Apple II
Apple II in a common 1977 configuration, with a 9" monochrome monitor, game paddles, and a Red Book-recommended Panasonic RQ-309DS cassette deck
DeveloperSteve Wozniak (lead designer)
ManufacturerApple Computer, Inc.
Product familyApple II series
Release dateJune 1977 (1977-06)[1]
Introductory priceUS$1,298 (equivalent to $6,270 in 2022)
DiscontinuedMay 1979 (1979-05)
Operating systemInteger BASIC / Apple DOS
CPUMOS Technology 6502
@ 1.023 MHz
Memory4, 8, 12, 16, 20, 24, 32, 36, 48, or 64 KiB
StorageAudio cassette,
Disk II (5.25-inch, 140 KB, Apple)
DisplayNTSC video out (built-in RCA connector)
GraphicsLo-res: 40×48, 16-color
Hi-res: 280×192, 6-color
Sound1-bit speaker (built-in)
1-bit cassette input (built-in microphone jack)
1-bit cassette output (built-in headphone jack)
InputUpper-case keyboard, 52 keys
Controller inputPaddles
ConnectivityParallel port card (Apple and third party); Serial port card (Apple and third party); SCSI
PredecessorApple I
SuccessorApple II Plus
An Apple II computer with an external modem

The Apple II (stylized as apple ][) is an early personal computer that was created by Apple Inc. It was one of the first successful mass-produced microcomputer products, and it played a significant role in the early development of the personal computer industry.[2] It has an 8-bit microprocessor.

The Apple II was designed primarily by Steve Wozniak; Jerry Manock developed the design of Apple II's foam-molded plastic case,[3] Rod Holt developed the switching power supply,[4] while Steve Jobs was not involved in the design or development of the computer.[5] It was introduced by Jobs and Wozniak at the 1977 West Coast Computer Faire, and marks Apple's first launch of a personal computer aimed at a consumer market—branded toward American households rather than businessmen or computer hobbyists.[6]

The three computers that Byte magazine referred to as the "1977 Trinity" of home computing: Commodore PET 2001, Apple II, and TRS-80 Model I

Byte magazine referred to the Apple II, Commodore PET 2001, and TRS-80 as the "1977 Trinity".[7] As the Apple II had the defining feature of being able to display color graphics, the Apple logo was redesigned to have a spectrum of colors.[8][9]

The Apple II is the first model in the Apple II series, followed by Apple II+, Apple IIe, Apple IIc, Apple IIc Plus, and the 16-bit Apple IIGS—all of which remained compatible. Production of the last available model, Apple IIe, ceased in November 1993.[10]

In 2006, PC World wrote that the Apple II was the greatest PC of all time.[11]

History

By 1976, Steve Jobs had convinced product designer Jerry Manock (who had formerly worked at Hewlett Packard designing calculators) to create the "shell" for the Apple II—a smooth case inspired by kitchen appliances that concealed the internal mechanics.[6] The earliest Apple II computers were assembled in Silicon Valley and later in Texas;[12] printed circuit boards were manufactured in Ireland and Singapore. The first computers went on sale on June 10, 1977[13][14] with an MOS Technology 6502 microprocessor running at 1.023 MHz (2⁄7 of the NTSC color subcarrier), two game paddles[15] (bundled until 1980, when they were found to violate FCC regulations),[16] 4 KiB of RAM, an audio cassette interface for loading programs and storing data, and the Integer BASIC programming language built into ROMs. The video controller displayed 24 lines by 40 columns of monochrome, uppercase-only text on the screen (the original character set matches ASCII characters 20h to 5Fh), with NTSC composite video output suitable for display on a TV monitor or on a regular TV set (by way of a separate RF modulator).

The original retail price of the computer with 4 KiB of RAM was US$1,298 (equivalent to $6,270 in 2022)[17] and with the maximum 48 KiB of RAM, it was US$2,638 (equivalent to $12,740 in 2022)[18] To reflect the computer's color graphics capability, the Apple logo on the casing has rainbow stripes,[19] which remained a part of Apple's corporate logo until early 1998. Perhaps most significantly, the Apple II was a catalyst for personal computers across many industries; it opened the doors to software marketed at consumers.[6]

