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1980s Computers Explanation of terms

The Commodore PET

PET 2001-4


Commodore (US)


PET 2001
(Personal Electronic Transactor)
Later called the 4000 series.

Date Launched

January 1977
(But first production models did not appear until June 1977.)


From £650
UK prices in May 1979 were: PET 2001/4 £539, PET 2001/8 £594, PET 2001/16N £729.

Microprocessor type

MOSTEK 6502 @ 1 MHz
(Commodore owned the maker of the 6502 at this time)

ROM size

14 kilobytes
(8KB BASIC, 4KB operating system, 1KB diagnostics, 1KB machine language monitor)

Standard RAM

4 kilobytes (2001-4)
8 kilobytes (2001-8)
16 kilobytes (2001-16N)
32 kilobytes (2001-32N)

Maximum RAM

32 kilobytes

Keyboard type

The early PET 2001s (see picture above) had a cramped, calculator-like keyboard on which the markings tended to wear off:

Early PET keyboard

Later models as shown below had a good typewriter style keyboard.

Supplied language

Microsoft BASIC (written by Bill Gates).
Pascal, FORTH, COMAL, LISP and Pilot could also be used.

Text resolution

40 x 25 characters
Later 80 x 25 in the CBM 8032 of 1980.

Graphics resolution

No graphics but had many specialised symbols in its character set.

Colours available



Through internal speaker

Cassette load speed

1000 baud but programs were recorded twice and checked against each other to detect errors, reducing the effective speed to 500 baud.

The small-keyboard PET 2001-4 and 2001-8 had a cassette deck built into the case at the side of the keyboard.

New style PETWhen full size keyboards were introduced (see picture right) with the 2001-16N and 2001-32N models, the cassette recorder had to become a separate item.

Dimensions (mm)
Weight (grams)

420 x 470 x 350
20000 with integral monitor

Special features

A self-contained unit including the 9 inch display.
Incorporated an IEEE-488 bus which at the time was widely used for interfacing to scientific equipment.

Good points

One of the first desktop computers that could just be plugged in and used straightaway, without any assembly.
A considerable library of software was developed.
Good quality of construction.

Bad points

A little expensive for the home market (though cheap as a business computer) and the lack of colour and graphics counted against it.
It was not possible to type lower-case letters directly from the keyboard. instead a command 'POKE 59468,14' had to be issued first, but this disabled the specialized graphics characters. 'POKE 59468,12' swapped back to upper-case only plus graphics.

How successful?

Popular with small businesses, schools and public services because it needed little in the way of setting up and was robust, with a metal case.
Over 40,000 were sold in the UK alone.


The Commodore PET, with updates giving it more memory, a better BASIC and more streamlined styling, remained on sale until the early 1980s.
Commodore wanted to replace it sooner with the '64' model, but this was purely a home games machine and not what businesses or schools wanted.

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