Sinclair ZX81
Encyclopedia
The ZX81 was a home computer
produced by Sinclair Research and manufactured in Scotland
by Timex Corporation
. 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. It was hugely successful and more than 1.5 million units were sold before it was eventually discontinued. The ZX81 found commercial success in many other countries, notably the United States, where Timex manufactured and distributed it under licence. Timex later produced its own versions of the ZX81 for the US market – the Timex Sinclair 1000
and Timex Sinclair 1500. Unauthorised clones of the ZX81 were produced in a number of countries.
The ZX81 was designed to be small, simple, and above all cheap, using as few components as possible to keep the cost down. Video output was to a television set rather than a dedicated monitor. Programs and data were loaded and saved onto audio tape cassettes. It had only four silicon chips on board and a mere 1 kB of memory. The machine had no moving parts – not even a power switch – and used a touch-sensitive membrane keyboard
for manual input. The ZX81's limitations prompted the emergence of a flourishing market in third-party peripherals to improve its capabilities. Such limitations, however, achieved Sinclair's objective of keeping the cost of the machine as low as possible. Its distinctive design won awards in the UK and abroad.
The ZX81 could be bought by mail order in kit form or pre-assembled. In what was then a major innovation, it was the first cheap mass-market home computer that could be bought from high street
stores, led by W.H. Smith and soon many other retailers. The ZX81 marked the first time that computing in Britain became an activity for the general public, rather than the preserve of businesspeople and electronics hobbyists. It inspired the creation of a huge community of enthusiasts, some of whom founded their own businesses producing software and hardware for the ZX81. Many went on to play a major role in the British computer industry in later years. 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
.
of on-board memory that could be expanded externally to 16 kB. Its single circuit board is housed inside a wedge-shaped plastic case measuring 167 millimetres (6.6 in) deep by 40 millimetres (1.6 in) high. The memory is provided by either a single 4118 (1024 Bit × 8) or two 2114 (1024 Bit × 4) RAM chips. There are only three other chips on board: a 3.5 MHz Z80A 8-bit
microprocessor
from Nippon Electric (now NEC
), an uncommitted logic array
(ULA) chip from Ferranti
and a 8 kB ROM providing a simple BASIC
interpreter. The entire machine weighs just 350 grams (12.3 oz). The memory can be expanded externally to a maximum of 16 kB. Early versions of the external cartridge contained 15 kB of memory using an assortment of memory chips, while later versions contained 16 kB of chips but the lowest addressed kilobyte was disabled.
The front part of the case is occupied by an integrated 40-key membrane keyboard displaying 20 graphic and 54 inverse video characters. Each key has up to five functions, accessed via the SHIFT and FUNCTION keys or depending on context. For example, the P key combined the letter 'P', the " character and the BASIC commands PRINT and TAB. The ZX81 uses a standard QWERTY
keyboard layout
, with some extra keys that are unfamiliar to modern eyes, such as a RUBOUT key (instead of DELETE) and a NEW LINE key rather than RETURN or ENTER. The keyboard is mechanically very simple, consisting of 40 pressure-pad switches and eight diodes under a plastic overlay, connected in a matrix of eight rows and five columns.
The ZX81's primary input/output is delivered via four sockets on the left side of the case. The machine uses an ordinary UHF television set to deliver a monochrome picture via a built-in RF modulator. It can display 24 lines of 32 characters each, and by utilising the selection of 2x2 block character graphics
from the machine's character set offered an effective 64 × 44 pixel graphics mode, also directly addressible via BASIC using the PLOT and UNPLOT commands. Two 3.5 mm jacks connect the ZX81 to the EAR (output) and MIC (input) sockets of an audio cassette recorder, enabling data to be saved or loaded at a rate of 250 baud
. This provides a somewhat temperamental storage medium for the machine, which has no built-in storage capabilities. The ZX81 requires 420 mA of power at 7–11 V
DC
, delivered via a custom 9 V Sinclair DC power supply.
The ULA chip, described by the ZX81 manual as the "dogsbody" of the system, has a number of key functions that competing computers shared between multiple chips and integrated circuits. These comprise:
The ZX81's built-in RF modulator
can output a video picture to either a UHF 625 line colour or monochrome television (used in the UK, Australia, and most western European countries). France required a slightly modiified version of the machine to match the positive video modulation of their sets. The USA and Canada required a different ULA chip and modulator to cope with their 525 line VHF television systems. Both the ZX81 and its predecessor, the ZX80, have a significant drawback in the way that they handle visual output. Neither machine has enough processing power to run at full speed and simultaneously maintain the screen display. On the ZX80, this means that the screen goes blank every time the machine carries out a computation and causes an irritating flicker whenever a shorter computation – such as processing a keystroke – takes place.
The ZX81's designers adopted an improved approach, involving the use of two modes called SLOW and FAST respectively. In SLOW mode, also called "compute and display" mode, the ZX81 concentrates on driving the display. It runs the current program for only about a quarter of the time – in effect slowing the machine down fourfold, although in practice the speed difference between FAST and SLOW modes depends on what computation is being done. In FAST mode processing occurs continuously but the display is abandoned to its own devices – equivalent to the ZX80's standard operating mode.
Another hardware quirk produced one of the most distinctive aspects of the ZX81's screen display – during loading or saving, moving zigzag stripes appear across the screen. The same pin on the ULA is used to handle the video signal as well as the tape output, producing the stripes as an interference pattern of sorts. As well as this, the ULA cannot maintain the display during SAVE and LOAD operations, as it has to operate continuously to maintain the correct baud rate for data transfers.
The unexpanded ZX81's tiny memory presented a major challenge to programmers. Simply displaying a full screen takes up 768 bytes, the system variables take up another 125 bytes and the program, input buffer and stacks need more memory on top of that. Nonetheless, ingenious programmers were able to achieve a surprising amount with just 1 kB. One notable example was 1K ZX Chess
by David Home, which is somewhat misnamed as it managed to squeeze most of the rules of chess into just 672 bytes. The ZX81 conserved 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 edge connector or external interface at the rear of the ZX81 is an extension of the main printed circuit board. This provides a set of address, control, and data lines that can be used to communicate with external devices. Enthusiasts made use of this facility to create a wide range of add-ons for the ZX81.
as an example of a modern device that costs about the same in real terms as a ZX81 did in 1981 but is far smaller.
Clive Sinclair's first company Sinclair Radionics, established in 1962, made its name producing a wide range of cheap electronics aimed at the hobbyist market. Its products included amplifier
s, radios, multimeter
s and other items generally sold in kit form to hi-fi enthusiasts and other electronics hobbyists. The company entered a new market in 1972 when it launched the first "slimline" pocket calculator, the Sinclair Executive
. It was a major success that Radionics followed up by launching a wide range of pocket calculators. The company's subsequent expansion made it Europe's biggest calculator manufacturer by 1975.
By the late 1970s, however, Sinclair Radionics was in serious difficulties. It lost its ability to compete effectively in the calculator market following the launch of a new generation of Japanese-produced calculators with liquid crystal display
s, which were much more capable and power-efficient than Sinclair's LED
calculators. Projects to develop a pocket television and digital watch turned out to be expensive flops. The company made losses of over £350,000 in 1975–76, bringing it to the edge of bankruptcy. In July 1977 Radionics was rescued by a state agency, the National Enterprise Board
(NEB), which recapitalised it, provided a loan facility and took effective control of the company by acquiring a 73% stake.
Clive Sinclair's relationship with the NEB was fraught due to conflicting notions about which direction the company should go. Radionics had begun a project to develop a home computer but the NEB wanted to concentrate on the instrument side of the business, which was virtually the only area where Radionics was profitable. Sinclair disagreed vehemently with what he characterised as the view "that there was no future in consumer electronics". This and other disputes led to Sinclair resigning from Radionics in July 1979.
While he was struggling with the NEB, Clive Sinclair turned to a "corporate lifeboat" in the shape of an existing corporate shell under his exclusive control – a company called Ablesdeal Ltd, which he had established in 1973 and later renamed Science of Cambridge. It became a vehicle through which he could pursue his own projects, free of the interference of the NEB. Despite his later success in the field, Sinclair saw computers as merely a means to an end. 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. In an interview with Practical Computing, Sinclair explained:
Sinclair's first home computer was the MK14
, which was launched in kit form in June 1978. It was a long way from being a mass-market product. Its very name – MK standing for "Microcomputer Kit" – was indicative of its origins as a product developed by, and for, hobbyists. It had no screen but instead used an LED segment display (though Science of Cambridge did produce an add-on module allowing it to be hooked up to a UHF TV); it had no case, consisting of an exposed circuit board; it had no built-in storage capabilities and only 256 byte
s of memory; and input was via a 20-key hexadecimal
keyboard. Despite the limitations of the machine it sold a respectable 10–15,000 units; by comparison, the much more expensive Apple II
had only sold 9,000 units in the United States, a much bigger market, in 1978. This success convinced Clive Sinclair that there was an untapped market for low-cost computers that could profitably be exploited.
Sinclair followed up the MK14 by producing the ZX80, at the time the world's smallest and cheapest computer, which was launched in January 1980 costing £99.95 (equivalent to £319 at 2009 prices.) The company conducted no market research whatsoever prior to the launch of the ZX80; according to Clive Sinclair, he "simply had a hunch" that the general public was sufficiently interested to make such a project feasible and went ahead with ordering 100,000 sets of parts so that he could launch at high volume.
The ZX80's design introduced many key features that were carried over to the ZX81; as Sinclair himself later said, "the ZX80 was very much a stepping stone to the ZX81". The design was driven entirely by the desired price point – the machine had to cost less than £100 but still make a healthy profit. Its distinctive wedge-shaped white case concealing the circuitry and the touch-sensitive membrane keyboard were the brainchild of Rick Dickinson
, a young British industrial design
er who had recently been hired by Sinclair. As he later recalled of Sinclair's approach, "Everything was cost driven. The design was the face of the machine." The unconventional keyboard was the outcome of Sinclair's cost-cutting. It made use of a sheet of plastic, on which the keys were printed, overlaying a metallic circuit that registered when a key was pressed. This avoided the expense of providing a typewriter-style keyboard, though the design had many drawbacks when it came to usability and "feel".
Inside the case, there were many more similarities with the ZX81. Like its successor, it used the Z80A microprocessor and had only 1 kB of on-board RAM. It came with a specially written BASIC interpreter on a dedicated ROM chip and could use a television as a display. It relied on an ordinary cassette tape recorder for data storage. The main difference between the two machines lay in the internal software; when the ZX81 was released, ZX80 owners were able to upgrade by the relatively simple expedient of soldering a new ROM onto the circuit board.
The ZX80 was an immediate success, selling 20,000 units over the following nine months. Science of Cambridge was producing ZX80s at the rate of 9,000 a month by the end of 1980 and within 18 months of its launch the company had sold 100,000 units. The commercial success of the ZX80 made a follow-up product inevitable. The company was renamed Sinclair Computers in November 1980, reflecting its new focus, and became Sinclair Research in March 1981.
, to be broadcast in 1982, aimed at popularising computing and programming. The BBC intended to commission an existing manufacturer to provide it with a BBC-branded home computer to tie in with the series. When Sinclair got wind of the project in December 1980, he wrote to the BBC informing them that he would be announcing a new version of the ZX80, to be called the ZX81, in the spring of 1981. It would remedy some of the ZX80's deficiencies and would be both cheaper and more advanced. Sinclair naturally wanted the ZX81 to be a candidate for the BBC contract and lobbied for its adoption. He pointed out that there were already 40,000 users of the ZX80 and that by the time the series was broadcast there were likely to be upwards of 100,000 ZX81 users (which turned out to be an underestimate by over 400,000 – an indication of how the ZX81's success exceeded even Sinclair's expectations).
A prototype ZX81 was demonstrated to BBC representatives in January 1981, while Sinclair's local rival Acorn Computers
put forward their proposed Proton computer, a design – of which a prototype did not yet exist – based on the Acorn Atom
. To Sinclair's dismay, the contract to produce the BBC Microcomputer went to Acorn, which launched the machine in January 1982. Paul Kriwaczek, the producer of The Computer Programme, explained his reservations in a March 1982 interview with Your Computer
:
Sinclair was bitterly critical of the BBC's decision, accusing it of incompetence and arrogance. Shortly after Acorn won the BBC contract the Government issued a recommended list of computers that schools could purchase, with the aid of a grant, for half price. Sinclair's computers were not included on the list. Sinclair responded by launching his own half-price deal, offering schools the chance to buy a ZX81 and 16 kB RAM pack for £60, plus a ZX Printer at half price, for a total cost of £90. As the cheapest Government-approved system was £130, this was an attractive offer for many schools and about 2,300 bought Sinclair's package.
