Apple II

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Apple II
Apple II
Manufacturer Apple computer
Type Home computers
publication April 1977 (USA)
End of production November 1993 (USA)
Factory price US $ 1298 (approx. DM 3500 to 5000) depending on the equipment
processor 6502 @ 1.022727 MHz
random access memory 4 to 64  kB RAM
graphic 15 colors: 40 × 48 pixels
2 colors: 280 × 192 pixels
Sound nv
Disk 5¼ ″ floppy disks , compact cassettes
operating system Applesoft BASIC , Apple DOS , ProDOS , Apple CP / M , Apple Pascal
predecessor Apple I.
successor Apple II +

The Apple II (also Apple] [ or Apple // ) from Apple Computer is one of the first 8-bit microcomputers to be widely used. Together with its predecessor, the Apple I , it is the last computer in series production that was designed by a single person, namely Steve Wozniak .

When it was launched, the Apple II had eight free slots of the 8-bit Apple bus system with which it could be individually expanded. The Apple II series was an open system , which means that all essential construction details were published. Numerous video games and software for home users existed for the device . At the same time, the computer was also suitable for office applications and other professional use, partly because of its modular and expandable structure. In the literature it is therefore partly counted among the home computers , but also among the early workstation computers .


The Apple II is the successor to the Apple I and was developed by Steve Wozniak and marketed by Steve Jobs (both co-founders of Apple ) from April 1977. Various illegal Apple clones soon appeared , including those made by do-it-yourselfers, as only easily available standard chips were used in the early Apple II models . As with other computer models of this time, commercial clones were mainly produced in East Asia, Brazil and the then communist Eastern Bloc , as the original American computers there were difficult to obtain due to export or import barriers or too expensive compared to the average income. At the same time, legal prosecution of the cloners in these countries was difficult or impossible at the time. Building legal Apple clones was very time-consuming, as Apple did not license the firmware (except for ITT 2020 ), and the development of a compatible, but not identical, firmware in the clean room process was a lot more difficult in contrast to the later IBM PC (because it was still no clean entry table existed). It was not until the mid-1980s that the Laser 128, a largely compatible and at the same time legal clone, came onto the market.

The Apple II series was built from 1977 to 1993, about 16 years. Over two million original Apple II computers have been manufactured during that time. The countless replicas of this series are not included in this number.

The main reason why the series was so successful was that the computer was an open system . In the early models, all circuits and signals as well as the firmware were documented in publications available to everyone, in the later models there were some ASICs whose exact content was not published, but their essential functions were also no secret. You could buy a wide variety of cards for the slots of the Apple II or build them yourself. There were memory expansion cards, various interface cards (e.g. for printers, modems, floppy and hard disk drives), control cards (e.g. for Fischertechnik construction kits, but also I / O cards for industry and research), graphics cards, sound cards, real-time clocks, and even processor cards with other processors like Z80 or 68000 .

The software for the Apple was mostly more innovative than the competition. The Visicalc program was the first spreadsheet program for microcomputers. The AppleWorks program was the first to combine a word processor, a spreadsheet and a database in one program.

The Apple II was one of the first three successful microcomputers (together with the Commodore PET 2001 and Tandy TRS-80, which were presented at the same time ) that were not sold as a kit but as a finished device. At the time, it was common for the buyer to at least have to find a suitable keyboard and monitor himself, and sometimes only bare circuit boards without power supply unit and housing were sold as computers (like the first Apple model, the Apple I ).

The Apple II was often cloned due to its widespread use - not just outside the US . The list of Apple II clones provides an incomplete list of these clones .


Inner workings of the Apple II

An 8-bit 6502 CPU with a clock frequency of 1.022 7 2 7  MHz was used in the Apple II . In the basic version it had 4 kB RAM, expandable up to 64 kB, in the later models up to 16 MB.


A typewriter keyboard, almost without special keys, was built in. With the first Apple II, you could only enter capital letters - according to the Apple II developer Steve Wozniak , the only keyboard he could afford at the time was one with capital letters.

