Apple ][ in common 1977 configuration with 9'' monochrome monitor, game paddles, and Red Book recommendedPanasonicRQ-309DS cassette deck
History
By 1976, Steve Jobs had convinced the 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.[5]The earliest Apple II's were assembled inSilicon Valley, and later in Texas;[8]printed circuit boardswere manufactured inIrelandandSingapore. The first computers went on sale on June 10, 1977[9][10]with aMOS Technology 6502microprocessor running at 1.022,727MHz(2⁄7of the NTSC color carrier), twogame paddles[11](bundled until 1980, when they were found to violateFCC regulations),[12]4KiB ofRAM, anaudio cassetteinterface for loading programs and storing data, and theInteger BASICprogramming language built into theROMs.
Dung Beetlessplash screen
Apple II (original)
TheApple II(stylized asapple ][) is an8-bithome computerand one of the world's first highly successful mass-producedmicrocomputerproducts.[2]It was designed primarily bySteve Wozniak;Steve Jobsoversaw the development of the Apple II's foam-molded plastic case[3]andRod Holtdeveloped theswitching power supply.[4]It was introduced by Jobs and Wozniak at the 1977West Coast Computer Faireand marks Apple's first launch of a personal computer aimed at a consumer market—branded toward American households rather than businessmen or computer hobbyists.[5]
Bytemagazine referred to the Apple II,Commodore PET 2001and theTRS-80as the "1977 Trinity."[6]The Apple II had the defining feature of being able to display color graphics, and this was why theApple logowas redesigned to have a spectrum of colors.
The Apple II is the first model in theApple II series, followed by theApple II+,Apple IIe,Apple IIc, and the 16-bitApple IIgs–all of which remained compatible. Production of the last available model, theApple IIe, ceased in November 1993.[7]
Overview
In the May 1977 issue ofByte,Steve Wozniakpublished a detailed description of his design; the article began, "To me, a personal computer should be small, reliable, convenient to use, and inexpensive."[16]
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: occurs only on alternate phases of the clock cycle, the video generation circuitry's 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 separaterefreshcircuit for theDRAMchips, as the video transfer accessed each row of the dynamic memory within thetimeoutperiod. In addition, it did not require separate RAM chips for the video RAM, while the PET and TRS-80 had SRAMs for the video.
- Rather than use a complexanalog-to-digitalcircuit to read the outputs of the game controller, Wozniak used a simple timer circuit whose period is proportional to the resistance of the game controller, and used a software loop to measure the timer.
- A single 14.31818MHz master oscillator (fM) was divided by various ratios to produce all other required frequencies, including the microprocessor clock signals (fM/14), the video transfer counters, and the color-burst samples (fM/4).
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 the 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 the 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 forsubpixelfont rendering, since orange and blue pixels appear half a pixel-width farther to the right on the screen than green and purple pixels.[17]
The Apple II at first useddata cassettestorage like most other microcomputers of the time. In 1978, the company introduced an external 51⁄4-inchfloppy diskdrive, theDisk II, attached via a controller card that plugs into one of the computer'sexpansion slots(usually slot 6). The Disk II interface, created by Wozniak, is regarded as an engineering masterpiece for its economy of electronic components.[18][19]
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.
| Developer | Steve Wozniak(lead designer) |
|---|---|
| Manufacturer | Apple Computer, Inc. |
| Product family | Apple II series |
| Release date | June1977; 43years ago[1] |
| Introductory price | US$1,298(equivalent to $5,476 in 2019) |
| Discontinued | May1979; 41years ago |
| Operating system | Integer BASIC/Apple DOS |
| CPU | MOS Technology 6502 |
| Memory | 4KiB, 8KiB, 12KiB, 16KiB, 20KiB, 24KiB, 32KiB, 36KiB, 48KiB, or 64KiB |
| Storage | Audio cassette, Disk II(5.25-inch, 140KB, Apple) |
| Display | NTSCvideo out (built-inRCA connector) |
| Graphics | Lo-res (40×48, 16-color) Hi-res (280×192, 6-color) |
| Sound | 1-bit speaker (built-in) 1-bit cassette input (built-inmicrophone jack) 1-bit cassette output (built-inheadphone jack) |
| Input | Upper-case keyboard, 52 keys |
| Controller input | Paddles |
| Connectivity | Parallel portcard (Apple and third party);Serial portcard (Apple and third party);SCSI |
| Predecessor | Apple I |
| Successor | Apple II Plus |
Case design
Steve Jobs extensively pushed to give the Apple II a case that looked visually appealing and sellable to people outside of electronics hobbyists, rather than the generic wood and metal boxes typical of early microcomputers. The result was a futuristic-looking molded white plastic case. Jobs also paid close attention to the keyboard design and decided to use dark brown keycaps as it contrasted well with the case.
