ZX81

Sinclair ZX81ZX-81Sinclair ZX-81Sinclair ZX81 16KB RAM
The ZX81 is a home computer that was produced by Sinclair Research and manufactured in Dundee, Scotland by Timex Corporation.wikipedia
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Rick Dickinson

Its distinctive case and keyboard brought designer Rick Dickinson a Design Council award.
Notable examples of his design work include the ZX81 case and touch-sensitive keyboard and the ZX Spectrum rubber keyboard.

Timex Sinclair 1000

TS1000TS1500Timex 1000
Timex later produced its own versions of the ZX81 for the US market: the Timex Sinclair 1000 and Timex Sinclair 1500.
The TS1000 was a slightly-modified version of the Sinclair ZX81 with an NTSC RF modulator, designed for use with North American TVs, instead of the UK PAL RF modulator which was used for units sold in Portugal.

List of ZX80 and ZX81 clones

clones of the ZX81
Unauthorized clones of the ZX81 were produced in several countries.
The following is a list of clones of Sinclair Research's ZX80 and ZX81 home computers:

Clive Sinclair

Sir Clive SinclairSinclairClive Marles Sinclair
The ZX81's commercial success made Sinclair Research one of Britain's leading computer manufacturers and earned a fortune and an eventual knighthood for the company's founder Sir Clive Sinclair.
Sinclair later moved into the production of home computers and produced the Sinclair ZX80, the UK's first mass-market home computer for less than £100, and later, with Sinclair Research, the ZX81 and ZX Spectrum; the latter is widely recognised for its importance in the early days of the British home computer industry.

Sinclair Research

SinclairScience of CambridgeSinclair Research Ltd
The ZX81 is a home computer that was produced by Sinclair Research and manufactured in Dundee, Scotland by Timex Corporation.
In March 1981, Sinclair Computers was renamed Sinclair Research Ltd and the Sinclair ZX81 was launched.

ZX81 character set

character set of the successor ZX81machine's character setnon-ASCII character set
It can display 24 lines of 32 characters each, and by using the selection of 2×2 block character graphics from the machine's character set offers an effective 64 × 44 pixel graphics mode, also directly addressable via BASIC using the PLOT and UNPLOT commands, leaving 2 lines free at the bottom.
The ZX81 character set is the character encoding used by the Sinclair Research ZX81 family of microcomputers including the Timex Sinclair 1000 and Timex Sinclair 1500.

Home computer

home computershomehome computing
The ZX81 is a home computer that was produced by Sinclair Research and manufactured in Dundee, Scotland by Timex Corporation.
In the early part of the 1980s, the dominant microprocessors used in home computers were the 8-bit MOS Technology 6502 (Apple, Commodore, Atari, BBC Micro) and Zilog Z80 (TRS-80, ZX81, ZX Spectrum, Commodore 128, Amstrad CPC).

1K ZX Chess

Nonetheless, ingenious programmers are able to achieve a surprising amount with just 1 KB. One example is 1K ZX Chess by David Horne, which includes most of the rules of chess in 672 bytes.
1K ZX Chess is a 1982 chess program for the unexpanded Sinclair ZX81.

ZX80

Sinclair ZX-80Sinclair ZX80Sinclair ZX80 RAM pack units
It was launched in the United Kingdom in March 1981 as the successor to Sinclair's ZX80 and was designed to be a low-cost introduction to home computing for the general public.
However this was mainly a cost-reduction effort; the hardware functionality and system programs were very similar, with the only significant difference being the NMI-generator necessary for slow mode in the ZX81 (see ZX81 for technical details), and the 4K integer-only Sinclair BASIC upgraded to 8K floating-point-capable, with the upgraded ROM also available as upgrade for the ZX80.

Semigraphics

block graphicstext semigraphicsa matrix of blocky pixels instead of a letter
It can display 24 lines of 32 characters each, and by using the selection of 2×2 block character graphics from the machine's character set offers an effective 64 × 44 pixel graphics mode, also directly addressable via BASIC using the PLOT and UNPLOT commands, leaving 2 lines free at the bottom.
But dividing an 8×8 character in 2×2 "pixels" was also common (it was, for example, used in the Sinclair ZX81).

Microprocessor

microprocessorsprocessorchip
There are only three other onboard chips: a 3.5 MHz Z80A 8-bit microprocessor from NEC, an uncommitted logic array (ULA) chip from Ferranti, and an 8 KB ROM providing a simple BASIC interpreter.
This delivered such inexpensive machines as the Sinclair ZX81, which sold for US$99.

Timex Group USA

TimexTimex CorporationWaterbury Clock Company
The ZX81 is a home computer that was produced by Sinclair Research and manufactured in Dundee, Scotland by Timex Corporation.
In a joint venture with Sinclair Research Ltd., the company entered the home computer business, selling such computers as the Timex Sinclair 1000 and succeeding machines, modeled on the ZX81 and ZX Spectrum.

BASIC

BASIC programming languagecompiled BASICBASIC IV
There are only three other onboard chips: a 3.5 MHz Z80A 8-bit microprocessor from NEC, an uncommitted logic array (ULA) chip from Ferranti, and an 8 KB ROM providing a simple BASIC interpreter.
Sinclair BASIC was introduced in 1980 with the Sinclair ZX-80, and was later extended for the Sinclair ZX-81 and the Sinclair ZX Spectrum.