The development of the ZX81 got underway even before the ZX80 had been launched. Sinclair's chief engineer, Jim Westwood
, was given the task of improving the ZX80's hardware to reduce the number of components and thus bring down the cost. He also sought to fix some of the more annoying problems with the ZX80. Westwood and his colleagues found that the component count could be reduced greatly by combining eighteen of the ZX80's chips into a single uncommitted logic array (ULA), a type of general-purpose chip that allowed manufacturers to reprogram it to meet their particular requirements rather than having to develop their own customised chip at greater expense. Ferranti
produced the new chip for Sinclair, who hailed Westwood's design as a triumph of innovation: "The ZX81 had four chips when our nearest competitor in this respect, the TRS-80, had 44." Only 70% of the logic gates on the ULA were supposed to be used, but Sinclair decided to obtain maximum benefit by using them all. This resulted in the machine becoming uncomfortably warm during usage. Computing folklore held that the ZX81 had to be refrigerated by balancing a carton of cold milk on top of the case.
The ZX81's ROM was doubled to 8 kB, from the ZX80's 4 kB ROM. This enabled a fuller implementation of a version of ANSI Minimal BASIC (termed Sinclair BASIC
by the company). Clive Sinclair re-commissioned a company called Nine Tiles, which had produced the ZX80 ROM, to develop the new ROM software for the ZX81. The code was written by John Grant, the owner of Nine Tiles, and Steve Vickers, who had joined the company in January 1980. Grant concentrated on the software that drove the ZX81's hardware, while Vickers developed the new BASIC and the accompanying manual. Sinclair's brief to the pair was fairly non-specific but primarily concerned remedying a key defect of the ZX80 so that the new machine could be used for practical programming and calculations. Vickers later recalled:
The new ROM incorporated trigonometric
and floating point
functions, which its predecessor had lacked – the ZX80 could only deal with whole numbers. Grant came up with one of the ZX81's more novel features, a syntax checker that indicated errors in BASIC code as soon as it was entered (rather than, as was standard at the time, only disclosing coding errors when a program was run). 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. Although it was eventually fixed, the bug became the subject of controversy and Sinclair was forced to replace some of the ZX81s sold to early customers. On a more positive note, Vickers' work on the manual was received favourably, being described in 1983 as "one of the classic texts on BASIC". Max Phillips commented in a What Micro? retrospective:
The task of designing the ZX81's case again fell to Rick Dickinson, who produced an updated version of the ZX80's wedge-shaped case. This time round, the design team were able to use injection moulding
, which enabled them to deliver a higher-quality case. Dickinson originally envisaged the ZX81 as "an expandable range of boxes following a vaguely modular approach with a common width", though this approach was eventually dropped. From start to finish, the design process took about six months.
The ZX81 was launched on 5 March 1981 in two versions (though with identical components) – a pre-assembled machine or a cheaper kit version, which the user could assemble himself. Both versions were manufactured in Dundee
, Scotland
by Timex Corporation
at the company's Dryburgh
factory. Timex had not been an obvious choice of manufacturing subcontractor, as the company had little previous experience in assembling electronics. It was a well-established manufacturer of mechanical watches but was facing a crisis at the beginning of the 1980s. Profits had dwindled to virtually zero as the market for mechanical watches stagnated in the face of competition from the digital and quartz watches. Recognising the trend, Timex's director, Fred Olsen
, determined that the company would diversify into other areas of business.
This shift by Timex came at an ideal time for Sinclair. The ZX80 had proved more popular than expected and Sinclair's existing manufacturer, a small electronics company in St Ives
, lacked the resources to deal with the demand. Timex took over production of the ZX80 late in 1980. The arrangement worked well for both companies and Timex took on the manufacture of the ZX81, aided by capital investment in its Dundee plant. Sinclair initially planned to produce 10,000 ZX81s a month, rising to 30,000 a month within a year. However, Timex initially had significant problems in producing enough ZX81s to satisfy demand. As a consequence, it took up to nine weeks for ZX81s to be delivered by mail order. It was not until September 1981, five months after the launch of the ZX81, that the delivery times finally came down to the promised twenty-eight days. Those who already owned or had recently ordered the ZX80 were not left out in the cold. Anyone who had ordered a ZX80 in the two weeks before the ZX81's launch would receive the newer machine, while existing owners were able to upgrade their ZX80s by soldering an extra £20 ROM chip into the circuit board.
The reliability of the ZX81 was a somewhat controversial issue. W.H. Smith, one of the machine's key distributors, had a company policy of ordering a third more ZX81s than were actually required for sale, so that it would have enough replacements for faulty machines. Similar problems were reported in the US market, where contemporary reports suggested that only a third of the ZX81s shipped actually worked. However, figures released by Sinclair claimed that only 2.4 per cent of pre-assembled machines were returned, although 13 per cent of kits were returned. Clive Sinclair strongly denied any problem with reliability:
The higher failure rate of the kits was put down to customers breaking the components by inserting or soldering them the wrong way, though Sinclair admitted that there was a persistent problem with power supplies that affected both kits and pre-assembled ZX81s. The bigger problem was perhaps Sinclair's after-sales service, or rather the lack thereof, which Robin Clarke of New Scientist
described as "one of the worst after-sales performance records of any company ever established." The Financial Times observed that "Clive Sinclair's offices are filled with returned computers which can take months to be repaired." The company's slowness in replacing returns and delivering freshly ordered machines meant that Sinclair Research gained an unenviable reputation for poor customer service.
), which had provided marketing services for Sinclair since 1971 and was to continue doing so until 1985. Sinclair's entry into the nascent home computing market gave Primary Contact a major challenge – how to market a product simultaneously at hobbyists and at the "man on the street", who probably had little or no computer literacy. The answer was to pursue what the journalist David O'Reilly of MicroScope
magazine described as a single-minded "user-friendly strategy." Chris Fawkes, one of Primary Contact's directors, explained: "We brought personal computers to the mass market by showing that you didn't have to be a whizzkid to use one." As Clive Sinclair put it in a 1982 interview with Your Computer,
According to the US market analyst Ben Rosen, by pricing the ZX81 so low, "Sinclair has opened up a completely new market among people who had never previously considered owning a computer." Clive Sinclair acknowledged the role that guesswork had played in his decision to launch the ZX81 on such a large scale: "It was a surmise that the man in the street would want such a computer. He does, and our information is that a lot of people are using the machines avidly." A New Scientist retrospective published in 1986 commented:
High-profile advertising was central to the marketing campaign. Although Sinclair Research was a relatively small company, it had a long-standing policy of using large-scale advertisements that stood out in stark contrast to the more muted advertisements of other manufacturers. Superlatives, exhortations, appeals to patriotism, testimonials, eye-catching drawings and photographs on double-page spreads, varying from month to month, were used to drum up mail order business for Sinclair. The launch advertising for the ZX81 illustrates this approach. A photograph of the ZX81 alongside the official Sinclair peripherals dominated the centre of a double-page spread. The value for money of Sinclair's products was emphasized by the prices being printed in larger type than any other text on the spread. The ZX81's benefits were promoted with the aspirational slogan "Sinclair ZX81 Personal Computer – the heart of a system that grows with you". The advertisement highlighted ZX81 BASIC Programming, the manual written by Steve Vickers, as "a complete course in BASIC programming, from first principles to complex programs." The educational benefits of the ZX81 were stressed ("it's still very simple to teach yourself computing") and its technical advantages were explained in relatively non-technical terms. For instance, the ZX81's idiosyncratic method of typing commands with a single keystroke – the result of the memory-saving method of using one-byte tokens to represent keywords – was presented as "eliminat[ing] a great deal of tiresome typing". The ZX81's British character was emphasized; it was "designed by Sinclair and custom-built in Britain." Sinclair's advertising in the United States provides an illustration of how the company perceived the ZX81's purpose:
This approach to advertising was driven by Sinclair's reliance on mail-order marketing. It came with a high up-front cost in terms of purchasing space in publications but it had the advantage of ensuring that all sales were firm and pre-paid. A big splash on launch produced a large influx of cash at the outset of a campaign, though it did also depend on the advertiser having enough product to satisfy the initial surge in demand. The advertisements served an additional purpose of priming the market for over-the-counter sales by "getting the story across", as Clive Sinclair put it: "Not that big a proportion do buy on mail order, but they see the ads, and that helps to prepare them for buying when the item appears in the shops."
Sinclair himself became a focal point for the marketing campaign, putting a human face on the business, while Sinclair Research was portrayed in the media as a plucky British challenger taking on the technical and marketing might of giant American and Japanese corporations. As David O'Reilly noted, "by astute use of public relations, particularly playing up his image of a Briton taking on the world, Sinclair has become the best-known name in micros." The popular press soon latched onto the image. His "Uncle Clive" persona is said to have been created by the gossip columnist for Personal Computer World
, while the media praised Sinclair as a visionary genius (or even, in the words of The Sun, "the most prodigious inventor since Leonardo
.") As Ian Adamson and Richard Kennedy put it, Sinclair outgrew "the role of microcomputer manufacturer and accepted the mantle of pioneering boffin
leading Britain into a technological utopia."
Pricing was central to the marketing strategy, as it had been through Sinclair's career. The ZX81 had been designed to meet a £70 price point and was launched at a price of £69.95 (built) or £49.95 (kit). One Sinclair brochure presented a side-by-side comparison of the ZX81 with the four machines that Sinclair considered its main rivals – the Acorn Atom
, Apple II Plus
, Commodore PET
and TRS-80
. The comparison highlighted the vast differences in cost, from £630 in the case of the Apple II Plus to just £70 for the ZX81, though even by Sinclair's own comparison the Apple was by far the more capable machine.
According to Sinclair himself, the £69.95 price was chosen after applying the "experience curve" developed by the Boston Consulting Group
. Sinclair's prior experience in the calculator market had highlighted the fact that a product will be more profitable selling at (for instance) twice the manufactured cost than at three times. He could have launched the ZX81 at a higher price, marketing it in a more traditional way as a premium product, but chose not to. In effect, he used the lower price to establish an unassailable lead before the competition moved in.
An essential part of Sinclair's marketing strategy was to use regular cost-cutting at strategic intervals to maintain market share. Ian Adamson and Richard Kennedy comment that Sinclair's approach was "to secure and extend [his] market lead and panic the competition. While most companies reduce prices when their products are in steep decline, Sinclair tends to discount shortly after sales have peaked. The advantage of his approach is that vacillating customers are drawn into the fold while the product's promotion retains a commercial urgency, and the costings of the competition are thrown into utter disarray."
This tactic proved highly successful. When sales of the ZX81 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. It was cut by another £10 the following April. Despite the increased competition from much more capable computers, the ZX81 was still shipping in excess of 30,000 units a month even as late as July 1983, more than two years after it had been launched. By that time, over 1.5 million ZX81s had been sold.
Smith's had begun selling audio and photographic equipment and calculators at the end of the 1970s, with a modest degree of success. In 1980 its marketing development manager, John Rowland, hit upon the idea of creating "Computer Know-How" sections in major branches to sell computer books and magazines. Most of the items on display were imports from the United States but their relatively high cost reduced their attractiveness to the casual buyer. The commercial success and mass market potential of the ZX80 caught Rowland's interest; he approached Sinclair, saw a prototype ZX81 and agreed to market the machine through Smith's on an exclusive basis for the first six months after launch. As Rowland put it, "what we've done now is bring the computer-orientated publications together with an actual computer, to create the Computer Know-How section of the store", alongside computer software and blank cassette tapes. The ZX81 would be sold in 112 stores around the UK and would serve as the centrepiece of the "Computer Know-How" sections.
Selling the ZX81 over the counter was seen as something of a gamble and Rowland's colleagues were initially unenthusiastic about the scheme. Branch buyers thought that the ZX81 was unlikely to sell more than 10–15 units per branch at launch. Rowland himself thought that the ZX81 would sell about 10,000 units during the first five months of the retail agreement, equivalent to one month's mail order sales by Sinclair. In the event, the ZX81 was a massive success for Smith's. The "Computer Know-How" sections were swamped with eager customers, overwhelming the 300 staff who had been trained to demonstrate the machines; a Financial Times correspondent wrote of being "dazed and bewildered by the crowds of schoolchildren clustered round the ZX81 in your local branch of W.H. Smith." Within a year, Smith's had sold 350,000 ZX81s, making an estimated net profit of £10 million. Sales of peripherals, software, books and magazines netted even more profit.
Other distributors soon joined the act. The British chain stores Boots, John Menzies
and Currys
began selling the ZX81 as soon as Smith's exclusive distribution deal expired and a number of companies secured overseas distribution rights for the ZX81, which was being sold in 18 countries by March 1982. Sinclair launched the ZX81 in the United States in November 1981 at a price of $149.95 assembled and $99.95 in kit form, initially selling directly to the American market by mail order. Sales reached 15,000 a month by January 1982, while American Express
sold thousands more to its own customers. In February 1982 Timex obtained a licence from Sinclair to sell the ZX81 directly through thousands of retail outlets in the US, paying Sinclair Research a 5 per cent royalty on all Sinclair hardware and software sold by Timex. The company was later to produce its own licensed clones and variants of the ZX81. In December 1981 Mitsui
obtained rights to distribute the ZX81 in Japan, selling it by mail order for ¥
38,700 (equivalent to £83 in 1982 prices), and had sold 5,000 units by July 1982. The Japanese market's favourable reaction to the ZX81 led Mitsui to begin selling the ZX81 over the counter in large bookshops from September 1982, with annual sales of 20,000 units predicted.
