JSR STAT2 Push LOW PC Byte VIA R12 | Apple II specification

F796: 20 19 F7	181		JSR	STAT2	;PUSH LOW PC BYTE VIA R12
F799: A5 1F	182		LDA	R15H
F79B: 20 19 F7	183		JSR	STAT2	;PUSH HIGH-ORDER PC BYTE
F79E: 18	184	BR	CLC
F79F: B0 0E	185	BNC	BCS	BNC2	;NO CARRY TEST
F7A1: B1 1E	186	BR1	LDA	(R15L),Y	;DISPLACEMENT BYTE
F7A3: 10 01	187		BPL	BR2
F7A5: 88	188		DEY
F7A6: 65 1E	189	BR2	ADC	R15L	;ADD TO PC
F7A8: 85 1E	190		STA	R15L
F7AA: 98	191		TYA
F7AB: 65 1F	192		ADC	R15H
F7AD: 85 1F	193		STA	R15H
F7AF: 60	194	BNC2	RTS
F7B0: B0 EC	195	BC	BCS	BR
F7B2: 60	196		RTS
F7B3: 0A	197	BP	ASL		;DOUBLE RESULT-REG INDEX
F7B4: AA	198		TAX		;TO X REG FOR INDEXING
F7B5: B5 01	199		LDA	R0H,X	;TEST FOR PLUS
F7B7: 10 E8	200		BPL	BR1	;BRANCH IF SO
F7B9: 60	201		RTS
F7BA: 0A	202	BM	ASL		;DOUBLE RESULT-REG INDEX
F7BB: AA	203		TAX
F7BC: B5 01	204		LDA	R0H,X	;TEST FOR MINUS
F7BE: 30 E1	205		BMI	BR1
F7C0: 60	206		RTS
F7C1: 0A	207	BZ	ASL		;DOUBLE RESULT-REG INDEX
F7C2: AA	208		TAX
F7C3: B5 00	209		LDA	R0L,X	;TEST FOR ZERO
F7C5: 15 01	210		ORA	R0H,X	;(BOTH BYTES)
F7C7: F0 D8	211		BEQ	BR1	;BRANCH IF SO
F7C9: 60	212		RTS
F7CA: 0A	213	BNZ	ASL		;DOUBLE RESULT-REG INDEX
F7CB: AA	214		TAX
F7CC: B5 00	215		LDA	R0L,X	;TEST FOR NON-ZERO
F7CE: 15 01	216		ORA	R0H,X	;(BOTH BYTES)
F7D0: D0 CF	217		BNE	BR1	;BRANCH IF SO
F7D2: 60	218		RTS
F7D3: 0A	219	BM1	ASL		;DOUBLE RESULT-REG INDEX
F7D4: AA	220		TAX
F7D5: B5 00	221		LDA	R0L,X	;CHECK BOTH BYTES
F7D7: 35 01	222		AND	R0H,X	;FOR $FF (MINUS 1)
F7D9: 49 FF	223		EOR	#$FF
F7DB: F0 C4	224		BEQ	BR1	;BRANCH IF SO
F7DD: 60	225		RTS
F7DE: 0A	226	BNM1	ASL		;DOUBLE RESULT-REG INDEX
F7DF: AA	227		TAX
F7E0: B5 00	228		LDA	R0L,X
F7E2: 35 01	229		AND	R0H,X	;CHECK BOTH BYTES FOR NO $FF
F7E4: 49 FF	230		EOR	#$FF
F7E6: D0 B9	231		BNE	BR1	;BRANCH IF NOT MINUS 1
F7E8: 60	232	NUL	RTS
F7E9: A2 18	233	RS	LDX	#$18	;12*2 FOR R12 AS STACK POINTER
F7EB: 20 66 F7	234		JSR	DCR	;DECR STACK POINTER
F7EE: A1 00	235		LDA	(R0L,X)	;POP HIGH RETURN ADDRESS TO PC
F7F0: 85 1F	236		STA	R15H
F7F2: 20 66 F7	237		JSR	DCR	;SAME FOR LOW-ORDER BYTE
F7F5: A1 00	238		LDA	(R0L,X)
F7F7: 85 1E	239		STA	R15L
F7F9: 60	240		RTS
F7FA: 4C C7 F6	241	RTN	JMP	RTNZ

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.

JSR

STAT2

;PUSH LOW PC BYTE VIA R12

EOR

EOR

II specifications