Sinclair ZX81
March 5, 1981 for £ 69.95 November 1981 for US $ 149.95 Fall 1981 for DM 398 December 1981 for ¥ 38,700
64 × 48 pixels (block graphics, black and white)
The Sinclair ZX81 is a home computer based on the Z80 microprocessor from the British manufacturer Sinclair Research Ltd. The number in the name refers to the year of the market entry on March 5, 1981.
The ZX81 is a further development of the ZX80 and was designed from the start as a mass product for beginners. Originally only available as a mail order item, the ZX81, which was massively advertised as an inexpensive learning computer, also conquered shops in Great Britain from the end of 1981. In addition, sales also started in continental Europe, North America and Japan. Within a very short time, large quantities - including the accessories that Sinclair has meanwhile launched on the market - were sold worldwide. Due to the poor workmanship and faulty system software of the first production series, almost every fourth device was initially complained about, but this did not affect the continued enormous demand.
In the course of its great success, both legal and unauthorized replicas were made. The Timex Sinclair 1000 ( TS1000 for short ), produced by Timex Corporation under license for the North American market, was able to conquer further large market shares, particularly in the USA. The Timex Sinclair 1500 ( TS1500 for short ), which was released later, was not a success. Most of the unlicensed products appeared in South America and Asia. Including all replicas, a total of around two million devices had been sold worldwide by the end of production in 1984. After the ZX80, the ZX81 finally paved the way for the age of the computer as a mass product.
history
The first was led by Clive Sinclair and his company Science of Cambridge for the English market developed computer frameless single-board MK 14 with LEDs - seven-segment display , was offered from June 1978 in the UK as transit goods. With an estimated 15,000 units, the high sales figures achieved within a short period of time enabled further development activities. This ultimately resulted in the manufacture of an inexpensive compact device called the ZX80 . The computer, which was designed exclusively to minimize costs in terms of materials and production, was nevertheless profitable and was offered for sale in Great Britain from January 1980 for £ 99.95 as the first device below the psychologically relevant mark of £ 100 in Great Britain. With around 100,000 copies sold within 18 months, the ZX80 quickly became a box office hit. Even before its market entry, a successor model, the ZX81, was already being worked on from September 1979.
Development and prototypes
The device to be developed should be even more powerful than the ZX80 at a lower selling price. For this purpose, the successful system architecture of the ZX80 was adopted and investments were made in the latest technology to further reduce material and manufacturing costs.
Cost minimization through special ULA module
Of the cost-intensive components built into the ZX80, the functions of a total of 18 integrated circuits could be simulated on a single special component with the help of the still young ULA technology by Ferranti Limited . The associated development and production costs were quickly put into perspective with the quantities targeted by Sinclair and, in total, led to the desired cost reduction. The advanced computer, equipped with a maximum of five electronic circuits, could then be offered profitably at a price of just under £ 70. In addition, the utilization of further available capacities of the special module made it possible to eliminate technical problems of the ZX80. A newly implemented operating mode enabled the annoying screen flickering to be eliminated.
Improvement of the Sinclair BASIC
In addition to reducing the number of components, the aim was to improve usability and increase the performance of the easy-to-learn Sinclair BASIC programming language, which is also included in the ZX80 . The responsible Nine Tiles Networks Ltd. then integrated floating point routines , expanded the range of commands and error handling of the BASIC interpreter , improved the editing options and fixed numerous known problems in the system software of the ZX80. The self-imposed claim to join the ranks of full-fledged computer manufacturers with the ZX81 was to be demonstratively taken into account in November 1980 by renaming the company to Sinclair Computers .
WH Smith and BBC
During the development phase of the ZX81, Sinclair Computers explored further marketing options in order to be able to discard the image of the pure mail order company. The British book chain W. H. Smith & Son should benefit from this. To stimulate its stagnant business, it had recently launched a program to introduce the population to computer technology. The associated new knowledge department “Computer Know-How” was supposed to have a more convincing effect and attract more interested parties thanks to a computer that could be purchased directly on site. The ZX80 fits perfectly into this concept due to its ease of use and its low price. The high sales figures already achieved and thus the great popularity of the computer also promised profitable margins for W. H. Smith & Son. Corresponding sales inquiries for the ZX80 to Sinclair followed. Sinclair then informed W. H. Smith & Son of the new development and recommended that this ZX81 be marketed instead . Those responsible at W. H. Smith & Son agreed, but on the condition that they were able to convince themselves of the promised qualities on a prototype beforehand .