The ZX81 was also sold for a while in duty-free shop
s at UK airports. However, this fell foul of government export restrictions aimed at preventing the Soviet bloc countries from obtaining Western high technology goods. It was not uncommon for visitors from the Soviet Union
and other eastern European countries to pick up gadgets in Western countries with the aim of transferring their technology
to their own states' industries. In 1983 the government ordered that the ZX81s were to be withdrawn from sale at airports. There was no such restriction on sales to communist China
and in November 1983 Sinclair Research announced that it had signed an agreement to export ZX81 kits to a factory in Guangzhou
, where they would be assembled for the Chinese market.
In the Netherlands, the regular Sinclair ZX81 was for sale as well as a Bang & Olufsen
branded version called Beocomp.
put it in Your Computer, "the ZX81 is both a delight and a disappointment". He applauded the improvements that had been made over the ZX80, such as a much better manual, display and string
handling, and called the ZX81 "a very good first computer" that "will open the world of computing to many who would be denied access to it by cost." However, the built-in memory was so small that use of a memory expansion pack was "mandatory for any worthwhile use". He also found the ZX81 to be alarmingly unreliable, having to have his first two test machines replaced before getting one that worked properly.
New Scientist's Malcolm Peltu commented that it was "great technical value for money particularly for computing enthusiasts" but thought that others were "likely to be bored very quickly by the basic system". He highlighted weaknesses in the manual and Sinclair's accompanying software, criticising them for "a misconceived design and sloppiness in execution which make the machine seem harder to use and more limited than it should" and questioned whether it might be more worthwhile to save up for a more powerful computer such as Acorn or Commodore's offerings. Overall, he concluded, the ZX81 might have a limited value in helping to teach BASIC programming and overcoming psychological barriers to computing, but "the Sinclair systems have a long way to go before they raise the quality and level of understanding of the nature and use of computer-based information systems among compute unbelievers."
While Personal Computer World editor Derek Cohen was on holiday in May 1981, his colleagues publicised the magazine's review of the ZX81 with a cover showing a chimpanzee with the machine above the strapline "Editor benchtests the ZX81". (The chimp returned in later issues to "benchtest" all of Sinclair's subsequent computers.) The review, which was actually written by PCW staffer Dave Tebbutt, acknowledged that the machine had significant shortcomings but nonetheless represented "absolutely amazing value for money". He described the ZX81 as "a lovely product which will have enormous appeal to people wanting to find out more about computers, but without it costing them an arm and a leg" and concluded: "If you know nothing about computers and you want to enjoy finding out about them, then this machine offers a value for money way of doing just that. Children will love the ZX81, there can be no question about that, and I suspect that more than a few people who are already familiar with computers will buy one, just to have a bit of fun."
Paul Taylor of the Financial Times
found the ZX81 to be "a powerful and flexible little computer ideally suited as a fun introduction to the mysteries of home computing" but cautioned readers about its limitations. It lacked ready-made software, the keyboard was not easy to use, it did not have sufficiently advanced graphics to be able to replicate arcade-style games and its built-in memory was inadequate. Even so, he suggested, "the ZX81 is a unique British product, part toy, part puzzle, part learning tool and I think that, provided one accepts its limitations and recognises that any computer will only do what it is told to do, it is good value as an introduction to the hobby of home computing."
David Babsky described the ZX81 as "a wonderfully brainy little micro which won't let you waste your time and make a fool of yourself". In a comparison between the ZX81 and IBM PC published in Which Micro?, he commended the ZX81's user-friendliness and its on-the-fly syntax checking of BASIC programs, which he described as "the feature that I, as a newcomer to computing, want to see incorporated into every micro."
Sinclair released only two official peripherals for the ZX81 – a 16 kB RAM pack (actually the same one previously released for the ZX80, but rebadged) and the ZX Printer
, both of which plugged into the edge connector at the rear of the ZX81. They retailed at a launch price of £49.95 each but both had notable flaws. The RAM pack was top-heavy and was supported only by the edge connector. It had a habit falling out of its socket at crucial points and crashing the ZX81, losing anything that the user had typed in. Users turned to using sticky lumps of chewing gum, double-sided tape or Blu-Tack
to cure what became known as the "RAM pack wobble" problem. The ZX Printer was a tiny spark printer
that used two electrically charged styli to burn away the surface of aluminium-coated paper to reveal the black underlay. It worked reasonably well at first but its output deteriorated rapidly after a time.
Many peripherals aimed to remedy the ZX81's flaws and provide many new capabilities that Sinclair had not tackled. These included proper typewriter-style keyboards, wobble-free RAM packs providing up to 64 kB of extra memory, more advanced printers and sound generators – and even a hard disk interface, which Clive Sinclair thought was "quite overgilding the lily". A wide range of software was also published. Within only a year of the ZX81's launch, around 200 independent companies had been established to manufacture and sell Sinclair-compatible hardware. The people behind the ZX81 cottage industry were very often not computer professionals but were, as the Financial Times noted, "school teachers, civil servants, electrical engineers and technicians [who] have set up small operations in their own time."
A dramatic illustration of the ZX81's explosive popularity came in January 1982, when civil servant Mike Johnstone organised a "ZX Microfair" at Westminster Central Hall
. Seventy exhibitors set up their stalls with only a few hundred visitors expected in a hall with a capacity of 650 people. In the event, more than 12,000 people turned up and the police had to be called to control the crowd. Thousands of people, many of whom had travelled long distances to get there, queued outside for up to three hours to get into the hall. The exhibitors found themselves selling thousands of pounds' worth of software and hardware, "as fast as three pairs of hands on each stall could hand them over and stuff the fivers into improvised overflowing cash boxes."
Thousands of ZX81 programs were published, either as printed listings that could be typed in or as ready-made applications that could be loaded from cassette tape. Many computer magazines featured ZX81 program listings – some, such as Sinclair Programs, were dedicated entirely to listings – while many individuals became the archetypal "bedroom programmers", producing games and applications which they produced, marketed, recorded and sold from their own homes. Some went on to found their own software houses, employing teams of programmers – some of whom were still at school – to produce programs for the ZX81 and other computers. Existing companies jumped on the bandwagon as well, to profitable effect; 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. Psion's success with the ZX81 had a profound effect on the future of the company. Its work on the ZX81 database program Vu-File led to Psion switching its focus to the development of personal digital assistant
s, which resulted in the launch in 1984 of the Psion Organiser
, the world's first handheld personal computer. Some of the most popular ZX81 games (Psion's Flight Simulation being an example) were rewritten for the Spectrum to take advantage of the newer machine's colour and sound capabilities.
Enterprising programmers were able to produce games for the ZX81 using nothing more than text characters and the machine's limited number of inverse video graphical blocks. 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. Written in a combination of BASIC and machine code
, its innovative design led it to be hailed as the first home computer 3D game and a landmark in the history of computer and video games
.
One of the more bizarre software products for the ZX81 came about as a result of music companies attempting to capitalise on the popularity of Sinclair's computers. In 1983, EMI
released a single by Chris Sievey that had a ZX81 program recorded on the B-side. Island Records
responded with XL1
by Buzzcocks
frontman Pete Shelley
, packaged with a program for the ZX Spectrum.
Sinclair's licensing agreement with Timex enabled the American company to produce three clones or offshoots of Sinclair machines for the US market. These were the Timex Sinclair 1000
, Timex Sinclair 1500 (both variants of the ZX81) and the Timex Sinclair 2068
(a variant of the ZX Spectrum). The TS1000 was launched in July 1982 and sparked a massive surge of interest; at one point, the Timex phoneline was receiving over 5,000 calls an hour, 50,000 a week, enquiring about the machine or about microcomputers in general. It was virtually identical to the ZX81 save for rebranding and the addition of an extra 1 kB of memory, making for a grand total of 2 kB. In the five months following the TS1000's launch, the company sold 550,000 machines, earning Sinclair over $1.2 million in royalties.
Timex produced a second version of the ZX81 in the form of the TS1500, essentially an Americanised ZX81 launched in August 1983. It dispensed with the membrane keyboard and used a case similar to that of the ZX Spectrum, incorporating 16 kB of on-board memory. It was effectively a stopgap between the ZX81 and Spectrum. However, it was unsuccessful due to increased competition from rival US machines and the after-effects of Timex's botched marketing of the TS1000. Although the TS1000 had initially been a great success, Timex failed to provide the essential RAM pack upgrades to the market for two or three months after it launched the TS1000. Consumers would take the machine home, plug it in and find that it would not do anything useful due to the lack of memory.
In addition, consumers' attitude in the US was quite different to that in the UK. Clive Sinclair told Informatics magazine in June 1981 that "our competitors thought that consumers didn't want to learn programming. We [Sinclair Research] think they failed because of this and because of price." Timex evidently shared this belief but events proved it to be a false assumption. 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. Competitors such as Apple, Atari, Commodore and Texas Instruments promoted their machines as being for business or entertainment rather than education, highlighting the value of computers with ready-made applications and more advanced features such as graphics, colour and sound.
Consumers deserted the TS1000 once its novelty value had worn off and, as publishers of programming guides found to their cost, the American public showed little interest in using the machine to learn about computer programming. American retailers were left with large stocks of unsold machines. Burned by this experience, many were unwilling to stock the later Timex Sinclair machines in large numbers and the big chain stores dropped the Timex Sinclair line altogether.
Some companies outside the US and UK produced their own "pirate" versions of the ZX81 and Timex Sinclair computers, aided by weak intellectual property laws in their countries of origin. Several Brazil
ian companies produced ZX81 clones, notably the TK series (such as the TK 85
) from Microdigital Eletronica
of Brazil) and Prológica's CP-200. Czerweny Eletronica of Argentina produced the CZ1000 and CZ1500, clones of the ZX81 and TS1500 respectively. Lambda Electronics of Hong Kong produced the Lambda 3000, based on the ZX81, which was itself widely copied by other Chinese manufacturers.
The machines were not all straight copies of the ZX81; some, such as the CP-200, came with extra memory and a larger case (often with a chiclet keyboard
in place of the original membrane keyboard). One clone, the TL801 from TELLAB of Italy, could emulate either the ZX80 or ZX81 and switch between the two machines via a jumper.
and the Young Businessman of the Year award in 1983.
The machine also had a widespread and lasting social impact in the United Kingdom. According to Clive Sinclair, purchasers of the ZX81 came from "a reasonably broad spectrum" that ranged from readers of the upmarket Observer and Sunday Times newspapers to the more downmarket but numerous Sun readers. The largest age group was around 30 years old. The Financial Times reported in March 1982 that most Sinclair computers were being bought for educational purposes, both for adults and children, though the children were usually able to learn much more quickly. Ian Adamson and Richard Kennedy note that the popularity of the ZX81 was "subtly different from the run-of-the-mill social fad"; although most enthusiasts were in their teens or early twenties, many were older users – often parents who had become fascinated by the ZX81s that they had bought for their children. On the downside, the ZX81 boom was overwhelmingly male-dominated.
One of the ZX81's key legacies was that it spurred huge numbers of people to try programming for the first time. This gave the UK a computing culture that was perhaps unequalled anywhere else and gave rise to a generation of expert programmers. The ZX81 plays a significant part in the plot of William Gibson
's 2003 novel Pattern Recognition
. One character, an artist using old ZX81s as a sculptural medium, explains the cultural and intellectual impact that the machine had on British society:
Among those whose first experience of home computing was provided by the ZX81 are Terry Pratchett
(who used it for "very primitive word processing"), Edward de Bono
and – perhaps proving William Gibson's point – many video game developer
s including Charles Cecil
, Raffaele Cecco
, Pete Cooke
, David Perry (whose first published game, a driving game, involved "a black blob avoiding other black blobs"), Rhianna Pratchett
, and Jon Ritman
.
Even though 2011 has seen the 30th anniversary of the ZX81, its legacy continues with active user forums in German and in English.
New hardware and software continues to be developed for the ZX81, including:
Home computer
Home computers were a class of microcomputers entering the market in 1977, and becoming increasingly common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single nontechnical user...
produced by Sinclair Research and manufactured in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
by Timex Corporation
Timex Corporation
Timex Group USA, Inc. , a subsidiary of Timex Group B.V. and its US headquarters, is based in Middlebury, Connecticut...
. 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. It was hugely successful and more than 1.5 million units were sold before it was eventually discontinued. The ZX81 found commercial success in many other countries, notably the United States, where Timex manufactured and distributed it under licence. Timex later produced its own versions of the ZX81 for the US market – the Timex Sinclair 1000
Timex Sinclair 1000
The Timex Sinclair 1000 was the first computer produced by Timex Sinclair, a joint-venture between Timex Corporation and Sinclair Research. It was launched in July 1982....
and Timex Sinclair 1500. Unauthorised clones of the ZX81 were produced in a number of countries.