Certain aspects of the system's design were influenced by Atari's arcade video game Breakout (1976), which was designed by Wozniak, who said: "A lot of features of the Apple II went in because I had designed Breakout for Atari. I had designed it in hardware. I wanted to write it in software now".[20] This included his design of color graphics circuitry, the addition of game paddle support and sound, and graphics commands in Integer BASIC, with which he wrote Brick Out, a software clone of his own hardware game.[21] Wozniak said in 1984: "Basically, all the game features were put in just so I could show off the game I was familiar with—Breakout—at the Homebrew Computer Club. It was the most satisfying day of my life [when] I demonstrated Breakout—totally written in BASIC. It seemed like a huge step to me. After designing hardware arcade games, I knew that being able to program them in BASIC was going to change the world."[22]

Overview

In the May 1977 issue of Byte, Steve Wozniak published a detailed description of his design; the article began, "To me, a personal computer should be small, reliable, convenient to use, and inexpensive."[23]

The Apple II used peculiar engineering shortcuts to save hardware and reduce costs, such as:

  • Taking advantage of the way the 6502 processor accesses memory: it occurs only on alternate phases of the clock cycle; video generation circuitry memory access on the otherwise unused phase avoids memory contention issues and interruptions of the video stream;
  • This arrangement simultaneously eliminated the need for a separate refresh circuit for DRAM chips, as video transfer accessed each row of dynamic memory within the timeout period. In addition, it did not require separate RAM chips for video RAM, while the PET and TRS-80 had SRAM chips for video;
  • Apart from the 6502 CPU and a few support chips, the vast majority of the semiconductors used were 74LS low-power Schottky chips;
  • Rather than use a complex analog-to-digital circuit to read the outputs of the game controller, Wozniak used a simple timer circuit, built around a quad 555 timer IC called a 558, whose period is proportional to the resistance of the game controller, and he used a software loop to measure the timers;
  • A single 14.31818 MHz master oscillator (fM) was divided by various ratios to produce all other required frequencies, including microprocessor clock signals (fM/14), video transfer counters, and color-burst samples (fM/4). A solderable jumper on the main board allowed to switch between European 50 Hz and USA 60 Hz video.

The text and graphics screens have a complex arrangement. For instance, the scanlines were not stored in sequential areas of memory. This complexity was reportedly due to Wozniak's realization that the method would allow for the refresh of dynamic RAM as a side effect (as described above). This method had no cost overhead to have software calculate or look up the address of the required scanline and avoided the need for significant extra hardware. Similarly, in high-resolution graphics mode, color is determined by pixel position and thus can be implemented in software, saving Wozniak the chips needed to convert bit patterns to colors. This also allowed to draw text with subpixel rendering, since orange and blue pixels appear half a pixel-width farther to the right on the screen than green and purple pixels.[24]

The Apple II at first used data cassette storage, like most other microcomputers of the time. In 1978, the company introduced an external 5+1⁄4-inch floppy disk drive, called Disk II (stylized as Disk ][), attached through a controller card that plugs into one of the computer's expansion slots (usually slot 6). The Disk II interface, created by Wozniak, is regarded as an engineering masterpiece for its economy of electronic components.[25][26]

The approach taken in the Disk II controller is typical of Wozniak's designs. With a few small-scale logic chips and a cheap PROM (programmable read-only memory), he created a functional floppy disk interface at a fraction of the component cost of standard circuit configurations.

Case design

The first production Apple II computers had hand-molded cases; these had visible bubbles and other lumps in them from the imperfect plastic molding process, which was soon switched to machine molding.[27] In addition, the initial case design had no vent openings, causing high heat buildup from the PCB and resulting in the plastic softening and sagging. Apple added vent holes to the case within three months of production; customers with the original case could have them replaced at no charge.

PCB revisions

The Apple II's printed circuit board (PCB) underwent several revisions, as Steve Wozniak made modifications to it. The earliest version was known as Revision 0, and the first 6,000 units shipped used it. Later revisions added a color killer circuit to prevent color fringing when the computer was in text mode, as well as modifications to improve the reliability of cassette I/O. Revision 0 Apple IIs powered up in an undefined mode and had garbage on-screen, requiring the user to press Reset. This was eliminated in later board revisions. Revision 0 Apple IIs could display only four colors in hi-res mode, but Wozniak was able to increase this to six hi-res colors on later board revisions.

The PCB had three RAM banks for a total of 24 RAM chips. Original Apple IIs had jumper switches to adjust RAM size, and RAM configurations could be 4, 8, 12, 16, 20, 24, 32, 36, or 48 KiB. The three smallest memory configurations used 4kx1 DRAMs, with larger ones using 16kx1 DRAMs, or mix of 4-kilobyte and 16-kilobyte banks (the chips in any one bank have to be the same size). The early Apple II+ models retained this feature, but after a drop in DRAM prices, Apple redesigned the circuit boards without the jumpers, so that only 16kx1 chips were supported. A few months later, they started shipping all machines with a full 48 KiB complement of DRAM.