When it became known that the British broadcaster British Broadcasting Corporation (BBC) was looking for a suitable device for later distribution for its planned new series of programs on home computers, Sinclair Computers developed brisk marketing efforts in this environment too. At the end of 1980, a first demonstrable prototype - still without a housing - was quickly manufactured for presentation at the BBC in December 1980. However, the BBC did not follow Sinclair's philosophy of a mass product designed exclusively for a low purchase price. Instead, the BBC relied on fully-fledged technology, reliability, user-friendliness and easy expandability. The bid went to rival Acorn , which introduced its higher quality BBC Micro in January 1982.
Sinclair printer
During the negotiations with the BBC, Nine Tiles Networks Ltd. worked on the expansion of the system software to control an electric erosion printer , which is also to be developed . Due to the late decision by Sinclair in favor of the printer and the resulting time pressure, numerous errors crept into the extensive system software of the ZX81. At the end of 1980, the first work followed to bring the computer prototypes into series production and on the documentation to be delivered. After completing the revisions of hardware and software and the resulting fixed dimensions of the interior, the Sinclair engineers replaced the ZX80's housing, which was prone to damage, in the last development phase. The new desk-shaped chassis manufactured using injection molding technology was smaller, more robust and better suited to contemporary tastes. A prototype with this new case was then presented to those responsible at W. H. Smith & Son in January 1981. Impressed by the technical and economic data, a deal was quickly reached with Sinclair Computers. Part of the contract was an exclusive right to sell the ZX81 for retail outlets by W. H. Smith & Son. Both contracting parties saw their near future secured. Sinclair then intensified its research activities, including the successor model ZX82 - the later Sinclair ZX Spectrum - and in March 1981 changed its name to Sinclair Research .
As with large parts of the ZX80, the production of the ZX81 was also carried out by the troubled Scottish branch of the US watch manufacturer Timex Corporation in Dundee .
marketing
The official sales of the ZX81 took place in Great Britain on March 5, 1981, initially - as with all previous Sinclair devices - exclusively as dispatch goods. The market entry was accompanied by aggressive and ubiquitous advertising campaigns, which were largely tailored to the person of Clive Sinclair and tried to put him in the right light as the ingenious savior of computer technology. Large-format advertisements appearing almost daily in well-known newspapers and magazines praised Sinclair's products as a prayer wheel as an essential and indispensable part of the new computer age. Technology enthusiasts and the future generation, children and adolescents, were promised a quick and easy entry into the promising world of computers at an “incomparably low price” of £ 69.95. An argument that, in view of the sometimes many times more expensive competing products Acorn Atom (kit from around £ 120), Apple II (from around £ 549), Atari 400 (from around £ 295), Commodore VIC-20 (from around £ 160) and the TRS-80 (Model III from around £ 559) has had an impact on many hobbyists and parents concerned about the future of their children.
Delivery difficulties
The unexpectedly high demand sparked by massive advertising soon led to delivery bottlenecks - customers had to wait up to nine weeks for their devices. In addition, there were a large number of complaints due to faulty devices, the cost-minimized components of which often did not withstand the continuous stress in everyday life. In particular, the voltage stabilization built into the devices and the external power pack proved to be undersized and very error-prone. In addition, there were problems with the system software, which allowed the computer to be operated in general, but made more ambitious projects unnecessarily complicated due to faulty floating point routines. These problems in connection with a completely overwhelmed customer service did not affect the unrestrained demand, on the contrary - an end to the sales growth was not in sight.
Development of the education sector
Meanwhile, Sinclair Computers turned to the prestigious supply of educational institutions. An existing government program to promote computer use in schools only subsidized competing models, including those from Acorn, to Sinclair's displeasure. Sinclair initiated its own sales program for schools with a general discount on all devices in the ZX81 series, with the BBC barely wounded, but also with the large-scale advertising effect and image enhancement in mind. A complete package consisting of the ZX81 and memory expansion (later also including a printer) was then offered for £ 60 (or £ 90) - 40 percent cheaper than the cheapest subsidized computer in the government program. As a result, 2,300 schools took up the offer and from mid-1981 the ZX81 became the most widely used computer in British schools, according to Sinclair.