The ZX81 was designed to be small, simple, and above all cheap, using as few components as possible to keep the cost down. Video output was to a television set rather than a dedicated monitor. Programs and data were loaded and saved onto audio tape cassettes. It had only four silicon chips on board and a mere 1 kB of memory. The machine had no moving parts – not even a power switch – and used a touch-sensitive membrane keyboard
Membrane keyboard
A membrane keyboard is a computer keyboard whose "keys" are not separate, moving parts, as with the majority of other keyboards, but rather are pressure pads that have only outlines and symbols printed on a flat, flexible surface...
for manual input. The ZX81's limitations prompted the emergence of a flourishing market in third-party peripherals to improve its capabilities. Such limitations, however, achieved Sinclair's objective of keeping the cost of the machine as low as possible. Its distinctive design won awards in the UK and abroad.
The ZX81 could be bought by mail order in kit form or pre-assembled. In what was then a major innovation, it was the first cheap mass-market home computer that could be bought from high street
High Street
High Street, or the High Street, is a metonym for the generic name of the primary business street of towns or cities, especially in the United Kingdom. It is usually a focal point for shops and retailers in city centres, and is most often used in reference to retailing...
stores, led by W.H. Smith and soon many other retailers. The ZX81 marked the first time that computing in Britain became an activity for the general public, rather than the preserve of businesspeople and electronics hobbyists. It inspired the creation of a huge community of enthusiasts, some of whom founded their own businesses producing software and hardware for the ZX81. Many went on to play a major role in the British computer industry in later years. 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
Clive Sinclair
Sir Clive Marles Sinclair is a British entrepreneur and inventor, most commonly known for his work in consumer electronics in the late 1970s and early 1980s....
.
Features
The ZX81 came with 1 kBKilobyte
The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...
of on-board memory that could be expanded externally to 16 kB. Its single circuit board is housed inside a wedge-shaped plastic case measuring 167 millimetres (6.6 in) deep by 40 millimetres (1.6 in) high. The memory is provided by either a single 4118 (1024 Bit × 8) or two 2114 (1024 Bit × 4) RAM chips. There are only three other chips on board: a 3.5 MHz Z80A 8-bit
8-bit
The first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M operating system. The Zilog Z80 and the Motorola 6800 were also used in similar computers...
microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
from Nippon Electric (now NEC
NEC
, a Japanese multinational IT company, has its headquarters in Minato, Tokyo, Japan. NEC, part of the Sumitomo Group, provides information technology and network solutions to business enterprises, communications services providers and government....
), an uncommitted logic array
Gate array
A gate array or uncommitted logic array is an approach to the design and manufacture of application-specific integrated circuits...
(ULA) chip from Ferranti
Ferranti
Ferranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. Known primarily for defence electronics, the Company was once a constituent of the FTSE 100 Index but ceased trading in 1993.The...
and a 8 kB ROM providing a simple BASIC
BASIC
BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....
interpreter. The entire machine weighs just 350 grams (12.3 oz). The memory can be expanded externally to a maximum of 16 kB. Early versions of the external cartridge contained 15 kB of memory using an assortment of memory chips, while later versions contained 16 kB of chips but the lowest addressed kilobyte was disabled.
The front part of the case is occupied by an integrated 40-key membrane keyboard displaying 20 graphic and 54 inverse video characters. Each key has up to five functions, accessed via the SHIFT and FUNCTION keys or depending on context. For example, the P key combined the letter 'P', the " character and the BASIC commands PRINT and TAB. The ZX81 uses a standard QWERTY
QWERTY
QWERTY is the most common modern-day keyboard layout. The name comes from the first six letters appearing in the topleft letter row of the keyboard, read left to right: Q-W-E-R-T-Y. The QWERTY design is based on a layout created for the Sholes and Glidden typewriter and sold to Remington in the...
keyboard layout
Keyboard layout
A keyboard layout is any specific mechanical, visual, or functional arrangement of the keys, legends, or key–meaning associations of a computer, typewriter, or other typographic keyboard....
, with some extra keys that are unfamiliar to modern eyes, such as a RUBOUT key (instead of DELETE) and a NEW LINE key rather than RETURN or ENTER. The keyboard is mechanically very simple, consisting of 40 pressure-pad switches and eight diodes under a plastic overlay, connected in a matrix of eight rows and five columns.
The ZX81's primary input/output is delivered via four sockets on the left side of the case. The machine uses an ordinary UHF television set to deliver a monochrome picture via a built-in RF modulator. It can display 24 lines of 32 characters each, and by utilising the selection of 2x2 block character graphics
Text semigraphics
Text semigraphics is a primitive method used in early video hardware to emulate per pixel addressable graphics without having to implement the logic for a true "high resolution" mode....
from the machine's character set offered an effective 64 × 44 pixel graphics mode, also directly addressible via BASIC using the PLOT and UNPLOT commands. Two 3.5 mm jacks connect the ZX81 to the EAR (output) and MIC (input) sockets of an audio cassette recorder, enabling data to be saved or loaded at a rate of 250 baud
Baud
In telecommunications and electronics, baud is synonymous to symbols per second or pulses per second. It is the unit of symbol rate, also known as baud rate or modulation rate; the number of distinct symbol changes made to the transmission medium per second in a digitally modulated signal or a...
. This provides a somewhat temperamental storage medium for the machine, which has no built-in storage capabilities. The ZX81 requires 420 mA of power at 7–11 V
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
DC
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
, delivered via a custom 9 V Sinclair DC power supply.
The ULA chip, described by the ZX81 manual as the "dogsbody" of the system, has a number of key functions that competing computers shared between multiple chips and integrated circuits. These comprise:
- Synchronising the screen display;
- Generating a 6.5 MHz clock, from which a 3.25 MHz clock is derived for the processor;
- Outputting an audio signal to a cassette recorder in SAVE mode;
- Processing the incoming cassette audio signal in LOAD mode;
- Sensing keystrokes;
- Using memory addresses provided by the CPU to decide when ROM and RAM should be active;
- Controlling general system timing.
The ZX81's built-in RF modulator
RF modulator
An RF modulator is a device that takes a baseband input signal and outputs a radio frequency-modulated signal....
can output a video picture to either a UHF 625 line colour or monochrome television (used in the UK, Australia, and most western European countries). France required a slightly modiified version of the machine to match the positive video modulation of their sets. The USA and Canada required a different ULA chip and modulator to cope with their 525 line VHF television systems. Both the ZX81 and its predecessor, the ZX80, have a significant drawback in the way that they handle visual output. Neither machine has enough processing power to run at full speed and simultaneously maintain the screen display. On the ZX80, this means that the screen goes blank every time the machine carries out a computation and causes an irritating flicker whenever a shorter computation – such as processing a keystroke – takes place.
Another hardware quirk produced one of the most distinctive aspects of the ZX81's screen display – during loading or saving, moving zigzag stripes appear across the screen. The same pin on the ULA is used to handle the video signal as well as the tape output, producing the stripes as an interference pattern of sorts. As well as this, the ULA cannot maintain the display during SAVE and LOAD operations, as it has to operate continuously to maintain the correct baud rate for data transfers.
The unexpanded ZX81's tiny memory presented a major challenge to programmers. Simply displaying a full screen takes up 768 bytes, the system variables take up another 125 bytes and the program, input buffer and stacks need more memory on top of that. Nonetheless, ingenious programmers were able to achieve a surprising amount with just 1 kB. One notable example was 1K ZX Chess
1K ZX Chess
1K ZX Chess is a chess-playing computer program for the unexpanded Sinclair ZX81, created by programmer David Horne. The game implements most chess rules , artificial intelligence, and a user interface...
by David Home, which is somewhat misnamed as it managed to squeeze most of the rules of chess into just 672 bytes. The ZX81 conserved 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
ASCII
The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
) character set.
The edge connector or external interface at the rear of the ZX81 is an extension of the main printed circuit board. This provides a set of address, control, and data lines that can be used to communicate with external devices. Enthusiasts made use of this facility to create a wide range of add-ons for the ZX81.
Comparisons between ZX81 and other computing devices
The following table provides a comparison between the capabilities of the ZX81 and various other competing microcomputers that were already on the market at the time of the ZX81's launch. The prices given are as of December 1982. To illustrate how far computing devices have come since then, it also compares the Apple iPhone 4IPhone 4
The iPhone 4 is a touchscreen slate smartphone developed by Apple Inc. It is the fourth generation iPhone, and successor to the iPhone 3GS. It is particularly marketed for video calling , consumption of media such as books and periodicals, movies, music, and games, and for general web and e-mail...
as an example of a modern device that costs about the same in real terms as a ZX81 did in 1981 but is far smaller.
| Device | RAM standard | Expandable to | CPU | Storage | Upper- and lower case |
List price | Number of colours |
Maximum resolution |
Sound |
|---|---|---|---|---|---|---|---|---|---|
| Apple II Plus Apple II Plus The Apple II Plus was the second model of the Apple II series of personal computers produced by Apple Computer, Inc. It was sold new from June 1979 to December 1982.-Features:... |
16 kB | 48 kB | MOS Technology 6502 @ 1 MHz | Cassette tape / floppy disk (up to 143 kB per drive) | No | $1330 | 16 | 280 × 194 pixels | Clicks via speaker |
| Atari 800 | 16 kB | 48 kB | MOS Technology 6502 @ 1.78 MHz | Cassette tape / floppy disk (up to 92 kB per drive) | Yes | $899.95 | 256 | 320 × 192 pixels | 4-voice / 4-octave effects |
| Commodore PET Commodore PET The Commodore PET was a home/personal computer produced from 1977 by Commodore International... |
16 or 32 kB | 32 kB | MOS Technology 6502 @ 1 MHz | Cassette tape / floppy disk (up to 1024 kB per drive) | Yes | $995 | monochrome | 80 × 50 pixels | 1 voice / 3 octaves |
| Commodore VIC-20 Commodore VIC-20 The VIC-20 is an 8-bit home computer which was sold by Commodore Business Machines. The VIC-20 was announced in 1980, roughly three years after Commodore's first personal computer, the PET... |
5 kB | 32 kB | MOS Technology 6502 @ 1.02 MHz | Cassette tape / floppy disk (up to 170 kB per drive) | Yes | $260 | 16 | 176 × 184 pixels | 3 voices / white noise |
| IBM PC IBM PC The IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981... |
16 kB | 512 kB | Intel 8088 @ 4.77 MHz | Cassette tape / floppy disk (up to 320 kB per drive) | Yes | $1265 | 16 | 640 × 200 pixels | 1 voice |
| Radio Shack TRS-80 III TRS-80 TRS-80 was Tandy Corporation's desktop microcomputer model line, sold through Tandy's Radio Shack stores in the late 1970s and early 1980s. The first units, ordered unseen, were delivered in November 1977, and rolled out to the stores the third week of December. The line won popularity with... |
16 kB | 48 kB | Zilog Z80 @ 1.78 MHz | Cassette tape / floppy disk (up to 175 kB per drive) | Yes | $699 | Monochrome | 128 × 96 pixels | Basic sound via cassette interface |
| Texas Instruments TI-99/4A Texas Instruments TI-99/4A The Texas Instruments TI-99/4A was an early home computer, released in June 1981, originally at a price of USD $525. It was an enhanced version of the less-successful—and quite rare—TI-99/4 model, which was released in late 1979 at a price of $1,150... |
16 kB | 48 kB | TI TMS9900 @ 3.0 MHz | Cassette tape / floppy disk (up to 90 kB per drive) | Yes | $299 | 16 | 256 × 192 pixels | 3 voices / white noise |
| ZX81 / TS1000 | 1 kB / 2 kB | 64 kB | Zilog Z80 @ 3.25 MHz or NEC Z80 @ 3.25 MHz | Cassette tape | No | $99.95 | Monochrome | 64 x 44 pixels | None |
| Apple iPhone 4 | 524,288 kB | n/a | ARM Cortex-A8 Apple A4 @ ~750 Mhz | 16,777,216 – 33,554,432 kB flash memory | Yes | $649.00 - $749.00 | 16,777,216 | 960 × 640 pixels | Full stereo audio |
Background
Amplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
s, radios, multimeter
Multimeter
A multimeter or a multitester, also known as a VOM , is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter may include features such as the ability to measure voltage, current and resistance...
s and other items generally sold in kit form to hi-fi enthusiasts and other electronics hobbyists. The company entered a new market in 1972 when it launched the first "slimline" pocket calculator, the Sinclair Executive
Sinclair Executive
The Sinclair Executive was Clive Sinclair's first venture into the pocket calculator market. The Executive was the world's first "slimline" pocket calculator. It was variously described as "a piece of personal jewelry" and "at once a conversation piece, a rich man's plaything and a functional...