The first production Apple II's 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. In addition, the initial case design had no vent openings, causing high heat buildup from thePCBand 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'sprinted 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 on the later board revisions. Revision 0 Apple IIs could display only 4 colors in hi-res mode, but Wozniak was able to increase this to 6 hi-res colors on later board revisions.
The PCB had threeRAMbanks for a total of 24 RAM chips. Original Apple IIs had jumper switches to adjust the RAM size, and RAM configurations could be 4, 8, 12, 16, 20, 24, 32, 36, or 48KiB. The three smallest memory configurations used 4kx1DRAMs, 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 earlyApple 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 48KiB complement of DRAM.
Unlike most machines, allintegrated circuitson 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 anIRQ, although expansion cards may generate one. Program code had to stop everything to perform anyI/Otask; 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 theNTSCtelevision 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 thephaseof this signal in relation to a referencecolor burstsignal. The result is that the position, size, and intensity of a series of pulses define color information. These pulses can translate intopixelson the computer screen, with the possibility of exploitingcomposite 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 offset of the pixels 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 8KiB of RAM; in practice this meant that the user had to have at least 12KiB of total RAM to use HGR mode and 20KiB to use two pages. Early Apple II games from the 1977 to 79 period often ran only in text or low resolution mode 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: the cassette output works the same as the speaker, and the input is a simplezero-crossing detectorthat serves as a relatively crude (1-bit) audio digitizer. Routines in the ROM encode and decode data infrequency-shift keyingfor the cassette.
Programming languages
Initially, the Apple II was shipped with Integer BASIC encoded in the motherboardROMchips. 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 createApplesoft BASIC.
Disk users normally purchased a so-called Language Card which had Applesoft in ROM and sat below the Integer BASIC ROM in system memory. The user could switch between either BASIC by typing FP or INT at the 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, the Apple II incorporated amachine code monitorwith 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, and later theUCSDcompiler and operating system for thePascallanguage were made available. The Pascal system requires a 16KiB RAM card to be installed in the language card position (expansion slot 0) in addition to the full 48KiB of motherboard memory.
Manual
The first 1,000 or so Apple IIs shipped in 1977 with a 68-pagemimeographed"Apple II Mini Manual", hand-bound with brass paper fasteners. This was the basis for theApple II Reference Manual,which was 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'sBIOS.
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'sopen-architecturedesign and the Apple II's multiple expansion slots permitted a wide variety of third-party devices, includingperipheral cardssuch asserial controllers, display controllers, memory boards, hard disks, networking components, andrealtime clocks. There were plug-inexpansion cards—such as theZ-80 SoftCard—that permitted the Apple to use theZ80processor and run programs for theCP/Moperating system,[20]including thedBase IIdatabase and theWordStarword processor. The Z80 card also allowed the connection to a modem and thereby to any networks that the 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-party6809card that allowedOS-9Level One to be run. Third-partysound cardsgreatly improved audio capabilities, allowing simple music synthesis and text-to-speech functions.Apple II accelerator cardsdoubled or quadrupled the computer's speed.
Early Apple IIs were often sold with aSup'R'Mod, which allowed the composite video signal to be viewed on a television.
The Soviet Union electronics industry designed Apple II mostly compatible computer Agat 7, producing a similar computer known as theAgat. Roughly 12,000 were produced and it was widely used in Soviet schools.[21]
Reception
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 amachineto anappliance." 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."[22]After seeing a crude,wire-wrappedprototype demonstrated by Wozniak andSteve Jobsin November 1976,[11]Bytepredicted 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.[23]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."[11]
Personal Computer Worldin 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".[24]
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 programVisiCalcwas launched in mid-1979. VisiCalc is credited as the definingkiller appin the microcomputer industry.
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.[25]During this period the sole products of the company were the Apple II and its peripherals, accessories, and software.