Exclusive sale by the bookstore chain WH Smith
In the meantime, through optimizations carried out in the production facility, Timex Corporation had significantly streamlined the manufacturing processes. This shortened the long waiting times from initially more than two months to the three weeks promised in the advertisements. With the devices that were now sufficiently producible, W. H. Smith & Son also received the promised contingents for its branches from September 1981. Thanks to the generous profit margin of 40 percent of the sales price and other additional income associated with the ZX81, the book chain was able to generate the significant profits it had hoped for in the course of the first year of sales. In addition, the sales of 350,000 computers achieved by W. H. Smith & Son in the same period finally established the ZX81 as the dominant factor in the British home computer market, a development entirely in line with Sinclair Research.
International sales
In addition to supplying W. H. Smith & Son, the meanwhile expanded production capacities also allowed the successful device to be exported. From October, in cooperation with American Express, the first test sales were made in the USA, which was then the largest computer market in the world. After the successful test phase, regular mail order sales of the ZX81 began in November 1981. With an unrivaled low price of $ 149.95 for the finished unit and $ 99.95 for the kit, sales soared within weeks with around 15,000 units sold monthly. The USA thus developed into the main sales market in the course of the first half of 1982. With the success in the back, further sales service providers could also be won for continental Europe and Japan (Mitsui exclusive sales). In West Germany, the ZX81 went on sale at the end of 1981 for 398 DM, initially exclusively as a shipping item, a little later in Sinclair Germany's own shop in Munich. After the ZX81 quickly gained greater popularity in West Germany due to its permanent presence at trade fairs and exhibitions, from mid-1982 onwards sales were expanded to include partners such as the well-known electronics provider Vobis .
Distribution in the countries of the Eastern Bloc was prohibited due to the CoCom embargo. This also fell victim to initially good duty-free sales of the ZX81 at larger British airports. After the exclusive period for W. H. Smith & Son expired, other well-known British department store chains such as Boots , John Menzies and Currys were included in the distribution. By July 1983, around 1.5 million computers had been sold worldwide. This great success has meanwhile also called numerous imitators - with or without a license - on the scene.
Authorized replicas: Timex Sinclair 1000 and 1500
TS1000
TS1500
Despite doing well in the US mail order business, Sinclair Research did not have the resources to open up the North American retail market. Timex Corporation, established in the USA and whose branch in Scotland manufactured the ZX81, offered itself as a cooperation partner for the in-store sales of the ZX81. The licensing model agreed between the two in January 1982 provided for a fee of five percent of the sales value for Sinclair Computers. In return, Timex was granted the right to sell the device, which they produced under license and which could be adapted to North American needs, under its own name. The device, which was then expanded by an additional 1 KB RAM and a shielding plate, was manufactured in one of the Timex plants near New York City and was henceforth offered under the name Timex Sinclair 1000 ( TS1000 for short ). The market launch in the approximately 70,000 interested US retail outlets began in July 1982. With a sales price of $ 99.95, 550,000 units were sold in the second half of 1982, significantly exceeding mail order sales of the ZX81 in the first half of the year. Sinclair Research's share of the profits was approximately $ 1.2 million.
In order to counteract the slump in sales that began in 1983, the Timex Sinclair 1500 ( TS1500 for short ) - essentially a ZX81 with 16 KB RAM and an improved keyboard in a larger housing - was quickly brought to series production. When it entered the market in August 1983, US competitors were already offering significantly more powerful devices in the form of the Commodore VIC 20 and the TI-99 / 4A, also at very affordable prices. In this environment, the technically outdated TS1500, marketed as a learning computer, did not succeed in attracting American customers, who are now more interested in entertainment and business computers. Sales fell far short of high expectations, and production was discontinued in February 1984.
Unauthorized replicas
CP200
TK85
In addition to the official replicas from Timex, there were a number of other devices that were technically and optically very similar to the ZX81. Often only minor changes were made or the system software replaced. In many cases, the ULA special component was simulated using standard chips. This is what happened to most of the clones made in South America, such as the TK82-C and TK85 from Microdigital Eletrônica Ltda, which were sold in large numbers in Brazil . In 1983, Sinclair Research initiated legal proceedings for copyright infringement by a Brazilian court, but in favor of Microdigital Eletrônica Ltda. decided, which saved the Brazilian manufacturer considerable back payments in license fees.
In some cases, devices based on the ZX81 have been expanded to include additional functionalities, with 100 percent downward compatibility with the original being achieved by replacing the system software on the read-only memory with that of Sinclair . The Lambda 8300 falls into this category with 16 KB RAM ex works, sound output, improved keyboard and an Atari-2600 -compatible joystick connection ( D-Sub : two-row 9-pin). In addition, the manufacturer Lambda Electronics Ltd. from Hong Kong offered various extensions such as color and memory upgrades. Clones of the Lambda 8300 itself were also made, which, for example, also found buyers in West Germany in the form of the Power 3000 .