. It was a major success that Radionics followed up by launching a wide range of pocket calculators. The company's subsequent expansion made it Europe's biggest calculator manufacturer by 1975.
By the late 1970s, however, Sinclair Radionics was in serious difficulties. It lost its ability to compete effectively in the calculator market following the launch of a new generation of Japanese-produced calculators with liquid crystal display
Liquid crystal display
A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....
s, which were much more capable and power-efficient than Sinclair's LED
Light-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
calculators. Projects to develop a pocket television and digital watch turned out to be expensive flops. The company made losses of over £350,000 in 1975–76, bringing it to the edge of bankruptcy. In July 1977 Radionics was rescued by a state agency, the National Enterprise Board
National Enterprise Board
-History:The National Enterprise Board was set up in the United Kingdom in 1975 to implement the Wilson Labour government's objective of extending public ownership of industry...
(NEB), which recapitalised it, provided a loan facility and took effective control of the company by acquiring a 73% stake.
Clive Sinclair's relationship with the NEB was fraught due to conflicting notions about which direction the company should go. Radionics had begun a project to develop a home computer but the NEB wanted to concentrate on the instrument side of the business, which was virtually the only area where Radionics was profitable. Sinclair disagreed vehemently with what he characterised as the view "that there was no future in consumer electronics". This and other disputes led to Sinclair resigning from Radionics in July 1979.
While he was struggling with the NEB, Clive Sinclair turned to a "corporate lifeboat" in the shape of an existing corporate shell under his exclusive control – a company called Ablesdeal Ltd, which he had established in 1973 and later renamed Science of Cambridge. It became a vehicle through which he could pursue his own projects, free of the interference of the NEB. Despite his later success in the field, Sinclair saw computers as merely a means to an end. 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
TV80
The Sinclair TV80, also known as the Flat Screen Pocket TV or FTV1, was a pocket television launched by Sinclair Research in 1984. Unlike Sinclair's earlier attempts at a portable television, the TV80 used a flat CRT with a side-mounted electron gun instead of a conventional CRT; the picture was...
pocket television and C5
Sinclair C5
The Sinclair Research C5 is a battery electric vehicle invented by Sir Clive Sinclair and launched by Sinclair Research in the United Kingdom on 10 January 1985. The vehicle is a battery-assisted tricycle steered by a handlebar beneath the driver's knees. Powered operation is possible making it...
electric vehicle. In an interview with Practical Computing, Sinclair explained:
Precursors: the MK14 and ZX80
By the late 1970s, American companies such as Apple were producing simple home computer kits. This aroused interest among electronics hobbyists in the UK but relatively high prices reduced the appeal of the American products. Off-the-shelf personal computers were also available for the high end of the market but were extremely expensive; Olivetti's offering cost £2,000, and the Commodore PET, launched in 1979, sold for £700. There was nothing for the hobbyist at the low end of the market. Sinclair realised that this provided a useful commercial opportunity.Sinclair's first home computer was the MK14
MK14
The Microcomputer Kit 14, or MK14 was a computer kit sold by Science of Cambridge of the United Kingdom, first introduced in 1977 for UK£39.95. The MK14 eventually sold over 50,000 units. It used a National Semiconductor SC/MP CPU , 256 bytes of random access memory which was directly expandable...
, which was launched in kit form in June 1978. It was a long way from being a mass-market product. Its very name – MK standing for "Microcomputer Kit" – was indicative of its origins as a product developed by, and for, hobbyists. It had no screen but instead used an LED segment display (though Science of Cambridge did produce an add-on module allowing it to be hooked up to a UHF TV); it had no case, consisting of an exposed circuit board; it had no built-in storage capabilities and only 256 byte
Byte
The byte is a unit of digital information in computing and telecommunications that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer...
s of memory; and input was via a 20-key hexadecimal
Hexadecimal
In mathematics and computer science, hexadecimal is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F to represent values ten to fifteen...
keyboard. Despite the limitations of the machine it sold a respectable 10–15,000 units; by comparison, the much more expensive Apple II
Apple II
The Apple II is an 8-bit home computer, one of the first highly successful mass-produced microcomputer products, designed primarily by Steve Wozniak, manufactured by Apple Computer and introduced in 1977...
had only sold 9,000 units in the United States, a much bigger market, in 1978. This success convinced Clive Sinclair that there was an untapped market for low-cost computers that could profitably be exploited.
Sinclair followed up the MK14 by producing the ZX80, at the time the world's smallest and cheapest computer, which was launched in January 1980 costing £99.95 (equivalent to £319 at 2009 prices.) The company conducted no market research whatsoever prior to the launch of the ZX80; according to Clive Sinclair, he "simply had a hunch" that the general public was sufficiently interested to make such a project feasible and went ahead with ordering 100,000 sets of parts so that he could launch at high volume.
Rick Dickinson
Rick Dickinson is a British industrial designer.-Early life:Dickinson graduated from Newcastle Polytechnic in 1979 with a First Class Bachelor of Arts Honours degree in Design for Industry. The 'Design for Industry' degree was the first of its kind, formerly a three-year 'Industrial Design' degree...
, a young British industrial design
Industrial design
Industrial design is the use of a combination of applied art and applied science to improve the aesthetics, ergonomics, and usability of a product, but it may also be used to improve the product's marketability and production...
er who had recently been hired by Sinclair. As he later recalled of Sinclair's approach, "Everything was cost driven. The design was the face of the machine." The unconventional keyboard was the outcome of Sinclair's cost-cutting. It made use of a sheet of plastic, on which the keys were printed, overlaying a metallic circuit that registered when a key was pressed. This avoided the expense of providing a typewriter-style keyboard, though the design had many drawbacks when it came to usability and "feel".
Inside the case, there were many more similarities with the ZX81. Like its successor, it used the Z80A microprocessor and had only 1 kB of on-board RAM. It came with a specially written BASIC interpreter on a dedicated ROM chip and could use a television as a display. It relied on an ordinary cassette tape recorder for data storage. The main difference between the two machines lay in the internal software; when the ZX81 was released, ZX80 owners were able to upgrade by the relatively simple expedient of soldering a new ROM onto the circuit board.
The ZX80 was an immediate success, selling 20,000 units over the following nine months. Science of Cambridge was producing ZX80s at the rate of 9,000 a month by the end of 1980 and within 18 months of its launch the company had sold 100,000 units. The commercial success of the ZX80 made a follow-up product inevitable. The company was renamed Sinclair Computers in November 1980, reflecting its new focus, and became Sinclair Research in March 1981.
The BBC Micro affair
The launch of the ZX81 was catalysed in part by the British Broadcasting Corporation's plan to produce a TV seriesThe Computer Programme
The Computer Programme was a TV series, produced by Paul Kriwaczek, originally broadcast by the BBC in 1982. The idea behind the series was to introduce people to computers and show them what they were capable of. The BBC wanted to use their own computer, so the BBC Micro was developed as part of...
, to be broadcast in 1982, aimed at popularising computing and programming. The BBC intended to commission an existing manufacturer to provide it with a BBC-branded home computer to tie in with the series. When Sinclair got wind of the project in December 1980, he wrote to the BBC informing them that he would be announcing a new version of the ZX80, to be called the ZX81, in the spring of 1981. It would remedy some of the ZX80's deficiencies and would be both cheaper and more advanced. Sinclair naturally wanted the ZX81 to be a candidate for the BBC contract and lobbied for its adoption. He pointed out that there were already 40,000 users of the ZX80 and that by the time the series was broadcast there were likely to be upwards of 100,000 ZX81 users (which turned out to be an underestimate by over 400,000 – an indication of how the ZX81's success exceeded even Sinclair's expectations).
A prototype ZX81 was demonstrated to BBC representatives in January 1981, while Sinclair's local rival Acorn Computers
Acorn Computers
Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the UK. These included the Acorn Electron, the BBC Micro, and the Acorn Archimedes...
put forward their proposed Proton computer, a design – of which a prototype did not yet exist – based on the Acorn Atom
Acorn Atom
The Acorn Atom was a home computer made by Acorn Computers Ltd from 1980 to 1982 when it was replaced by the BBC Micro and later the Acorn Electron....
. To Sinclair's dismay, the contract to produce the BBC Microcomputer went to Acorn, which launched the machine in January 1982. Paul Kriwaczek, the producer of The Computer Programme, explained his reservations in a March 1982 interview with Your Computer
Your Computer (British magazine)
Your Computer was a British computer magazine published monthly from 1981 to 1988, and aimed at the burgeoning home computer market. At one stage it was, in its own words, "Britain's biggest selling home computer magazine". It offered support across a wide range of computer formats, and included...
:
Sinclair was bitterly critical of the BBC's decision, accusing it of incompetence and arrogance. Shortly after Acorn won the BBC contract the Government issued a recommended list of computers that schools could purchase, with the aid of a grant, for half price. Sinclair's computers were not included on the list. Sinclair responded by launching his own half-price deal, offering schools the chance to buy a ZX81 and 16 kB RAM pack for £60, plus a ZX Printer at half price, for a total cost of £90. As the cheapest Government-approved system was £130, this was an attractive offer for many schools and about 2,300 bought Sinclair's package.
Development and manufacture
Jim Westwood
Jim Westwood was the chief engineer at Sinclair Research Ltd in the 1980s, starting at the company in 1963. Westwood was the technical mastermind behind many of Sinclair's products and worked there for more than twenty years...
, was given the task of improving the ZX80's hardware to reduce the number of components and thus bring down the cost. He also sought to fix some of the more annoying problems with the ZX80. Westwood and his colleagues found that the component count could be reduced greatly by combining eighteen of the ZX80's chips into a single uncommitted logic array (ULA), a type of general-purpose chip that allowed manufacturers to reprogram it to meet their particular requirements rather than having to develop their own customised chip at greater expense. Ferranti
Ferranti
Ferranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. Known primarily for defence electronics, the Company was once a constituent of the FTSE 100 Index but ceased trading in 1993.The...
produced the new chip for Sinclair, who hailed Westwood's design as a triumph of innovation: "The ZX81 had four chips when our nearest competitor in this respect, the TRS-80, had 44." Only 70% of the logic gates on the ULA were supposed to be used, but Sinclair decided to obtain maximum benefit by using them all. This resulted in the machine becoming uncomfortably warm during usage. Computing folklore held that the ZX81 had to be refrigerated by balancing a carton of cold milk on top of the case.
The ZX81's ROM was doubled to 8 kB, from the ZX80's 4 kB ROM. This enabled a fuller implementation of a version of ANSI Minimal BASIC (termed Sinclair BASIC
Sinclair BASIC
Sinclair BASIC is a dialect of the BASIC programming language used in the 8-bit home computers from Sinclair Research and Timex Sinclair...
by the company). Clive Sinclair re-commissioned a company called Nine Tiles, which had produced the ZX80 ROM, to develop the new ROM software for the ZX81. The code was written by John Grant, the owner of Nine Tiles, and Steve Vickers, who had joined the company in January 1980. Grant concentrated on the software that drove the ZX81's hardware, while Vickers developed the new BASIC and the accompanying manual. Sinclair's brief to the pair was fairly non-specific but primarily concerned remedying a key defect of the ZX80 so that the new machine could be used for practical programming and calculations. Vickers later recalled:
The new ROM incorporated trigonometric
Trigonometry
Trigonometry is a branch of mathematics that studies triangles and the relationships between their sides and the angles between these sides. Trigonometry defines the trigonometric functions, which describe those relationships and have applicability to cyclical phenomena, such as waves...
and floating point
Floating point
In computing, floating point describes a method of representing real numbers in a way that can support a wide range of values. Numbers are, in general, represented approximately to a fixed number of significant digits and scaled using an exponent. The base for the scaling is normally 2, 10 or 16...
functions, which its predecessor had lacked – the ZX80 could only deal with whole numbers. Grant came up with one of the ZX81's more novel features, a syntax checker that indicated errors in BASIC code as soon as it was entered (rather than, as was standard at the time, only disclosing coding errors when a program was run). 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
ZX Printer
The Sinclair ZX Printer is a spark printer which was produced by Sinclair Research for its ZX81 home computer. It was launched in 1981, with a recommended retail price of £49.95....
code into the ROM. Although it was eventually fixed, the bug became the subject of controversy and Sinclair was forced to replace some of the ZX81s sold to early customers. On a more positive note, Vickers' work on the manual was received favourably, being described in 1983 as "one of the classic texts on BASIC". Max Phillips commented in a What Micro? retrospective:
The task of designing the ZX81's case again fell to Rick Dickinson, who produced an updated version of the ZX80's wedge-shaped case. This time round, the design team were able to use injection moulding
Injection moulding
Injection molding is a manufacturing process for producing parts from both thermoplastic and thermosetting plastic materials. Material is fed into a heated barrel, mixed, and forced into a mold cavity where it cools and hardens to the configuration of the cavity...
