Apple II
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.[3] It has an 8-bit microprocessor.
"Apple 2" redirects here. For the nuclear test during Operation Teapot, see Apple-2.Developer
Steve Wozniak (lead designer)
June 1977[1]
US$1,298 (equivalent to $6,530 in 2023)
May 1979
MOS Technology 6502
@ 1.023 MHz
4, 8, 12, 16, 20, 24, 32, 36, 48, or 64 KiB
Audio cassette,
Disk II (5.25-inch, 140 KB, Apple)
NTSC video out (built-in RCA connector)
Lo-res: 40×48, 16-color
Hi-res: 280×192, 8-color[2]
1-bit speaker (built-in)
1-bit cassette input (built-in microphone jack)
1-bit cassette output (built-in headphone jack)
Upper-case keyboard, 52 keys
Parallel port card (Apple and third party); Serial port card (Apple and third party); SCSI
The Apple II was designed primarily by Steve Wozniak; Jerry Manock developed the design of Apple II's foam-molded plastic case,[4] Rod Holt developed the switching power supply,[5] while Steve Jobs was not involved in the design or development of the computer.[6] 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.[7]
Byte magazine referred to the Apple II, Commodore PET 2001, and TRS-80 as the "1977 Trinity".[8] 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.[9][10]
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.[11]
The Apple II is widely regarded as one of the most important personal computers of all time due to its role in popularizing home computing and influencing later software development.[12][13][14][15]
History[edit]
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.[7] The earliest Apple II computers were assembled in Silicon Valley and later in Texas;[16] printed circuit boards were manufactured in Ireland and Singapore. The first computers went on sale on June 10, 1977[17][18] with an MOS Technology 6502 microprocessor running at 1.023 MHz (2⁄7 of the NTSC color subcarrier), two game paddles[19] (bundled until 1980, when they were found to violate FCC regulations),[20] 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 video 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 $6,530 in 2023)[21] and with the maximum 48 KiB of RAM, it was US$2,638 (equivalent to $13,260 in 2023)[22] To reflect the computer's color graphics capability, the Apple logo on the casing has rainbow stripes,[23] 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.[7]
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".[24] 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.[25] 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."[26]
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."[27]
The Apple II used peculiar engineering shortcuts to save hardware and reduce costs, such as:
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.[28]
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.[29][30]
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[edit]
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.[31] 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[edit]
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. (Technically it was eight, but only six was visible.[32])
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.
Sound[edit]
Rather than a dedicated sound-synthesis chip, the Apple II contains a toggle circuit that can only emit a click through a built-in speaker or a line-out jack. More complex sounds, such as music or audio samples, are generated by software manually toggling the speaker at an appropriate frequency. This technique requires careful and precise timing, rendering it difficult to display moving graphics while sound is playing. Third party expansion cards were later released which addressed this problem.
A similar technique is used for cassette storage: cassette output works the same as the speaker, and input uses a simple zero-crossing detector as a 1-bit audio digitizer. Routines in machine ROM encode and decode data in frequency-shift keying for the cassette.
Manual[edit]
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.[34]
Operating system[edit]
The original Apple II came with an 8 KiB ROM containing a BASIC variant called Integer BASIC as well as a resident monitor called the Apple System Monitor. Initially, only cassette tape was available for storage, which was considered too slow and unreliable for business use. In late 1977, Apple began to develop the Disk II floppy disk drive and required an operating system to utilize it. The existing standard at the time was CP/M, but due to incompatibility with the 6502 processor and a perceived clunkiness, Apple contracted Shepardson Microsystems for $13,000 to write Apple DOS.[35][36] At Shepardson, Paul Laughton developed the software in just 35 days, a remarkably short deadline, even for the time.[37] The Disk II and Apple DOS were released in late 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,[38] 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, such as the ability to use floating point numbers.
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[edit]
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,[38] 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.[39] 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.
In 1978, Bob Bishop of Apple Computer, Inc. programmed 9 Apple II computers to run the gameboard on the TV game show Tic-Tac-Dough;[40] each Apple was responsible for displaying a single box of the gameboard, in turn controlled by an Altair 8800 system. It was the first game show to use computerized graphics.[41]