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Commodore VIC-20

The VIC-20 was a home computer made by Commodore Business Machines with 5 KB RAM and a 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.

Table of contents
1 History
2 Description
3 VIC Trivia
4 External links
5 References


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 1K RAM 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 much 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. 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 game consoles, 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 OS (KERNAL). 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 DB-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

External links


This article (or an earlier version of it) contains material from
FOLDOC, used with permission.