Text mode

The original Apple II was only able to use the ASCII character set without lowercase letters (64 printable characters and 32 control characters) for output in text mode . In text mode, the Apple displayed 24 lines of 40 characters each. The characters were 5 × 7 points in size and written in 7 × 8 point character boxes. Only white text on a black background was possible, the color capability of the Apple only came into play in graphics mode. Each character could be displayed as normal, negative or flashing (quickly changing between normal and negative). In contrast to some other home computers, the character set could not be changed using software. Lowercase letters, umlauts and graphic characters were therefore only possible using hardware hobbyist solutions (patched EPROMs , which were widespread among Apple II users in Germany at the time). However, some clones, for example the base 108 , had alternative character sets ex works. It was not until the Apple IIe that lowercase letters and in its German version also umlauts were able to be used - but only in exchange for rarely used other characters of the ASCII character set, in accordance with the then current ISO 646 standard . There was a switch on the underside of the device with which you could choose between ASCII and GSCII ("German ASCII").


Color palette of the Apple II
Screenshot from the first graphic adventure Mystery House (Hi-Res with four colors)

The core of the Apple II design was a digital graphics and character generator ; this was incorporated into the system in such a way that it also refreshed the DRAM memory. The graphic had a special address space in the main memory. In addition to the text mode possible with any memory size and the coarse “LoRes” color graphics (40 × 48 in 15 colors), the Apple II offered a high-resolution “HiRes” graphics mode with 280 × 192 pixels from a memory expansion of 16 kB ; The background (unset pixels) was always black, individual set pixels appeared on a color monitor, depending on whether they were in even or odd columns, in two different colors, two or more pixels set next to each other always white. For every seven pixels there was also the option to switch between two color spaces. This enabled the Apple II to display high-resolution graphics in six colors (black, white, green, purple, orange, turquoise blue), which was revolutionary in 1977. In addition, switching to the second color space resulted in a horizontal shift by half a pixel width, which could be used to expand the horizontal resolution with skilful programming.

A video monitor was used as the display or a television set via an interposed HF modulator (today's televisions can be connected directly via the video or SCART input, but models at that time almost always only had an antenna socket, which required a modulated HF signal) . The color output only worked with the American NTSC television system, as it made use of its special properties in order to enable color graphics with so few chips. A major factor in color generation was the use of 14.318 MHz as the primary clock in the Apple II - that's four times the NTSC color subcarrier frequency. This made it possible to easily generate the amplitude-modulated chrominance signals.

Since the same clock (divided by 7 or 14) also served as the bit clock for the floppy disk drive and for the entire system timing, it could not simply be replaced in the European Apples by a multiple of the PAL color subcarrier frequency, otherwise floppy disks would no longer be were compatible between the two model variants and programs would have been executed at different speeds. In the European Apples, a PAL color card was therefore required that received the pseudo-NTSC signal from the motherboard and converted it to PAL. From the European IIe this was integrated on the motherboard. The pseudo-NTSC signal is generated by a different crystal oscillator than the PAL color carrier. Since crystal oscillators always have minimal frequency fluctuations, the independent fluctuation of the two oscillators inevitably results in an irregular frequency overlay ( beat ) in this arrangement . As a result, the color video image of European apples is restless; it tends to jitter the image and to move up or down moiré patterns. However, text mode is not affected by this problem.

Apple II with floppy disk drives

Storage media

The most common storage medium was 5¼ inch floppy disks . Steve Wozniak had considered the floppy disk drives available at the time to be too expensive and ineffective and developed his own control electronics which, by letting the computer CPU do much of the coding and timing, were actually cheaper and could store more data per disk than competing products. Typical disk drives at that time had a capacity of 80–90 kB, Wozniak managed over 110 kB with the same drive mechanism, and in a second version even 140 kB per disk side. The design of the drive controller was so effective that Apple later used it as a single-chip solution under the name Integrated Woz Machine in Apple II successors and also in Macintosh computers.

When using floppy disks, the operating system was usually Apple DOS or later ProDOS in addition to the built-in Applesoft BASIC (or before II + Integer BASIC ) . There were also a number of faster DOS operating systems from third-party manufacturers, e. B. Diversi-DOS. The Hüthig-Verlag published a Unix version called KIX. In contrast, the UCSD - Pascal version, Apple Pascal, was widely used as the operating system in schools and universities ; Based on this, there was also the Modula-2 programming language . Saving to tape cassettes was possible, but only common with the Apples in the very early days, before a floppy disk drive became available in 1978. The cassette retained a certain importance as a medium for backup copies, since an inexpensive C90 cassette could store the contents of several floppy disks and floppy disks were very expensive in the early 1980s (approx. 5 DM).

From 1983 hard disks were even available with capacities of 10 and 20 MB, which were enormous for the time. The company Frank & Britting GmbH, Forst (Baden) (no longer existent) offered the first hard drives from the Scottish manufacturer Rodime with their controllers for the Apple with a micro Winchester (3.5 inch) with 10 MB capacity. The data was accessed with an average of 93 milliseconds. DOS, CP / M, UCSD-Pascal and ProDOS could be accommodated simultaneously in four partitions on the hard disk. After starting a menu was responsible for the selection.