, which enabled them to deliver a higher-quality case. Dickinson originally envisaged the ZX81 as "an expandable range of boxes following a vaguely modular approach with a common width", though this approach was eventually dropped. From start to finish, the design process took about six months.
The ZX81 was launched on 5 March 1981 in two versions (though with identical components) – a pre-assembled machine or a cheaper kit version, which the user could assemble himself. Both versions were manufactured in Dundee
Dundee
Dundee is the fourth-largest city in Scotland and the 39th most populous settlement in the United Kingdom. It lies within the eastern central Lowlands on the north bank of the Firth of Tay, which feeds into the North Sea...
, Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
by Timex Corporation
Timex Corporation
Timex Group USA, Inc. , a subsidiary of Timex Group B.V. and its US headquarters, is based in Middlebury, Connecticut...
at the company's Dryburgh
Dryburgh (Dundee district)
Dryburgh is the name of a district of Dundee, Scotland, home to The View. The band featured locations throughout the area in their video for their 2006 track Superstar Tradesman. The Dryburgh estate has been used for the band's 2007 videos for Skag Trendy and The Don...
factory. Timex had not been an obvious choice of manufacturing subcontractor, as the company had little previous experience in assembling electronics. It was a well-established manufacturer of mechanical watches but was facing a crisis at the beginning of the 1980s. Profits had dwindled to virtually zero as the market for mechanical watches stagnated in the face of competition from the digital and quartz watches. Recognising the trend, Timex's director, Fred Olsen
Fredrik Olsen
Thomas Fredrik Olsen or Fred Olsen is a Norwegian shipping magnate and Chairman of the companies in the Fred. Olsen Group. He is the fourth generation running the Fred. Olsen Group, founded by his great grandfather Petter Olsen and named after his grandfather Thomas Fredrik Olsen...
, determined that the company would diversify into other areas of business.
This shift by Timex came at an ideal time for Sinclair. The ZX80 had proved more popular than expected and Sinclair's existing manufacturer, a small electronics company in St Ives
St Ives, Cambridgeshire
St Ives is a market town in Cambridgeshire, England, around north-west of the city of Cambridge and north of London. It lies within the historic county boundaries of Huntingdonshire.-History:...
, lacked the resources to deal with the demand. Timex took over production of the ZX80 late in 1980. The arrangement worked well for both companies and Timex took on the manufacture of the ZX81, aided by capital investment in its Dundee plant. Sinclair initially planned to produce 10,000 ZX81s a month, rising to 30,000 a month within a year. However, Timex initially had significant problems in producing enough ZX81s to satisfy demand. As a consequence, it took up to nine weeks for ZX81s to be delivered by mail order. It was not until September 1981, five months after the launch of the ZX81, that the delivery times finally came down to the promised twenty-eight days. Those who already owned or had recently ordered the ZX80 were not left out in the cold. Anyone who had ordered a ZX80 in the two weeks before the ZX81's launch would receive the newer machine, while existing owners were able to upgrade their ZX80s by soldering an extra £20 ROM chip into the circuit board.
The reliability of the ZX81 was a somewhat controversial issue. W.H. Smith, one of the machine's key distributors, had a company policy of ordering a third more ZX81s than were actually required for sale, so that it would have enough replacements for faulty machines. Similar problems were reported in the US market, where contemporary reports suggested that only a third of the ZX81s shipped actually worked. However, figures released by Sinclair claimed that only 2.4 per cent of pre-assembled machines were returned, although 13 per cent of kits were returned. Clive Sinclair strongly denied any problem with reliability:
The higher failure rate of the kits was put down to customers breaking the components by inserting or soldering them the wrong way, though Sinclair admitted that there was a persistent problem with power supplies that affected both kits and pre-assembled ZX81s. The bigger problem was perhaps Sinclair's after-sales service, or rather the lack thereof, which Robin Clarke of New Scientist
New Scientist
New Scientist is a weekly non-peer-reviewed English-language international science magazine, which since 1996 has also run a website, covering recent developments in science and technology for a general audience. Founded in 1956, it is published by Reed Business Information Ltd, a subsidiary of...
described as "one of the worst after-sales performance records of any company ever established." The Financial Times observed that "Clive Sinclair's offices are filled with returned computers which can take months to be repaired." The company's slowness in replacing returns and delivering freshly ordered machines meant that Sinclair Research gained an unenviable reputation for poor customer service.
Marketing
The marketing of the ZX81 was handled by Sinclair's long-standing marketing agency Primary Contact (now part of Ogilvy & MatherOgilvy & Mather
Ogilvy & Mather is an international advertising, marketing and public relations agency based in Manhattan and owned by the WPP Group. The company operates 497 offices in 125 countries with approximately 16,000 employees.-History:...
), which had provided marketing services for Sinclair since 1971 and was to continue doing so until 1985. Sinclair's entry into the nascent home computing market gave Primary Contact a major challenge – how to market a product simultaneously at hobbyists and at the "man on the street", who probably had little or no computer literacy. The answer was to pursue what the journalist David O'Reilly of MicroScope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...
magazine described as a single-minded "user-friendly strategy." Chris Fawkes, one of Primary Contact's directors, explained: "We brought personal computers to the mass market by showing that you didn't have to be a whizzkid to use one." As Clive Sinclair put it in a 1982 interview with Your Computer,
According to the US market analyst Ben Rosen, by pricing the ZX81 so low, "Sinclair has opened up a completely new market among people who had never previously considered owning a computer." Clive Sinclair acknowledged the role that guesswork had played in his decision to launch the ZX81 on such a large scale: "It was a surmise that the man in the street would want such a computer. He does, and our information is that a lot of people are using the machines avidly." A New Scientist retrospective published in 1986 commented:
High-profile advertising was central to the marketing campaign. Although Sinclair Research was a relatively small company, it had a long-standing policy of using large-scale advertisements that stood out in stark contrast to the more muted advertisements of other manufacturers. Superlatives, exhortations, appeals to patriotism, testimonials, eye-catching drawings and photographs on double-page spreads, varying from month to month, were used to drum up mail order business for Sinclair. The launch advertising for the ZX81 illustrates this approach. A photograph of the ZX81 alongside the official Sinclair peripherals dominated the centre of a double-page spread. The value for money of Sinclair's products was emphasized by the prices being printed in larger type than any other text on the spread. The ZX81's benefits were promoted with the aspirational slogan "Sinclair ZX81 Personal Computer – the heart of a system that grows with you". The advertisement highlighted ZX81 BASIC Programming, the manual written by Steve Vickers, as "a complete course in BASIC programming, from first principles to complex programs." The educational benefits of the ZX81 were stressed ("it's still very simple to teach yourself computing") and its technical advantages were explained in relatively non-technical terms. For instance, the ZX81's idiosyncratic method of typing commands with a single keystroke – the result of the memory-saving method of using one-byte tokens to represent keywords – was presented as "eliminat[ing] a great deal of tiresome typing". The ZX81's British character was emphasized; it was "designed by Sinclair and custom-built in Britain." Sinclair's advertising in the United States provides an illustration of how the company perceived the ZX81's purpose:
This approach to advertising was driven by Sinclair's reliance on mail-order marketing. It came with a high up-front cost in terms of purchasing space in publications but it had the advantage of ensuring that all sales were firm and pre-paid. A big splash on launch produced a large influx of cash at the outset of a campaign, though it did also depend on the advertiser having enough product to satisfy the initial surge in demand. The advertisements served an additional purpose of priming the market for over-the-counter sales by "getting the story across", as Clive Sinclair put it: "Not that big a proportion do buy on mail order, but they see the ads, and that helps to prepare them for buying when the item appears in the shops."
Sinclair himself became a focal point for the marketing campaign, putting a human face on the business, while Sinclair Research was portrayed in the media as a plucky British challenger taking on the technical and marketing might of giant American and Japanese corporations. As David O'Reilly noted, "by astute use of public relations, particularly playing up his image of a Briton taking on the world, Sinclair has become the best-known name in micros." The popular press soon latched onto the image. His "Uncle Clive" persona is said to have been created by the gossip columnist for Personal Computer World
Personal Computer World
Personal Computer World was a long-running British Computer magazine.Although for at least the last decade it contained a high proportion of Windows PC content , the magazine's title was not intended as a specific reference to this...
, while the media praised Sinclair as a visionary genius (or even, in the words of The Sun, "the most prodigious inventor since Leonardo
Leonardo da Vinci
Leonardo di ser Piero da Vinci was an Italian Renaissance polymath: painter, sculptor, architect, musician, scientist, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist and writer whose genius, perhaps more than that of any other figure, epitomized the Renaissance...
.") As Ian Adamson and Richard Kennedy put it, Sinclair outgrew "the role of microcomputer manufacturer and accepted the mantle of pioneering boffin
Boffin
In the slang of the United Kingdom, boffins are scientists, medical doctors, engineers, and other people engaged in technical or scientific research.-Origin:...
leading Britain into a technological utopia."
Pricing was central to the marketing strategy, as it had been through Sinclair's career. The ZX81 had been designed to meet a £70 price point and was launched at a price of £69.95 (built) or £49.95 (kit). One Sinclair brochure presented a side-by-side comparison of the ZX81 with the four machines that Sinclair considered its main rivals – the Acorn Atom
Acorn Atom
The Acorn Atom was a home computer made by Acorn Computers Ltd from 1980 to 1982 when it was replaced by the BBC Micro and later the Acorn Electron....
, Apple II Plus
Apple II Plus
The Apple II Plus was the second model of the Apple II series of personal computers produced by Apple Computer, Inc. It was sold new from June 1979 to December 1982.-Features:...
, Commodore PET
Commodore PET
The Commodore PET was a home/personal computer produced from 1977 by Commodore International...
and TRS-80
TRS-80
TRS-80 was Tandy Corporation's desktop microcomputer model line, sold through Tandy's Radio Shack stores in the late 1970s and early 1980s. The first units, ordered unseen, were delivered in November 1977, and rolled out to the stores the third week of December. The line won popularity with...
. The comparison highlighted the vast differences in cost, from £630 in the case of the Apple II Plus to just £70 for the ZX81, though even by Sinclair's own comparison the Apple was by far the more capable machine.
According to Sinclair himself, the £69.95 price was chosen after applying the "experience curve" developed by the Boston Consulting Group
Boston Consulting Group
The Boston Consulting Group is a global management consulting firm with offices in 42 countries. It is recognized as one of the most prestigious management consulting firms in the world. It is one of only three companies to appear in the top 15 of Fortunes "Best Companies to Work For" report for...
. Sinclair's prior experience in the calculator market had highlighted the fact that a product will be more profitable selling at (for instance) twice the manufactured cost than at three times. He could have launched the ZX81 at a higher price, marketing it in a more traditional way as a premium product, but chose not to. In effect, he used the lower price to establish an unassailable lead before the competition moved in.
An essential part of Sinclair's marketing strategy was to use regular cost-cutting at strategic intervals to maintain market share. Ian Adamson and Richard Kennedy comment that Sinclair's approach was "to secure and extend [his] market lead and panic the competition. While most companies reduce prices when their products are in steep decline, Sinclair tends to discount shortly after sales have peaked. The advantage of his approach is that vacillating customers are drawn into the fold while the product's promotion retains a commercial urgency, and the costings of the competition are thrown into utter disarray."
This tactic proved highly successful. When sales of the ZX81 fell in the wake of the launch of its successor, the ZX Spectrum
ZX Spectrum
The ZX Spectrum is an 8-bit personal home computer released in the United Kingdom in 1982 by Sinclair Research Ltd...
, Sinclair reduced the price of the pre-assembled version to £49.95 in May 1982. It was cut by another £10 the following April. Despite the increased competition from much more capable computers, the ZX81 was still shipping in excess of 30,000 units a month even as late as July 1983, more than two years after it had been launched. By that time, over 1.5 million ZX81s had been sold.
Distribution
The ZX81's distribution arrangements were an essential part of its success and marked a watershed in the way that computers were sold in the UK. Sinclair had previously made its name as a mail-order retailer – the ZX81 was initially available only through mail-order – but the only truly effective way to reach the mass market was via high street stores. Fortunately for Sinclair, an opportunity to do just that was provided by W.H. Smith, a venerable book- and magazine-seller and stationery chain. The company had stagnated in the 1970s and was looking for ways to revitalise its image and expand its product range.Smith's had begun selling audio and photographic equipment and calculators at the end of the 1970s, with a modest degree of success. In 1980 its marketing development manager, John Rowland, hit upon the idea of creating "Computer Know-How" sections in major branches to sell computer books and magazines. Most of the items on display were imports from the United States but their relatively high cost reduced their attractiveness to the casual buyer. The commercial success and mass market potential of the ZX80 caught Rowland's interest; he approached Sinclair, saw a prototype ZX81 and agreed to market the machine through Smith's on an exclusive basis for the first six months after launch. As Rowland put it, "what we've done now is bring the computer-orientated publications together with an actual computer, to create the Computer Know-How section of the store", alongside computer software and blank cassette tapes. The ZX81 would be sold in 112 stores around the UK and would serve as the centrepiece of the "Computer Know-How" sections.