Unlike most machines, all integrated circuits on the Apple II PCB were socketed; although this cost more to manufacture and created the possibility of loose chips causing a system malfunction, it was considered preferable to make servicing and replacement of bad chips easier.

The Apple II PCB lacks any means of generating an interrupt request, although expansion cards may generate one. Program code had to stop everything to perform any I/O task; like many of the computer's other idiosyncrasies, this was due to cost reasons and Steve Wozniak assuming interrupts were not needed for gaming or using the computer as a teaching tool.

Display and graphics

Color on the Apple II series uses a quirk of the NTSC television signal standard, which made color display relatively easy and inexpensive to implement. The original NTSC television signal specification was black and white. Color was added later by adding a 3.58-megahertz subcarrier signal that was partially ignored by black-and-white TV sets. Color is encoded based on the phase of this signal in relation to a reference color burst signal. The result is that the position, size, and intensity of a series of pulses define color information. These pulses can translate into pixels on the computer screen, with the possibility of exploiting composite artifact colors.

The Apple II display provides two pixels per subcarrier cycle. When the color burst reference signal is turned on and the computer attached to a color display, it can display green by showing one alternating pattern of pixels, magenta with an opposite pattern of alternating pixels, and white by placing two pixels next to each other. Blue and orange are available by tweaking the pixel offset by half a pixel-width in relation to the color-burst signal. The high-resolution display offers more colors by compressing more (and narrower) pixels into each subcarrier cycle.

The coarse, low-resolution graphics display mode works differently, as it can output a pattern of dots per pixel to offer more color options. These patterns are stored in the character generator ROM, and replace the text character bit patterns when the computer is switched to low-res graphics mode. The text mode and low-res graphics mode use the same memory region and the same circuitry is used for both.

A single HGR page occupied 8 KiB of RAM; in practice this meant that the user had to have at least 12 KiB of total RAM to use HGR mode and 20 KiB to use two pages. Early Apple II games from the 1977–79 period often ran only in text or low-resolution mode in order to support users with small memory configurations; HGR not being near universally supported by games until 1980.

Sound

Rather than a dedicated sound-synthesis chip, the Apple II has a toggle circuit that can only emit a click through a built-in speaker or a line-out jack; all other sounds (including two-, three- and, eventually, four-voice music and playback of audio samples and speech synthesis) are generated entirely by software that clicked the speaker at just the right times. Similar techniques are used for cassette storage: cassette output works the same as the speaker, and input is a simple zero-crossing detector that serves as a relatively crude (1-bit) audio digitizer. Routines in machine ROM encode and decode data in frequency-shift keying for the cassette.

Programming languages

Initially, the Apple II was shipped with Integer BASIC encoded in the motherboard ROM chips. Written by Wozniak, the interpreter enabled users to write software applications without needing to purchase additional development utilities. Written with game programmers and hobbyists in mind, the language only supported the encoding of numbers in 16-bit integer format. Since it only supported integers between -32768 and +32767 (signed 16-bit integer), it was less suitable to business software, and Apple soon received complaints from customers. Because Steve Wozniak was busy developing the Disk II hardware, he did not have time to modify Integer BASIC for floating point support. Apple instead licensed Microsoft's 6502 BASIC to create Applesoft BASIC.

Disk users normally purchased a so-called Language Card, which had Applesoft in ROM, and was located below the Integer BASIC ROM in system memory. The user could switch between either BASIC by typing FP or INT in BASIC prompt. Apple also offered a different version of Applesoft for cassette users, which occupied low memory, and was started by using the LOAD command in Integer BASIC.

As shipped, Apple II incorporated a machine code monitor with commands for displaying and altering the computer's RAM, either one byte at a time, or in blocks of 256 bytes at once. This enabled programmers to write and debug machine code programs without further development software. The computer powers on into the monitor ROM, displaying a * prompt. From there, Ctrl+B enters BASIC, or a machine language program can be loaded from cassette. Disk software can be booted with Ctrl+P followed by 6, referring to Slot 6 which normally contained the Disk II controller.

A 6502 assembler was soon offered on disk,[28] and later the UCSD compiler and operating system for the Pascal language were made available. The Pascal system requires a 16 KiB RAM card to be installed in the language card position (expansion slot 0) in addition to the full 48 KiB of motherboard memory.