The Compu-Shack company (also defunct) sold this installation kit that replaced the power supply unit. The selling price for 20 MB was 4560 DM at the start of sales, for the 10 MB version 3990 DM.


Power supply unit, next to it the expansion cards: 16 kB memory expansion (“ Apple II Language Card ”), card with a Z80 processor, 80-character card and card for floppy disk drives

The Apple II had an expansion bus with eight slots, which Steve Wozniak had enforced against the will of Steve Jobs. Since Wozniak had openly documented these slots and the entire design, a wealth of additional cards were created, for example the Microsoft Softcard expansion card with a Z80 processor, so that the computer could be operated with the Apple CP / M operating system and the standard office software available for it at that time, such as WordStar and dBASE .

Other popular extensions were: a memory extension of 16 kB called “ Apple II Language Card ”, which could replace the built-in ROM address space with a reloadable language interpreter; 80-character cards, which doubled the number of characters that can be displayed per line (the “Videx VideoTerm” card and its various replicas were particularly popular; 80-character cards were available as standard from the IIe as soon as a memory expansion card was inserted), serial and parallel interface cards for printers and external modems or acoustic couplers . In addition, there were the first, simple sound cards like the mocking board , which were clearly superior to the built-in loudspeaker of the Apple, but were only supported by a few programs. The mocking board contained u. a. the sound chip AY-3-8910 from General Instrument , which was almost identical to that of the Atari ST and the MSX computer, which was very successful in Japan .

Expansion card for floppy disk drives

In addition, there were also expansion cards with which it was possible to connect floppy disk drives or even the first hard drives to the Apple II. There were also internal modems.

The expansion card concept was so successful that IBM later adopted it for the first PC. However, the slot concept of the IBM PC represented a clear step backwards compared to the Apple II. Expansion cards for the Apple II could bring their driver software on the board and were given a fixed (memory) address through the slot. This made it possible with many cards to simply plug them into a free slot and use them without any further installation work. On the other hand, the expansion cards on the IBM PC had to have their addresses set using DIP switches, which led to problems if two cards were given the same address. In addition, it was necessary to install the driver software on the IBM PC.

Game port

Apple 2 paddles

You could already connect two paddles or an analog joystick to the original Apple II ; a primitive analog-to-digital converter was integrated (the method was copied from the game port of the IBM PC and was in use for a long time, but was superseded by USB ). The joystick could also be incorporated into your own programs relatively easily and used for input.

The game port had four inputs for a potentiometer with 150 kΩ each , three inputs for buttons and five digital outputs, four of which were switchable, and one that could only output short pulses. The intended connection for the game port, and even more so the plug to be used there, were mechanically not particularly stable. The connection was an IC socket in DIL16 format inside the computer; To plug something in there, the computer had to be opened, the cable was then led out of the case through an opening on the back. On the Apple IIe, this connection was supplemented by an externally attached 9-pin D-Sub socket, on which the digital outputs were no longer brought out. The later models only had the D-Sub socket, the internal connection was omitted.

It is interesting that the three inputs for buttons came about because the module used for the buttons and axes had eight inputs, one of which was used to implement the cassette input. The axes were implemented by four monoflops , the switching time of which was determined by the set resistance of the potentiometer, leaving three inputs for buttons.


The Apple II possessed innately non- timers (timer) and interruptions ( interrupts ). Wozniak cited the reason that he wanted to keep the design as simple as possible. In addition, an interrupt-driven keyboard driver had failed, so that it used a " polling " method for it.

Because of the missing timer interrupt, z. For example, the precise playback of music via the built-in loudspeaker is very complex; the length of each individual machine code command had to be calculated in order to switch the loudspeaker on and off at the correct frequency. Since some 6502 commands required different numbers of cycles depending on the register contents, this was not trivial.

The code for the floppy disk drive driver was also stopped for the exact cycle; By handling time-critical functions in software, Wozniak was able to build a groundbreaking, simple and flexible floppy disk drive. The bootloader in a PROM on the floppy disk drive plug-in card, which could autonomously reload a complete DOS from the floppy disk, was only 252 bytes in size , including the GCR code table.

Additional cards such as the aforementioned “Mockingboard” sound card retrofitted the missing timer interrupts, mostly based on the “Versatile Interface Adapter” chip 6522 , which has now been released and which also found its way into the Apple III design.