Selling the ZX81 over the counter was seen as something of a gamble and Rowland's colleagues were initially unenthusiastic about the scheme. Branch buyers thought that the ZX81 was unlikely to sell more than 10–15 units per branch at launch. Rowland himself thought that the ZX81 would sell about 10,000 units during the first five months of the retail agreement, equivalent to one month's mail order sales by Sinclair. In the event, the ZX81 was a massive success for Smith's. The "Computer Know-How" sections were swamped with eager customers, overwhelming the 300 staff who had been trained to demonstrate the machines; a Financial Times correspondent wrote of being "dazed and bewildered by the crowds of schoolchildren clustered round the ZX81 in your local branch of W.H. Smith." Within a year, Smith's had sold 350,000 ZX81s, making an estimated net profit of £10 million. Sales of peripherals, software, books and magazines netted even more profit.
Other distributors soon joined the act. The British chain stores Boots, John Menzies
John Menzies
John Menzies plc is a Scottish business established in 1833. It has two main divisions: Menzies Distribution and Menzies Aviation. Menzies Distribution is a major distributor of newspapers and magazines throughout the United Kingdom...
and Currys
Currys
Currys is an electrical retailer in the United Kingdom and Ireland and is owned by Dixons Retail plc. It specialises in selling home electronics and household appliances, with 295 superstores and 73 high street stores...
began selling the ZX81 as soon as Smith's exclusive distribution deal expired and a number of companies secured overseas distribution rights for the ZX81, which was being sold in 18 countries by March 1982. Sinclair launched the ZX81 in the United States in November 1981 at a price of $149.95 assembled and $99.95 in kit form, initially selling directly to the American market by mail order. Sales reached 15,000 a month by January 1982, while American Express
American Express
American Express Company or AmEx, is an American multinational financial services corporation headquartered in Three World Financial Center, Manhattan, New York City, New York, United States. Founded in 1850, it is one of the 30 components of the Dow Jones Industrial Average. The company is best...
sold thousands more to its own customers. In February 1982 Timex obtained a licence from Sinclair to sell the ZX81 directly through thousands of retail outlets in the US, paying Sinclair Research a 5 per cent royalty on all Sinclair hardware and software sold by Timex. The company was later to produce its own licensed clones and variants of the ZX81. In December 1981 Mitsui
Mitsui
is one of the largest corporate conglomerates in Japan and one of the largest publicly traded companies in the world.-History:Founded by Mitsui Takatoshi , who was the fourth son of a shopkeeper in Matsusaka, in what is now today's Mie prefecture...
obtained rights to distribute the ZX81 in Japan, selling it by mail order for ¥
Japanese yen
The is the official currency of Japan. It is the third most traded currency in the foreign exchange market after the United States dollar and the euro. It is also widely used as a reserve currency after the U.S. dollar, the euro and the pound sterling...
38,700 (equivalent to £83 in 1982 prices), and had sold 5,000 units by July 1982. The Japanese market's favourable reaction to the ZX81 led Mitsui to begin selling the ZX81 over the counter in large bookshops from September 1982, with annual sales of 20,000 units predicted.
The ZX81 was also sold for a while in duty-free shop
Duty-free shop
Duty-free shops are retail outlets that are exempt from the payment of certain local or national taxes and duties, on the requirement that the goods sold will be sold to travelers who will take them out of the country...
s at UK airports. However, this fell foul of government export restrictions aimed at preventing the Soviet bloc countries from obtaining Western high technology goods. It was not uncommon for visitors from the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
and other eastern European countries to pick up gadgets in Western countries with the aim of transferring their technology
Technology transfer
Technology Transfer, also called Transfer of Technology and Technology Commercialisation, is the process of skill transferring, knowledge, technologies, methods of manufacturing, samples of manufacturing and facilities among governments or universities and other institutions to ensure that...
to their own states' industries. In 1983 the government ordered that the ZX81s were to be withdrawn from sale at airports. There was no such restriction on sales to communist China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
and in November 1983 Sinclair Research announced that it had signed an agreement to export ZX81 kits to a factory in Guangzhou
Guangzhou
Guangzhou , known historically as Canton or Kwangchow, is the capital and largest city of the Guangdong province in the People's Republic of China. Located in southern China on the Pearl River, about north-northwest of Hong Kong, Guangzhou is a key national transportation hub and trading port...
, where they would be assembled for the Chinese market.
In the Netherlands, the regular Sinclair ZX81 was for sale as well as a Bang & Olufsen
Bang & Olufsen
Bang & Olufsen is a Danish company that designs and manufactures audio products, television sets and telephones. It was founded in 1925 by Peter Bang and Svend Olufsen, whose first significant product was a radio that worked with alternating current, when most radios were run from batteries...
branded version called Beocomp.
Reception
Reviews of the ZX81 highlighted the great value for money offered by the machine but noted its technical shortcomings. As Tim HartnellTim Hartnell
Tim Hartnell was an Australian journalist, self-taught programmer and extremely prolific, bestselling author of books and magazines on computer games. His company, Interface Publications , produced titles for all of the machines in the home computer market, including Sinclair machines...
put it in Your Computer, "the ZX81 is both a delight and a disappointment". He applauded the improvements that had been made over the ZX80, such as a much better manual, display and string
String (computer science)
In formal languages, which are used in mathematical logic and theoretical computer science, a string is a finite sequence of symbols that are chosen from a set or alphabet....
handling, and called the ZX81 "a very good first computer" that "will open the world of computing to many who would be denied access to it by cost." However, the built-in memory was so small that use of a memory expansion pack was "mandatory for any worthwhile use". He also found the ZX81 to be alarmingly unreliable, having to have his first two test machines replaced before getting one that worked properly.
New Scientist's Malcolm Peltu commented that it was "great technical value for money particularly for computing enthusiasts" but thought that others were "likely to be bored very quickly by the basic system". He highlighted weaknesses in the manual and Sinclair's accompanying software, criticising them for "a misconceived design and sloppiness in execution which make the machine seem harder to use and more limited than it should" and questioned whether it might be more worthwhile to save up for a more powerful computer such as Acorn or Commodore's offerings. Overall, he concluded, the ZX81 might have a limited value in helping to teach BASIC programming and overcoming psychological barriers to computing, but "the Sinclair systems have a long way to go before they raise the quality and level of understanding of the nature and use of computer-based information systems among compute unbelievers."
While Personal Computer World editor Derek Cohen was on holiday in May 1981, his colleagues publicised the magazine's review of the ZX81 with a cover showing a chimpanzee with the machine above the strapline "Editor benchtests the ZX81". (The chimp returned in later issues to "benchtest" all of Sinclair's subsequent computers.) The review, which was actually written by PCW staffer Dave Tebbutt, acknowledged that the machine had significant shortcomings but nonetheless represented "absolutely amazing value for money". He described the ZX81 as "a lovely product which will have enormous appeal to people wanting to find out more about computers, but without it costing them an arm and a leg" and concluded: "If you know nothing about computers and you want to enjoy finding out about them, then this machine offers a value for money way of doing just that. Children will love the ZX81, there can be no question about that, and I suspect that more than a few people who are already familiar with computers will buy one, just to have a bit of fun."
Paul Taylor of the Financial Times
Financial Times
The Financial Times is an international business newspaper. It is a morning daily newspaper published in London and printed in 24 cities around the world. Its primary rival is the Wall Street Journal, published in New York City....
found the ZX81 to be "a powerful and flexible little computer ideally suited as a fun introduction to the mysteries of home computing" but cautioned readers about its limitations. It lacked ready-made software, the keyboard was not easy to use, it did not have sufficiently advanced graphics to be able to replicate arcade-style games and its built-in memory was inadequate. Even so, he suggested, "the ZX81 is a unique British product, part toy, part puzzle, part learning tool and I think that, provided one accepts its limitations and recognises that any computer will only do what it is told to do, it is good value as an introduction to the hobby of home computing."
David Babsky described the ZX81 as "a wonderfully brainy little micro which won't let you waste your time and make a fool of yourself". In a comparison between the ZX81 and IBM PC published in Which Micro?, he commended the ZX81's user-friendliness and its on-the-fly syntax checking of BASIC programs, which he described as "the feature that I, as a newcomer to computing, want to see incorporated into every micro."
Peripherals and software
The success of the ZX81 led almost immediately to enthusiasts producing a huge variety of peripherals and software. Clive Sinclair was "amused and gratified" by the attention the machine received but made little effort to exploit the demand, effectively ceding a very lucrative market to third party suppliers – a decision that undoubtedly forfeited a lot of potential earnings. W.H. Smith, for instance, was able to exploit a peculiarity of the ZX81; owners found that technically obsolete low-fidelity mono tape cassette recorders actually worked better as storage devices than higher-quality music systems. Smith's cashed in by buying up stocks of cheap "shoebox" cassette recorders in the Far East, sticking the W.H. Smith logo on them and selling them with a generous mark-up as "data recorders". Over 100,000 were sold in eighteen months.Sinclair released only two official peripherals for the ZX81 – a 16 kB RAM pack (actually the same one previously released for the ZX80, but rebadged) and the ZX Printer
ZX Printer
The Sinclair ZX Printer is a spark printer which was produced by Sinclair Research for its ZX81 home computer. It was launched in 1981, with a recommended retail price of £49.95....
, both of which plugged into the edge connector at the rear of the ZX81. They retailed at a launch price of £49.95 each but both had notable flaws. The RAM pack was top-heavy and was supported only by the edge connector. It had a habit falling out of its socket at crucial points and crashing the ZX81, losing anything that the user had typed in. Users turned to using sticky lumps of chewing gum, double-sided tape or Blu-Tack
Blu-Tack
Blu-Tack is a versatile, reusable putty-like pressure-sensitive adhesive produced by Bostik, commonly used to attach papers to walls or other surfaces....
to cure what became known as the "RAM pack wobble" problem. The ZX Printer was a tiny spark printer
Spark printer
A spark printer is an obsolete form of computer printer which uses a special paper coated with a layer of aluminium over a black backing, which is printed on by using a pulsing current onto the paper via two styli that move across on a moving belt at high speed. They were introduced in the late 1960s...
that used two electrically charged styli to burn away the surface of aluminium-coated paper to reveal the black underlay. It worked reasonably well at first but its output deteriorated rapidly after a time.
Many peripherals aimed to remedy the ZX81's flaws and provide many new capabilities that Sinclair had not tackled. These included proper typewriter-style keyboards, wobble-free RAM packs providing up to 64 kB of extra memory, more advanced printers and sound generators – and even a hard disk interface, which Clive Sinclair thought was "quite overgilding the lily". A wide range of software was also published. Within only a year of the ZX81's launch, around 200 independent companies had been established to manufacture and sell Sinclair-compatible hardware. The people behind the ZX81 cottage industry were very often not computer professionals but were, as the Financial Times noted, "school teachers, civil servants, electrical engineers and technicians [who] have set up small operations in their own time."
A dramatic illustration of the ZX81's explosive popularity came in January 1982, when civil servant Mike Johnstone organised a "ZX Microfair" at Westminster Central Hall
Westminster Central Hall
The Westminster Central Hall or Methodist Central Hall is a Methodist church in the City of Westminster. It occupies the corner of Tothill Street and Storeys Gate just off Victoria Street in London, near the junction with The Sanctuary next to the Queen Elizabeth II Conference Centre and facing...
. Seventy exhibitors set up their stalls with only a few hundred visitors expected in a hall with a capacity of 650 people. In the event, more than 12,000 people turned up and the police had to be called to control the crowd. Thousands of people, many of whom had travelled long distances to get there, queued outside for up to three hours to get into the hall. The exhibitors found themselves selling thousands of pounds' worth of software and hardware, "as fast as three pairs of hands on each stall could hand them over and stuff the fivers into improvised overflowing cash boxes."
Thousands of ZX81 programs were published, either as printed listings that could be typed in or as ready-made applications that could be loaded from cassette tape. Many computer magazines featured ZX81 program listings – some, such as Sinclair Programs, were dedicated entirely to listings – while many individuals became the archetypal "bedroom programmers", producing games and applications which they produced, marketed, recorded and sold from their own homes. Some went on to found their own software houses, employing teams of programmers – some of whom were still at school – to produce programs for the ZX81 and other computers. Existing companies jumped on the bandwagon as well, to profitable effect; 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. Psion's success with the ZX81 had a profound effect on the future of the company. Its work on the ZX81 database program Vu-File led to Psion switching its focus to the development of personal digital assistant
Personal digital assistant
A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...
s, which resulted in the launch in 1984 of the Psion Organiser
Psion Organiser
The Psion Organiser was the brand name of a range of pocket computer developed by the British company Psion in the 1980s. The Organiser I and Organiser II had a characteristic hard plastic sliding cover protecting a 6x6 keyboard with letters arranged alphabetically.Early Psions are very robust...