Manual

The first 1,000 or so Apple IIs shipped in 1977 with a 68-page mimeographed "Apple II Mini Manual", hand-bound with brass paper fasteners. This was the basis for the Apple II Reference Manual, which became known as the Red Book for its red cover, published in January 1978. All existing customers who sent in their warranty cards were sent free copies of the Red Book. The Apple II Reference Manual contained the complete schematic of the entire computer's circuitry, and a complete source listing of the "Monitor" ROM firmware that served as the machine's BIOS.

An Apple II manual signed by Steve Jobs in 1980 with the inscription "Julian, your generation is the first to grow up with computers. Go change the world." sold at auction for $787,484 in 2021.[29]

Operating system

The original Apple II provided an operating system in ROM along with a BASIC variant called Integer BASIC. The only form of storage available was cassette tape which was inefficiently slow and, worse, unreliable. In 1977 when Apple decided against the popular but clunky CP/M operating system for Wozniak's innovative disk controller design, it contracted Shepardson Microsystems for $13,000 to write an Apple DOS for the Apple II series.[30][31] At Shepardson, Paul Laughton developed the crucial disk drive software in just 35 days, a remarkably short deadline by any standard.[32] Apple's Disk II 5+1⁄4-inch floppy disk drive was released in 1978. The final and most popular version of this software was Apple DOS 3.3.

Apple DOS was superseded by ProDOS, which supported a hierarchical filesystem and larger storage devices. With an optional third-party Z80-based expansion card,[33] the Apple II could boot into the CP/M operating system and run WordStar, dBase II, and other CP/M software. With the release of MousePaint in 1984 and the Apple IIGS in 1986, the platform took on the look of the Macintosh user interface, including a mouse.

Apple released Applesoft BASIC in 1977, a more advanced variant of the language which users could run instead of Integer BASIC for more capabilities.

Some commercial Apple II software booted directly and did not use standard DOS disk formats. This discouraged the copying or modifying of the software on the disks, and improved loading speed.

Third-party devices and applications

When the Apple II initially shipped in June 1977, no expansion cards were available for the slots. This meant that the user did not have any way of connecting a modem or a printer. One popular hack involved connecting a teletype machine to the cassette output.

Wozniak's open-architecture design and Apple II's multiple expansion slots permitted a wide variety of third-party devices, including peripheral cards, such as serial controllers, display controllers, memory boards, hard disks, networking components, and real-time clocks. There were plug-in expansion cards—such as the Z-80 SoftCard—that permitted Apple II to use the Z80 processor and run programs for the CP/M operating system,[33] including the dBase II database and the WordStar word processor. The Z80 card also allowed the connection to a modem, and thereby to any networks that a user might have access to. In the early days, such networks were scarce. But they expanded significantly with the development of bulletin board systems in later years. There was also a third-party 6809 card that allowed OS-9 Level One to be run. Third-party sound cards greatly improved audio capabilities, allowing simple music synthesis and text-to-speech functions. Apple II accelerator cards doubled or quadrupled the computer's speed.

Early Apple IIs were often sold with a Sup'R'Mod, which allowed the composite video signal to be viewed in a television.

The Soviet Union radio-electronics industry designed Apple II-compatible computer Agat. Roughly 12,000 Agat 7 and 9 models were produced and they were widely used in Soviet schools.[34] Agat 9 computers could run "Apple II" compatibility and native modes. "Apple II" mode allowed to run a wider variety of (presumably pirated) Apple II software, but at the expense of less RAM. Because of that Soviet developers preferred native mode over "Apple II" compatibility mode.

Reception

Advertisement for Apple II (1977)

Jesse Adams Stein wrote, "As the first company to release a 'consumer appliance' micro-computer, Apple Computer offers us a clear view of this shift from a machine to an appliance." But the company also had "to negotiate the attitudes of its potential buyers, bearing in mind social anxieties about the uptake of new technologies in multiple contexts. The office, the home and the 'office-in-the-home' were implicated in these changing spheres of gender stereotypes and technological development."[35] After seeing a crude, wire-wrapped prototype demonstrated by Wozniak and Steve Jobs in November 1976,[15] Byte predicted in April 1977, that the Apple II "may be the first product to fully qualify as the 'appliance computer' ... a completed system which is purchased off the retail shelf, taken home, plugged in and used". The computer's color graphics capability especially impressed the magazine.[36] The magazine published a favorable review of the computer in March 1978, concluding: "For the user that wants color graphics, the Apple II is the only practical choice available in the 'appliance' computer class."[15]