Overview of the best-known replicas not authorized by Sinclair or Timex
| clone | original | Marketing area | Manufacturer |
|---|---|---|---|
| CZ1000 | TS1000 | Argentina | Czerweny Electronica (Argentina) |
| CZ1500 | TS1500 | ||
| CP200 | ZX81 | Brazil | Prológica (Brazil) |
| NE-Z8000 | Nova Eletrônica (Brazil) | ||
| Ringo R470 | Ritas do Brasil (Brazil) | ||
| TK82-C | Microdigital Eletrônica Ltda. (Brazil) | ||
| TK83 | |||
| TK85 | TS1500 | ||
| Polybrain P-118 | ZX81 + accessories | New Zealand | David Wells Ltd. (New Zealand) |
| Lambda 8300 | Great Britain | Lambda Electronics Ltd. (Hong Kong) | |
| Power 3000 | Lambda 8300 | West Germany | Creon Enterprises (Hong Kong) |
| Basic 3000 | Scandinavia | unknown | |
| DEF 3000 | France |
Modern replicas
The simple and manageable architecture of the system enables the miniaturized replica of the ZX81 with today's technical means with at the same time manageable effort, although the underlying system software is still subject to copyright restrictions by its developer Nine Tiles Networks Ltd. subject. Such a modern realization took place for the first time in 1997 - as with other home computer systems - as an implementation on a programmable logic circuit ( FPGA ) together with an embedding system . The simulations using FPGA technology were only intended as technical feasibility studies due to the protected system software.
Technical details
The housing of the ZX81 contains a single board with the computing and memory modules, the peripheral connections, the external system bus for expansions, the screen output on a television and the voltage control for the external power supply unit. The main electronic components are the Z80 - CPU ( central processing unit ), the Sinclair Logic Chip in ULA technology and the working memory (RAM) and read-only memory ( ROM ). In addition to the computer, the scope of delivery included a power supply unit (9 volts , DC voltage ), the antenna cable , a cable for connecting to a cassette recorder (for holding a compact cassette that served as a magnetic storage medium ), and the ZX81 BASIC Programming operating instructions . It was later delivered together with the 16 KB memory expansion from Sinclair. There is no power switch, commissioning takes place by plugging the power pack into the socket. In the case of the kit, the assembly of the printed circuit board and the final assembly of all components must be carried out by the user.
Main processor
The system architecture of the ZX81 computers is based on the Z80 microprocessor from Zilog or a license version from NEC in the version clocked at 3.5 MHz . The Z80 CPU can access an address space of 65536 bytes , which also defines the theoretically possible upper limit of the main memory of 64 kilobytes (KB). For practical reasons, it is common for addresses instead of decimal notation , the hexadecimal to use. This is usually preceded by a $ symbol to make it easier to distinguish. The addresses from 0 to 65535 in decimal notation correspond to addresses $ 0000 to $ FFFF in the hexadecimal system.
Sinclair Logic Chip (ULA)
The special component manufactured in ULA technology , a forerunner of today's FPGA components, combines the functions and ZX81-specific additions that were implemented in the previous model ZX80 using separate integrated circuits. This includes large parts of the screen control, the system clock generation, the cassette interface, a rudimentary memory management and the circuit logic for the keyboard query. The ULA2C184E used in older ZX81 computers was later replaced by the revised model ULA2C210E . The improved image signal could thus be displayed correctly on all television sets available at the time. The outputs for the different TV standards SECAM , NTSC and PAL were different, depending on the market made fixed wirings realized ULA of the block on the board.
Storage and storage allocation
The address space that can be addressed by the main processor is segmented in the ZX81 into sections of different sizes. The 8 KB system software, which is stored on read-only memory, together with the BASIC interpreter is located in the lowest address range from $ 0000 to $ 1FFF. This is followed by a free block up to $ 3FFF, which can, however, be used by 64 KB memory expansions. The static main memory built into the ZX81 with a capacity of 1 KB is in the range from $ 4000 to $ 43FF , while the TS1000 with its 2 KB RAM ranges from $ 4000 to $ 47FF. If a plug-in RAM extension is used, this is also displayed at $ 4000 and, depending on the size, extends up to the address $ FFFF. However, the entire address space cannot be used because the system software displays the video data for reading by the CPU from $ C000. The main memory built into the computer is switched off when memory expansions are used. The system software stores 125 bytes of variables, the input buffer, the system stack, the BASIC programs to be entered by the user and the screen data (minimum 25 bytes, maximum 793 bytes) in RAM from address $ 4000.
graphic
The black and white screen output of the ZX81 is standard with black characters on a white background via a coaxial HF antenna connection . The system software coordinates the cooperation of the CPU with the ULA special chip, which takes on the actual image processing and outputs it via the TV modulator. The CPU only serves to transfer the image data stored in the main memory, since only the CPU can access the contents of the RAM.