, the world's first handheld personal computer. Some of the most popular ZX81 games (Psion's Flight Simulation being an example) were rewritten for the Spectrum to take advantage of the newer machine's colour and sound capabilities.
Enterprising programmers were able to produce games for the ZX81 using nothing more than text characters and the machine's limited number of inverse video graphical blocks. Some ZX81 games achieved lasting fame, such as 3D Monster Maze
3D Monster Maze
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. The game was initially released by J. K. Greye Software in early 1982 and re-released later the same year by...
, a tense first-person perspective game that involved the player escaping a labyrinth with a Tyrannosaurus rex in pursuit. Written in a combination of BASIC and machine code
Machine code
Machine code or machine language is a system of impartible instructions executed directly by a computer's central processing unit. Each instruction performs a very specific task, typically either an operation on a unit of data Machine code or machine language is a system of impartible instructions...
, its innovative design led it to be hailed as the first home computer 3D game and a landmark in the history of computer and video games
History of computer and video games
The history of video games goes as far back as the 1940s, when in 1947 Thomas T. Goldsmith, Jr. and Estle Ray Mann filed a United States patent request for an invention they described as a "cathode ray tube amusement device." Video gaming would not reach mainstream popularity until the 1970s and...
.
One of the more bizarre software products for the ZX81 came about as a result of music companies attempting to capitalise on the popularity of Sinclair's computers. In 1983, EMI
EMI
The EMI Group, also known as EMI Music or simply EMI, is a multinational music company headquartered in London, United Kingdom. It is the fourth-largest business group and family of record labels in the recording industry and one of the "big four" record companies. EMI Group also has a major...
released a single by Chris Sievey that had a ZX81 program recorded on the B-side. Island Records
Island Records
Island Records is a record label that was founded by Chris Blackwell in Jamaica. It was based in the United Kingdom for many years and is now owned by Universal Music Group...
responded with XL1
XL1
XL1 was Buzzcocks frontman Pete Shelley's second solo album. The single "Telephone Operator" charted at #66 in the United Kingdom, making it his biggest single release there...
by Buzzcocks
Buzzcocks
Buzzcocks are an English punk rock band formed in Bolton in 1976, led by singer–songwriter–guitarist Pete Shelley.They are regarded as an important influence on the Manchester music scene, the independent record label movement, punk rock, power pop, pop punk and indie rock. They achieved commercial...
frontman Pete Shelley
Pete Shelley
Pete Shelley is an English singer, songwriter and guitarist, best known as the leader of Buzzcocks.-Biography:...
, packaged with a program for the ZX Spectrum.
Clones and variants
Timex Sinclair 1000
The Timex Sinclair 1000 was the first computer produced by Timex Sinclair, a joint-venture between Timex Corporation and Sinclair Research. It was launched in July 1982....
, Timex Sinclair 1500 (both variants of the ZX81) and the Timex Sinclair 2068
Timex Sinclair 2068
The Timex Sinclair 2068 , released in November 1983, was Timex Sinclair's fourth and last home computer for the United States market...
(a variant of the ZX Spectrum). The TS1000 was launched in July 1982 and sparked a massive surge of interest; at one point, the Timex phoneline was receiving over 5,000 calls an hour, 50,000 a week, enquiring about the machine or about microcomputers in general. It was virtually identical to the ZX81 save for rebranding and the addition of an extra 1 kB of memory, making for a grand total of 2 kB. In the five months following the TS1000's launch, the company sold 550,000 machines, earning Sinclair over $1.2 million in royalties.
Timex produced a second version of the ZX81 in the form of the TS1500, essentially an Americanised ZX81 launched in August 1983. It dispensed with the membrane keyboard and used a case similar to that of the ZX Spectrum, incorporating 16 kB of on-board memory. It was effectively a stopgap between the ZX81 and Spectrum. However, it was unsuccessful due to increased competition from rival US machines and the after-effects of Timex's botched marketing of the TS1000. Although the TS1000 had initially been a great success, Timex failed to provide the essential RAM pack upgrades to the market for two or three months after it launched the TS1000. Consumers would take the machine home, plug it in and find that it would not do anything useful due to the lack of memory.
In addition, consumers' attitude in the US was quite different to that in the UK. Clive Sinclair told Informatics magazine in June 1981 that "our competitors thought that consumers didn't want to learn programming. We [Sinclair Research] think they failed because of this and because of price." Timex evidently shared this belief but events proved it to be a false assumption. The TS1000/ZX81's price advantage was erased when its main rivals – the Texas Instruments
Texas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
TI99/4A
Texas Instruments TI-99/4A
The Texas Instruments TI-99/4A was an early home computer, released in June 1981, originally at a price of USD $525. It was an enhanced version of the less-successful—and quite rare—TI-99/4 model, which was released in late 1979 at a price of $1,150...
and the Commodore VIC 20 – had their prices cut to below the all-important $100 mark. Competitors such as Apple, Atari, Commodore and Texas Instruments promoted their machines as being for business or entertainment rather than education, highlighting the value of computers with ready-made applications and more advanced features such as graphics, colour and sound.
Consumers deserted the TS1000 once its novelty value had worn off and, as publishers of programming guides found to their cost, the American public showed little interest in using the machine to learn about computer programming. American retailers were left with large stocks of unsold machines. Burned by this experience, many were unwilling to stock the later Timex Sinclair machines in large numbers and the big chain stores dropped the Timex Sinclair line altogether.
Some companies outside the US and UK produced their own "pirate" versions of the ZX81 and Timex Sinclair computers, aided by weak intellectual property laws in their countries of origin. Several Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
ian companies produced ZX81 clones, notably the TK series (such as the TK 85
TK 85
The TK 85 was a ZX81 clone made by Microdigital Eletronica, a computer company located in Brazil. It came with 16 or 48 kB RAM, and had a ZX Spectrum-style case, more precisely a Timex Sinclair 1500 clone....
) from Microdigital Eletronica
Microdigital Eletronica
Microdigital Eletrônica Ltda. was an influential Brazilian computer company in the 1980s, based in São Paulo.- History :Established in 1981 by the brothers George and Tomas Kovari , its first product was the TK80, a clone of the British microcomputer Sinclair ZX80.The company...
of Brazil) and Prológica's CP-200. Czerweny Eletronica of Argentina produced the CZ1000 and CZ1500, clones of the ZX81 and TS1500 respectively. Lambda Electronics of Hong Kong produced the Lambda 3000, based on the ZX81, which was itself widely copied by other Chinese manufacturers.
The machines were not all straight copies of the ZX81; some, such as the CP-200, came with extra memory and a larger case (often with a chiclet keyboard
Chiclet keyboard
A chiclet keyboard or island-style keyboard is a computer keyboard built with an array of small, flat rectangular or lozenge-shaped rubber or plastic keys that look like erasers or "Chiclets", a brand of chewing gum manufactured in the shape of small squares with rounded corners...
in place of the original membrane keyboard). One clone, the TL801 from TELLAB of Italy, could emulate either the ZX80 or ZX81 and switch between the two machines via a jumper.
Impact and legacy
The ZX81 had an immediate impact on the fortunes of Sinclair Research and Clive Sinclair himself. The company's profitability rose enormously, from a pretax profit of £818,000 on a turnover of £4.6 million in 1980–81 to £8.55 million on a turnover of £27.17 million in 1981–82. Clive Sinclair became one of the UK's highest-profile businessmen and a millionaire, receiving a £1 million bonus on top of a salary of £13,000. He received a knighthood in the Queen's Birthday HonoursQueen's Birthday Honours
The Queen's Birthday Honours is a part of the British honours system, being a civic occasion on the celebration of the Queen's Official Birthday in which new members of most Commonwealth Realms honours are named. The awards are presented by the reigning monarch or head of state, currently Queen...
and the Young Businessman of the Year award in 1983.
The machine also had a widespread and lasting social impact in the United Kingdom. According to Clive Sinclair, purchasers of the ZX81 came from "a reasonably broad spectrum" that ranged from readers of the upmarket Observer and Sunday Times newspapers to the more downmarket but numerous Sun readers. The largest age group was around 30 years old. The Financial Times reported in March 1982 that most Sinclair computers were being bought for educational purposes, both for adults and children, though the children were usually able to learn much more quickly. Ian Adamson and Richard Kennedy note that the popularity of the ZX81 was "subtly different from the run-of-the-mill social fad"; although most enthusiasts were in their teens or early twenties, many were older users – often parents who had become fascinated by the ZX81s that they had bought for their children. On the downside, the ZX81 boom was overwhelmingly male-dominated.
One of the ZX81's key legacies was that it spurred huge numbers of people to try programming for the first time. This gave the UK a computing culture that was perhaps unequalled anywhere else and gave rise to a generation of expert programmers. The ZX81 plays a significant part in the plot of William Gibson
William Gibson
William Gibson is an American-Canadian science fiction author.William Gibson may also refer to:-Association football:*Will Gibson , Scottish footballer...
's 2003 novel Pattern Recognition
Pattern Recognition (novel)
Pattern Recognition is a novel by science fiction writer William Gibson published in 2003. Set in August and September 2002, the story follows Cayce Pollard, a 32-year-old marketing consultant who has a psychological sensitivity to corporate symbols...
. One character, an artist using old ZX81s as a sculptural medium, explains the cultural and intellectual impact that the machine had on British society:
Among those whose first experience of home computing was provided by the ZX81 are Terry Pratchett
Terry Pratchett
Sir Terence David John "Terry" Pratchett, OBE is an English novelist, known for his frequently comical work in the fantasy genre. He is best known for his popular and long-running Discworld series of comic fantasy novels...
(who used it for "very primitive word processing"), Edward de Bono
Edward de Bono
Edward de Bono is a physician, author, inventor, and consultant. He originated the term lateral thinking, wrote a best selling book Six Thinking Hats and is a proponent of the deliberate teaching of thinking as a subject in schools.- Biography :Edward Charles Francis Publius de Bono was born to...
and – perhaps proving William Gibson's point – many video game developer
Video game developer
A video game developer is a software developer that creates video games. A developer may specialize in a certain video game console, such as Nintendo's Wii, Microsoft's Xbox 360, Sony's PlayStation 3, or may develop for a variety of systems, including personal computers.Most developers also...
s including Charles Cecil
Charles Cecil
Charles Cecil MBE has worked in the interactive entertainment industry for 25 years. He is currently operating as Managing Director for UK based company Revolution Software which has released such critical and commercial hits as Beneath a Steel Sky and the Broken Sword series...
, Raffaele Cecco
Raffaele Cecco
Raffaele Cecco, born 10 May 1967, is a British video games developer who has created numerous video games since 1984, including Cybernoid and Exolon. He grew up in Tottenham in North London....
, Pete Cooke
Pete Cooke
Pete Cooke is a famous British computer games programmer, best known for his work published in the 1980s for the 8-bit home computers, especially the ZX Spectrum....
, David Perry (whose first published game, a driving game, involved "a black blob avoiding other black blobs"), Rhianna Pratchett
Rhianna Pratchett
Rhianna Pratchett is a freelance computer games scriptwriter, narrative designer and former journalist...
, and Jon Ritman
Jon Ritman
Jon Ritman is a software developer, notable for his work on major 1980s video games. Working primarily on games for the ZX Spectrum and Amstrad CPC home computer range. His first experience with a computer was at the age of 13, and first computer was a Sinclair ZX81 that he bought in 1981.His first...
.
Even though 2011 has seen the 30th anniversary of the ZX81, its legacy continues with active user forums in German and in English.
New hardware and software continues to be developed for the ZX81, including:
- a ZX81-based webserver;
- the ZXpand, a combined SD card interface, 32K configurable memory expansion, and optional joystick port and AY sound interface; and
- new games such as a port of the classic game, Nanako in Classic Japanese Monster Castle by the Mojon Twins and Virus by Bob Smith.
Other sources
- "From Science of Cambridge: the new MK14" (advertisement). Cambridge, England: Science of Cambridge (1978)
- ZX81 Operating Supplement. Cambridge, England: Sinclair Research (1982)
- Sinclair ZX81 Personal Computer (brochure). Cambridge, England: Sinclair Research (undated, circa March 1981)
- Sinclair Research advertisement. Everyday Electronics, April 1981, pp. 284–285
- Sinclair Research advertisement. Popular Science, October 1982, pp. 284–285
- Sinclair ZX81 Home Computer, with "Mapsoft" keyboard attached." McManus Galleries, Dundee. Accessed 13-1-2011
- TK85. Museu da Computação e Informática. Accessed 2-1-2011
- ZX81DES1. Rick Dickinson, 24 August 2007. Accessed 2-1-2011.
- Sinclair ZX81. Sinclair Research. Accessed 5-1-2011.
External links
- Sinclair ZX80/ZX81 Discussion Forums
- ZX81 Download Page
- ZX81 Online Museum
- ZX81 Java emulator
- Sinclair ZX81 Teardown - a detailed look at the ZX81's hardware