Personal Computer World in August 1978 also cited the color capability as a strength, stating that "the prime reason that anyone buys an Apple II must surely be for the colour graphics". While mentioning the "oddity" of the artifact colors that produced output "that is not always what one wishes to do", it noted that "no-one has colour graphics like this at this sort of price". The magazine praised the sophisticated monitor software, user expandability, and comprehensive documentation. The author concluded that "the Apple II is a very promising machine" which "would be even more of a temptation were its price slightly lower ... for the moment, colour is an Apple II".[37]

Although it sold well from the launch, the initial market was to hobbyists and computer enthusiasts. Sales expanded exponentially into the business and professional market, when the spreadsheet program VisiCalc was launched in mid-1979. VisiCalc is credited as the defining killer app in the microcomputer industry.

By the end of 1977 Apple had sales of $775,000 for the fiscal year, which included sales of the Apple I. This puts Apple clearly behind the others of the "holy trinity" of the TRS-80 and Commodore PET, even though the TRS-80 was launched last of the three. [38] However, during the first five years of operations, revenues doubled about every four months. Between September 1977 and September 1980, annual sales grew from $775,000 to $118 million.[39] During this period the sole products of the company were the Apple II and its peripherals, accessories, and software.

In 2006, PC World wrote that the Apple II was the greatest PC of all time.[40]

