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1980s Computers Explanation of terms

The ZX Spectrum

ZX Spectrum


Sinclair Research Ltd (UK)


ZX Spectrum
(Because of its colour display. The name Rainbow was also considered.)

Date Launched

April 1982


£125 with 16KB RAM.
£175 with 48KB RAM.
Reduced in mid 1983 to £100 and £130.

Microprocessor type

Zilog Z80A (or clone) @ 3.5 MHz

ROM size

16 kilobytes

Standard RAM

16 or 48 kilobytes

Maximum RAM

48 kilobytes

Keyboard type

One-piece rubber mat pressing onto a touch-sensitive membrane.

Supplied language

Sinclair BASIC - slightly idiosyncratic but contained commands to use the graphics and sound.

Text resolution

32 x 24 characters

Graphics resolution

256 x 192 pixels.

Colours available

8, each at two brightness levels, but limited to two different colours in each character square.

Example Screenshot

Spectrum display
The ZX Spectrum allowed easy mixing of text with graphics, and the 'character attribute' system meant colourful displays could be produced if they were carefully designed so that each character square only used two different colours.


Single note beeps through small internal speaker.

Cassette load speed

1500 baud

Dimensions (mm)
Weight (grams)

233 x 144 x 30

Special features

Single key entry of BASIC commands.
Syntax checking of lines as soon as they were entered.
Striking appearance and compact size. It was possible to buy a fitted briefcase to hold a Spectrum and its accessories to provide a very cheap 'portable' computer (provided there was a television available where you needed to use it.)
Briefcase for Spectrum

Good points

A reasonable version of BASIC for the time.
Large memory for 1982.
A huge range of software soon became available. (The Spectrum had many similarities to the established ZX81.)
Could mix text and graphics on the same screen.
Cassette storage was quite fast and mostly reliable.
Had an almost standard ASCII upper- and lower-case character set.

Bad points

Keyboard was poor. This at least provided business for companies supplying replacement keyboards.
No built-in connection for a standard printer.
BASIC was quite slow.
Sound was weak and monophonic.

How successful?

The best selling British-designed home computer. In the first quarter of 1984 Sinclair Research had 43% of the UK home computer market.
Including later enhanced versions over 3 million Spectrums were sold.


The first affordable colour computer.
The combination of reasonable graphics and a large memory meant that some impressive games could be produced, such as 'Lords of Midnight' from Beyond Software, illustrated below:
Lords of Midnight

In October 1984 Sinclair produced the Spectrum Plus which was identical electronically but had a moderate quality moving key keyboard:
Spectrum Plus

Versions of the Spectrum were also made abroad. Czerweny of Argentina sold the CZ-2000 which used an imported standard Spectrum keyboard and motherboard in a slightly modified case and with a TV output to match the local system. In 1986 it was replaced by the CZ-Spectrum, again built under licence but adding a reset button, composite video output and two joystick ports.
Several (almost certainly unlicenced) clones of the Spectrum originated in Russia. Probably the best was the Hobbit made by InterCompex around 1990, which had a full keyboard including numeric pad, 'shadow ROM' facility to allow alternative languages, switchable cyrillic alphabet, ability to run a form of CP/M and optional floppy disk drive. In fact some people might say it was the computer which Sinclair themselves should have brought out instead of the QL.

Review of the ZX Spectrum

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