Further development of the master model

Apple II logo

The original model was further developed in 1979 into the Apple II + and Apple II europlus ; the latter was the first microcomputer to be sold on a large scale in Europe. The II + always offered 48 kB of memory (the smaller expansion variants were no longer supported) and came with a different firmware : unlike the Apple II, whose ROM still contained the Apple Integer Basic developed by Steve Wozniak , it offered Applesoft BASIC , that of Microsoft originated. It was noticeably slower, used more memory and was less clear in structure than Integer BASIC, but had the great advantage that, in contrast to this, it could also calculate with floating point numbers . Apple's own expansion of Integer BASIC in this direction had failed due to lack of time, which is why the decision was made to purchase. Applesoft BASIC has commands for displaying high-resolution color graphics, otherwise it is largely identical to the Commodore BASIC e.g. B. the Commodore 64 , because this also came from Microsoft and originated from the same code base . The only difference between the Europlus and the II + was the adaptation to the European television standard with its 50 frames per second instead of 60 as in America. The Europlus keyboard and character set remained American, but hobbyists and resellers often made adjustments.

The market

In 1980 the Apple II mutated into the less successful Apple III (whose failure on the IBM market with their IBM PC , which, like the Apple II, had an open architecture, opened up a large market niche), was then further developed into the IIe in 1982 and the portable IIc in 1984 Ultimately replaced in 1986 by the II GS equipped with the 65C816 processor and partly working with 16 bit , which was hardly advertised by Apple and, alongside the Apple Macintosh computers, the Atari ST and the Commodore Amiga , received little attention in Europe. A successor with the code name "Apple // x" or "Golden Gate" conceived in 1984/1985 with the collaboration of Steve Wozniak did not come out of an early stage of development. The computer based on the WD 65816 CPU should be. a. expandable with a 68000 processor, compatibility with Apple Macintosh or a graphical user interface were not intended at this time.

Since the Apples were very popular and widespread in American schools, the series continued for a few years. After two ROM revisions, the Apple IIgs was discontinued in November 1992. A third ROM revision, codenamed "Mark Twain" only reached prototype status; In contrast to the serial device, this computer would also have an integrated hard disk, an integrated 3.5-inch floppy disk drive and a SCSI interface.

After production of the Apple IIg ended, the Apple IIe was manufactured until 1993.

Computer games

Apple II with the game Ali Baba and the Forty Thieves on an amber monitor

In the USA the Apple II also determined the early mailbox scene and a great many computer games appeared for the Apples; in Western Europe , on the other hand, other systems that appeared later - such as the Commodore C64 - dominated the games market. Mailboxes only became popular in Germany later because of the higher telephone charges and the extremely restrictive modem policy of the Bundespost at the time . The first four computer games (ROCKET PILOT, STAR WARS, SAUCER INVASION, SPACE MAZE) for the Apple II were developed by Bob Bishop .

Some well-known classics first appeared on the Apple II. Many of them were later ported to other common home computers such as the C64 or the PC, including Akalabeth , Ultima , Wizardry , Choplifter , Prince of Persia , Castle Wolfenstein and The Bard's Tale . In particular, the first graphic adventure Mystery House appeared exclusively . The Oregon Trail was first ported from the mainframe to the Apple II. On the other hand, many well-known arcade games appeared here , including Defender , Frogger , Dig Dug , Battlezone or games from other home computers, such as California Games and The Last Ninja .

Source code publication

In 2013, 35 years after the Apple came on the market II, the associated was Apple DOS - source code from the Computer History Museum published on its website. Paul Laughton, the programmer, had made it available.


  • Winston D. Gayler: Apple II Schematics . Pandabooks, Berlin 1984, ISBN 3-89058-012-2
  • Erich Esders: The book on APPLE II. Working with the APPLE II and IIe computers . Franzis Verlag, Munich 1988, ISBN 3-7723-7641-X
  • Steven Weyhrich: Sophistication & Simplicity. The Life and Times of the Apple II . Variant Press, ISBN 0-986-83227-8

Web links

Commons : Apple II  - collection of pictures, videos and audio files

Individual evidence

  1. The dream of the simple computer In: Der Tagesspiegel
  2. Len Shustek: Apple II DOS source code ( English ) November 12, 2013. Retrieved November 30, 2013.
  3. Matt Brian: Apple II's 35-year-old operating system is now open to the public ( English ) November 13, 2013. Retrieved November 30, 2013.