References

  1. ↑ Weyhrich, Steven (July 10, 2010). "1969-1977". Apple II History. Archived from the original on May 17, 2022. Retrieved October 2, 2016.
  2. ↑ Reimer, Jeremy (December 14, 2005). "Total share: 30 years of personal computer market share figures". Ars Technica. Archived from the original on December 4, 2008. Retrieved May 25, 2010.
  3. ↑ Isaacson, Walter (2011). Steve Jobs. Simon & Schuster. ISBN 9781451648546. OCLC 859338048.
  4. ↑ Wozniak, Steve. "Comment From e-mail: Why didn't the early Apple II's use Fans?". woz.org. Archived from the original on December 26, 2015. Retrieved May 10, 2015.
  5. ↑ "Steve Jobs 'played no role at all' in designing the Apple I or Apple II computers, Woz says". Yahoo Finance. September 2, 2015. Retrieved December 5, 2023.
  6. 1 2 3 Stein, Jesse Adams (2011). "Domesticity, Gender and the 1977 Apple II Personal Computer". Design and Culture. 3 (2): 193–216. doi:10.2752/175470811X13002771867842. hdl:10453/30296. S2CID 143648126.
  7. ↑ "Most Important Companies". Byte. September 1995. Archived from the original on June 18, 2008. Retrieved June 10, 2008.
  8. ↑ Steven Weyhrich (April 21, 2002). "Apple II History Chapter 4". Archived from the original on September 25, 2006. Retrieved November 16, 2006.
  9. ↑ "Interview with Rob Janoff, designer of the Apple logo". July 20, 2020. Archived from the original on October 24, 2017. Retrieved September 12, 2020.
  10. ↑ Weyhrich, Steven (May 16, 2003). "1990-1995". Apple II History. Archived from the original on August 19, 2010. Retrieved May 25, 2010.
  11. ↑ "The 25 Greatest PCs of All Time". PC World. Archived from the original on May 11, 2008.
  12. ↑ Rose, Frank (1989). West of Eden. Arrow Books. p. 3. ISBN 0-09-976200-5.
  13. ↑ "June 10, 1977 - Apple II Released Today". This Day in History. Mountain View, CA: Computer History Museum. Archived from the original on June 20, 2012. Retrieved August 3, 2012. June 10, 1977 was a Friday.
  14. ↑ Weyhrich, Steven (December 2008). "4-The Apple II, cont. - Product Introduction". Apple II History. Apple2History.org. Archived from the original on May 22, 2015. Retrieved August 3, 2012. The first motherboard-only Apple II computers shipped on May 10, 1977, for those who wanted to add their own case, keyboard, and power supply (or wanted to update their Apple-1 'system' with the latest and greatest). A month later, on June 10, 1977, Apple began shipping full Apple II systems.
  15. 1 2 3 Helmers, Carl (March 1978). "An Apple to Byte". BYTE. Vol. 3, no. 3. p. 18. Retrieved October 17, 2013.
  16. ↑ Ahl, David H.; Rost, Randi J. (1983). "Blisters And Frustration: Joysticks, Paddles, Buttons and Game Port Extenders for Apple, Atari and VIC". Creative Computing Video & Arcade Games. Vol. 1, no. 1. pp. 106ff. Archived from the original on February 24, 2021. Retrieved January 28, 2021.
  17. ↑ Forster, Winnie (2005). The Encyclopedia of Consoles, Handhelds & Home Computers 1972–2005. Gameplan. p. 19. ISBN 3-00-015359-4.
  18. ↑ 1977 Apple II price list A-VIDD Electronics Co., 1977 Long Beach, CA.
  19. ↑ Weyhrich, Steven (April 21, 2002). "4-The Apple II, cont". Apple II History. Archived from the original on September 25, 2006. Retrieved November 16, 2006.
  20. ↑ Connick, Jack: "...And Then There Was Apple". Call-A.P.P.L.E. Oct 1986: 24.
  21. ↑ Wozniak, Steve (May 1, 2014). "How Steve Wozniak Wrote BASIC for the Original Apple From Scratch". Gizmodo. Archived from the original on May 2, 2014. Retrieved May 2, 2014.
  22. ↑ Williams, Gregg; Moore, Rob (December 1984). "The Apple Story / Part 1: Early History". BYTE (interview). Vol. 9, no. 13. pp. A67. Retrieved October 23, 2013.
  23. ↑ Wozniak, Steve (May 1977). "System Description / The Apple-II". BYTE. Vol. 2, no. 5. pp. 34–43. Retrieved October 17, 2013.
  24. ↑ Gibson, Steve. "The origins of sub-pixel font rendering". Gibson Research Corporation. Archived from the original on July 21, 2006. Retrieved August 4, 2006.
  25. ↑ Weyhrich, Steven (December 28, 2001). "5-The Disk II". Apple II History. Archived from the original on December 1, 2006. Retrieved November 16, 2006.
  26. ↑ Freiberger, Paul; Swaine, Michael (January 1985). Fire In The Valley, Part Two (Book excerpt). p. 45. {{cite book}}: |work= ignored (help)
  27. ↑ Laurel, Brenda; Mountford, S. Joy, eds. (1990). The art of human-computer interface design. Addison-Wesley Pub. Co. ISBN 0-201-51797-3. OCLC 490225229.
  28. ↑ Hyde, Randall (1981). Using 6502 Assembly Language: How Anyone Can Program the Apple II (1st ed.). Datamost. ISBN 9780881900033.
  29. ↑ "An Apple II Manual Sells At Auction For $787,484". NPR.org. Archived from the original on September 4, 2022. Retrieved September 4, 2022.
  30. ↑ "The untold story behind Apple's $13,000 operating system". CNET. San Francisco, CA. Archived from the original on April 4, 2013. Retrieved April 4, 2013.
  31. ↑ "DigiBarn Docs: "How Apple Booted Up" Key Documents in the Creation of Apple's First Operating System (Apple II DOS, 1978)". CA: DigiBarn. Archived from the original on April 3, 2013. Retrieved April 4, 2013.
  32. ↑ "Apple Computer The Early Days A Personal Perspective". Paul Laughton. Archived from the original on July 25, 2013. Retrieved April 4, 2013.
  33. 1 2 Petersen, Marty (February 6, 1984). "Review: Premium Softcard IIe". InfoWorld. Vol. 6, no. 6. pp. 64–66. Archived from the original on March 10, 2023. Retrieved September 20, 2021. Several manufacturers, however, make Z80 coprocessor boards that plug into the Apple II.
  34. ↑ "Школьная информатика в России – техническая база начального периода" (in Russian). Archived from the original on September 23, 2015. Retrieved February 1, 2019.
  35. ↑ Stein, Jesse Adams (2011). "In Memoriam: Domesticity, Gender and the 1977 Apple II Personal Computer". Design and Culture. Vol. 3, no. 2. p. 194.
  36. ↑ Helmers, Carl (April 1977). "A Nybble on the Apple". BYTE. Vol. 2, no. 4. p. 10. Retrieved October 16, 2013.
  37. ↑ Coll, John; Sweeten, Charles (August 1978). "Colour is an Apple II". Personal Computer World. p. 50. Retrieved August 18, 2014.
  38. ↑ Badgnall, Brian. Commodore. ISBN 978-0973864960.
  39. ↑ Malone, Michael S. (1999). Infinite Loop. Doubleday Business. p. 157. ISBN 0-385-48684-7.
  40. ↑ "The 25 Greatest PCs of All Time".
Wikimedia Commons has media related to Apple II.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.