Commodore VIC-20

From Academic Kids

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VIC-20 with accessories.

The VIC-20 was an 8-bit home computer made by Commodore Business Machines with 5 KB RAM and a MOS 6502 CPU, similar in physical shape to the later Commodore 64 and C16. The VIC-20 was released in June 1980, 2¾ years after Commodore's first personal computer, the PET.



The VIC-20 was intended to be more of a low-end home computer than the PET. Reportedly, the VIC-20's video chip was intended for use in inexpensive display terminals and game consoles, but Commodore couldn't find a market for the chip. At the same time, Commodore had an oversupply of 1Kbit×4 SRAM chips. In April 1980, Commodore president Jack Tramiel ordered the development of a computer that could sell for under $300 US. What had been an oversupply of parts became the VIC-20. While the PET was sold through authorized dealers, the VIC-20 primarily sold at retail, especially discount and toy stores, where it could compete more directly with game consoles. Commodore took out advertisements featuring actor William Shatner of Star Trek fame as its spokesman, asking, "Why buy just a video game?".

Although the VIC-20 was criticized in print as being underpowered, the strategy worked: it became the first computer to sell more than 1 million units and was the best-selling computer of 1982. At its peak, 9,000 units per day were produced, and a total of 2.5 million units were sold before it was discontinued in January 1985, when Commodore repositioned the C64 as its entry-level computer due to the forthcoming release of the C128 and Amiga (the latter taking Commodore into the 16-bit world).

Because of its small memory and low-resolution display compared to some other computers of the time, the VIC-20 was primarily used for educational software and games. However, productivity applications such as home finance programs, spreadsheets, and communication terminal programs were also made for the machine. Its high accessibility to the general public meant that quite a few software developers-to-be cut their teeth on the VIC-20, being introduced to BASIC programming, and in some cases going further to learn assembly or machine language. Several magazines, such as Compute!, sold on newsstands offered type-in programs for the VIC-20, including one published by Commodore itself. Many VIC users learned to program by entering, studying, running, and modifying these type-ins.

The ease of programming the VIC and availability of an inexpensive modem combined to give the VIC a sizeable library of public domain and freeware software, although much smaller than that of the C64. This software was distributed on online services such as CompuServe, BBSs, and via user groups.

As for commercial software offerings, an estimated 300 titles were available on cartridge, and another 500+ titles were available on tape. By comparison, the Atari 2600, the most popular of the video game consoles at the time, had a library of about 900 titles.


The VIC-20 had proprietary connectors for program/expansion cartridges and a tape drive (PET 'Datassette'). It came with 5 KB RAM, but 1.5 KB were used by the system for various things, like the video display (which had a rather unusual 22×23 char/line screen layout), and other dynamic aspects of the ROM-resident BASIC interpreter and KERNAL (a low-level operating system). Thus, 3.5 KB of BASIC program memory for code and variables was available to the user of an unexpanded machine. The VIC-20 also had a serial bus (a serial version of the PET's IEEE-488 bus) for daisy chaining disk drives and printers; a TTL-level "user port" with RS-232 and Centronics signals (most frequently used as RS-232, for connecting a modem); and a single DE-9 joystick port, compatible with the joysticks used with Atari videogame consoles and, later, the C64.

The VIC-20's RAM was expandable with plug-in cartridges using the same expansion port as programs. Port expander boxes were available from Commodore and other vendors to allow more than one cartridge to be connected at a time. RAM cartridges were available in several sizes: 3K (with or without an included BASIC extension ROM), 8K, 16K or 32K; the latter only from third-party vendors. The internal memory map was reorganised with the addition of each size cartridge, leading to the situation that some programs would only work if the right amount of memory was present (to cater for this, the 32K cartridges had switches to allow the RAM to be enabled in user-selected sections). The most visible part of memory that was reorganised with differing expansion memory configurations was the video memory (with text and/or graphics display data).

VIC trivia

  • The name "VIC" came from the Video Interface Chip, which, despite its designation, also handled all the sound synthesis in the VIC-20. The VIC chip's successor, the graphics-and-RAM-refresh VIC-II, was used to great success in Commodore's later best-selling machine, the C64, and also in the dual video output C128 for that computer's 40-column/composite video graphics.
  • The VIC-20 was originally meant to be called Vixen, but this name was inappropriate in Germany, Commodore's second most important market, because it sounds like wichsen, the German language word for "masturbate". VIC, which was subsequently chosen, has a similar problem—it can be pronounced like ficken, the German word for "fuck". Therefore the VIC-20 was finally marketed as the VC-20 "Volkscomputer" in German-language countries—an obvious pun on "Volkswagen".
  • In Japan the VIC-20 was marketed as the VIC-1001 (1980).
  • BASIC programs running on a fully expanded VIC-20 could use at most 24K RAM. Any extra occupied the memory space used by ROM cartridges, i.e. commercial software like games and other applications. This allowed people to copy cartridges to tape and distribute them to their friends, who could then load the tape into the top 8K of their 32K RAM packs.
  • An anecdotal bit of evidence to support Commodore's statement that the VIC-20 could be used not only for games but also as a serious introduction to computing, can be said to originate in the fact that a young Finn called Linus Torvalds was given a VIC-20 as his first computer. Keen to learn more, Torvalds later upgraded to a Sinclair QL, then to a 386 PC, and the rest, as they say, is history...
  • In the e-comic Hackles, the character Hackles assembles a robot based on the VIC-20. The robot was intended to be a Battlebot, but unfortunately Hackles was low on cash when buying the parts.

External links

See also


  • Finkel, A.; Harris, N.; Higginbottom, P.; Tomczyk, M. (1982). VIC 20 Programmer's reference guide. Commodore Business Machines, Inc. and Howard W. Sams & Co, Inc. ISBN 0-672-21948-4.
  • Jones, A. J.; Coley, E. A.; Cole, D. G. J. (1983). Mastering the VIC-20. Chichester, UK: Ellis Horwood Ltd. and John Wiley & Sons, Inc. ISBN 0-471-88892-3.
  • Tomczyk, Michael (1984). The Home Computer Wars: An Insider's Account of Commodore and Jack Tramiel. COMPUTE! Publications, Inc. ISBN 0-942386-75-2.

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.


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