	E2CD 98				NXTADD TYA			;ADD Y TO ADDR+1,ADDR
0593	E2CE 18					CLC
0594	E2CF 6D		1C	A4		ADC	ADDR
0595	E2D2 8D		1C	A4		STA	ADDR
0596	E2D5 90		03			BCC	NXTA1
0597	E2D7 EE		1D	A4		INC	ADDR+1
0598	E2DA 60				NXTA1	RTS
0599	E2DB
0600	E2DB				;WRITE	CURRENT VALUE OF ADDR
0601	E2DB				;PART OF /		& SPACE COMM
0602	E2DB A0		00		WRITAZ	LDY	#0
0603	E2DD B9		1D	A4	WRITAD	LDA	ADDR+1,Y

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.

CMP

NXTADD TYA

ADC

& SPACE COMM

II specifications