Sinclair C5

C5
As he told the Sunday Times in April 1985, "We only got involved in computers in order to fund the rest of the business", specifically the development of the ultimately unsuccessful TV80 pocket television and C5 electric vehicle.
Sinclair intended it to prove the viability of electric personal transport; the hope was that, just as Sinclair had found with home computers like the hugely successful ZX81 and ZX Spectrum, an affordable electric vehicle could unleash pent-up demand for a market that did not previously exist.

Membrane keyboard

membraneflat-panel membranemembrane (flat foil) keyboard
The machine had no power switch or any moving parts, with the exception of a VHF TV channel selector switch present on early "ZX81 USA" models and the Timex-Sinclair 1000, and it used a pressure-sensitive membrane keyboard for manual input.
Sinclair ZX81 (similar to the preceding entry)

Sinclair BASIC

BASICSpectrum's BASIC
This enabled a fuller implementation of a version of ANSI Minimal BASIC (termed Sinclair BASIC by the company).
It evolved through the floating-point 8K BASIC for the ZX81 and TS1000 (which was also available as an upgrade for the ZX80 ), and became an almost complete version in the 16 KB ROM ZX Spectrum.

Gate array

ULAgate-arrayULAs
There are only three other onboard chips: a 3.5 MHz Z80A 8-bit microprocessor from NEC, an uncommitted logic array (ULA) chip from Ferranti, and an 8 KB ROM providing a simple BASIC interpreter.
Sinclair Research ported an enhanced ZX80 design to a ULA chip for the ZX81, and later used a ULA in the ZX Spectrum.

Ferranti

Ferranti Defence SystemsFerranti International plcFerranti Ltd
There are only three other onboard chips: a 3.5 MHz Z80A 8-bit microprocessor from NEC, an uncommitted logic array (ULA) chip from Ferranti, and an 8 KB ROM providing a simple BASIC interpreter.
In the early eighties, Ferranti produced some of the first large uncommitted logic arrays (ULAs), used in home computers such as the Sinclair ZX81, Sinclair ZX Spectrum, Acorn Electron and BBC Microcomputer.

Steve Vickers (computer scientist)

Steve VickersSteven Vickers
The code was written by John Grant, the owner of Nine Tiles, and Steve Vickers, who had joined the company in January 1980.
In the early 1980s, he wrote ROM firmware and manuals for three home computers, the Sinclair ZX81 and ZX Spectrum and the Jupiter Ace.

ZX Spectrum

SpectrumSinclair ZX SpectrumSinclair Spectrum
When sales fell in the wake of the launch of its successor, the ZX Spectrum, Sinclair reduced the price of the pre-assembled version to £49.95 in May 1982.
Referred to during development as the ZX81 Colour and ZX82, it was launched as the ZX Spectrum by Sinclair to highlight the machine's colour display, compared with the black and white of its predecessor, the ZX81.

ZX Printer

Unfortunately for Vickers, he introduced a briefly notorious error – the so-called "square-root bug" that caused the square root of 0.25 to be returned erroneously as 1.3591409 – as a result of problems with integrating the ZX Printer code into the ROM.
The Sinclair ZX Printer is a spark printer which was produced by Sinclair Research for its ZX81 home computer.

ZX80 character set

character setcharacter set of the predecessor ZX80
The ZX81 conserves its memory to a certain extent by representing entire BASIC commands as one-byte tokens, stored as individual "characters" in the upper reaches of the machine's unique (non-ASCII) character set.
The 8K BASIC ROM of the follow-up ZX81 model was also available as an upgrade for the ZX80, replacing its integer-only 4K BASIC ROM.

Psion (company)

PsionPsion PLCPsion Software Ltd
Existing companies also sold software; Psion produced a series of ZX81 programs in close association with Sinclair, including a flight simulator, while ICL's range of ZX81 programs sold over 100,000 cassettes in less than three months.
The company developed games and other software for the ZX81 and ZX Spectrum home computers, released under the Sinclair/Psion brand.

3D Monster Maze

Some ZX81 games achieved lasting fame, such as 3D Monster Maze, a tense first-person perspective game that involved the player escaping a labyrinth with a Tyrannosaurus rex in pursuit.
3D Monster Maze is a computer game developed from an idea by J.K.Greye and programmed by Malcolm Evans in 1981 for the Sinclair ZX81 platform with the 16 KB memory expansion.

Texas Instruments TI-99/4A

TI-99/4ATI-99/499/4A
The TS1000/ZX81's price advantage was erased when its main rivals – the Texas Instruments TI99/4A and the Commodore VIC 20 – had their prices cut to below the all-important $100 mark.
TI-99/2, a 4K RAM, 32K ROM computer with no color, sound, or joystick port and a Mylar keyboard. TI designed the computer in four and one half months to sell for under $100 and compete with the Sinclair ZX81 and Timex Sinclair 1000. Based on the TMS9995 CPU running at 10.7 MHz and with a built-in RF modulator, performance greatly increased when the screen was blank. The University of Southwestern Louisiana developed system software. 99/2 software ran on the 99/4A, but not vice versa. Working prototypes appeared at the January 1983 Consumer Electronic Show (CES). Home-computer prices declined so quickly, however, that by mid-1983 the 99/4A sold for $99. The company canceled the 99/2 in April 1983, but planned to exhibit it at the June CES until other companies' press conferences there indicated that competition would increase.