page_title: Commodore PET
section_title: Release
hierarchical_section_title: Commodore PET / History / Release
caption_attribution_description: English: The three computers referred to by Byte Magazine as the "1977 Trinity": The Apple II, the TRS-80 Model I, and the Commodore PET 2001. (Image courtesy of Boston-based collector Timothy Colegrove. For more information about this image send an email to timothy.colegrove@gmail.com)
context_page_description: The Commodore PET is a line of home/personal computers produced starting in 1977 by Commodore International. The system combined a MOS 6502 microprocessor, Commodore BASIC in read only memory, a keyboard, a computer monitor and a cassette deck for data and program storage in a single all-in-one case.
  Development of the system began in 1976 and a prototype was demonstrated in January 1977 at the Consumer Electronics Show. A series of problems meant that production versions did not begin to arrive until December 1977, by which time the TRS-80 and Apple II had already begun deliveries. The close release dates of the three machines led Byte to refer to them collectively as the "1977 trinity".
  The original PET design underwent a series of significant updates, adding more memory, a better keyboard, larger screens and other modifications. The systems were a top-seller in the Canadian and United States educational markets, as well as European business uses. The PET formed the basis for Commodore's entire 8-bit product line, including the Commodore 64.
  The name was suggested by Andre Souson after he saw the Pet Rock in Los Gatos, and stated they were going to make the "pet computer".
context_section_description: The Commodore PET was officially announced in 1976 and Jack Tramiel gave Chuck Peddle six months to have the computer ready for the January 1977 Consumer Electronics Show, with his team including John Feagans, Bill Seiler, two Japanese engineers named Fujiyama and Aoji, and Jack's son Leonard Tramiel who helped design the PETSCII graphic characters and acted as quality control. 
  The result was Commodore's first mass-market personal computer, the PET, the first model of which was the PET 2001. Its 6502 processor controlled the screen, keyboard, cassette tape recorders and any peripherals connected to one of the computer's several expansion ports.  The PET 2001 included either 4 KB (2001-4) or 8 KB (2001-8) of 8-bit RAM, and was essentially a single-board computer with discrete logic driving a small built-in monochrome monitor with 40×25 character graphics, enclosed in a sheet metal case that reflected Commodore's background as a manufacturer of office equipment. The machine also included a built-in Datasette for data storage located on the front of the case, which left little room for the keyboard. The data transfer rate to cassette tape was 1500 baud, but the data was recorded to tape twice for safety, giving an effective rate of 750 baud.  The computer's main board carried four expansion ports: extra memory, a second cassette tape recorder interface, a parallel ("user") port which could be used for sound output or connection to "user" projects or non-Commodore devices and a parallel IEEE-488 port which allowed for daisy-chaining peripherals such as disk drives and printers.
  A working PET 2001 prototype with wooden case was shown to the public at the Winter CES 1977  in January 1977 and the first 100 units were shipped in October, mostly going to magazines and software developers, while the machine was not generally available to consumers until December. However, the PET was back-ordered for months and to ease deliveries, early in 1978 Commodore decided to cancel the 4 KB version (also because the user would be left with barely 3 KB of RAM).
  Dan Fylstra of Byte Magazine received one of the initial PETs in October 1977, S/N 16, and reported on the computer in the March 1978 issue. Fylstra praised its full-featured BASIC, lowercase letters, and reliable cassette system, while disapproving of the keyboard. His machine had three faulty RAM chips and after some difficulty contacting Commodore, was mailed a set of replacement chips and installation instructions by John Feagans.
  Commodore was the first company to license Microsoft's 6502 BASIC, but the agreement nearly drove Microsoft into receivership as Commodore stipulated that they would only pay for it when the PET began shipping. This was delayed by over six months, during which Microsoft lost money and had their cash reserves further depleted by a lawsuit over ownership of Altair BASIC. At the end of the year, Microsoft was saved by Apple's decision to license Microsoft BASIC for the Apple II line.
  The BASIC included on the original PET 2001 was known as Commodore BASIC 1.0; Microsoft supplied Commodore with a source listing for their 6502 BASIC, essentially a port of BASIC-80, and Commodore performed the rest of the work themselves, including changing the startup screen and prompts, adding I/O support, the SYS command for invoking machine language programs, and fixing bugs. BASIC 1.0 still had numerous bugs and IEEE-488 support was broken, so that when Commodore later came out with disk drives, they could not be used from BASIC (although the kernel routines supported them), and only supported 256 array elements. The PEEK function would not work on memory locations above 49152 so as to prevent the user from viewing the copyrighted code in the system ROMs.
  Aside from the 8k BASIC ROM, the PET also included a 4k character ROM and an 8k kernal ROM. The first half of the kernal contained screen editor functions (the screen editor on 80 column PETs differed from 40-column models) with the second half containing a number of function calls for tasks such as inputting and output
caption: The Commodore PET 2001-8 alongside its rivals: The Apple II and the TRS-80 Model I
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