The image generator contained in the ULA special chip enables the output of 256 pixels for 192 television lines. The system software and BASIC interpreter only support elements with a size of 8 × 8 and 4 × 4 pixels, sufficient for a text mode with 32 × 24 characters and block graphics with 64 × 48 pixels ( picture cell , graphic block ). In addition to alphanumeric characters , the ZX81 also provides graphic characters. However, this character set is not ASCII- compliant, which makes the exchange with graphic data from other computers and the control of printers much more difficult. In computer configurations with at least 16 KB RAM, the character set can be replaced by the user.
In the case of computer models with less than 4 KB of RAM, the lines on the screen are shortened and stored in the RAM by omitting all spaces on the right in a line. This data reduction , carried out automatically by the system software, enables more efficient use of the working memory. With the appropriate control characters , only 25 bytes of data are required for a completely empty screen. A filled screen without spaces, on the other hand, results in 793 bytes of screen data, which means that there is not much space left for the user's program on devices with 1024 bytes of RAM. In addition to occupying the already scarce memory, the CPU is also heavily used by the image generation, so that, depending on the display mode, up to 75 percent of the computing power is used for this. In slow mode , interrupt- controlled image generation has the highest priority. User programs are only executed when the image display has already been completed. This mode leads to a flicker-free image, but only 25 percent of the CPU processing power is left for the tasks of the user. In Fast Mode , on the other hand, the program to be executed is first processed and the image display - which is no longer flicker-free - is started or continued after a special release. The user can choose between these two modes depending on the task at hand. Data transfer via the cassette interface is an exception. In this case, the system software automatically switches to Fast Mode to ensure a stable data transfer rate.
The unsupported by the system software high-resolution graphics modes with 192 × 256 pixels require appropriate driver programs from other manufacturers, and in addition about 6 KB of memory, thus essential for the operation of a memory expansion is (with the exception of WRX Hi-Res - driver ). The two operating modes True Hi-Res and Pseudo Hi-Res are based on graphic characters. Only with True Hi-Res are the positions of the pixels freely selectable. The Pseudo Hi-Res , which is restricted in the positioning of the pixels, works without hardware modifications to the memory expansion.
Interfaces
Due to the lack of a PIO module, the ZX81 has no serial or parallel interfaces . Only the external system bus can be used as a 46-pin expansion slot. Jack sockets are used to connect a standard cassette recorder and as a power supply input.
Periphery
Mass storage
In connection with mainly western home computers from the 1980s, cassette recorders and floppy disk drives were mainly used for data backup , while hard and removable disk drives were increasingly used in the professional environment for personal computers . The cheapest variant of data recording using compact cassettes generally has the disadvantage of low data transfer rates and thus long loading times, whereas the much faster and more reliable floppy and disk drives were much more expensive to purchase. When the ZX81 was released, only cassette recorders were available for mass storage.
Cassette systems
The ZX81 has a factory-fitted cassette interface (mono jack socket) for recording and reading out data using standard cassette recorders. Corresponding compact cassettes serve as storage media . The standard data transfer rate is an average of 300 bit / s. To ensure more reliable recording and thus also to interchangeability of cassettes from different devices, the use of either mono devices or controllable stereo devices with a correctly set magnetic head is recommended. Various accessories have been offered by third-party manufacturers to increase the data transfer rate. For example, with QSAVE - a hardware band filter connected between the cassette socket of the computer and the data recorder - data can be transmitted at rates of up to 3000 bit / s.
The ZX-99 cassette interface from Data-Assette, which was already available shortly after the ZX81 entered the market, enables two to four cassette recorders to be controlled simultaneously. Direct and buffered copies between the individual cassette recorders are possible, with control via BASIC commands of the ZX81. Corresponding driver software is provided by the expansion in a 2 KB ROM. The transmission rate of 300 bit / s corresponds to that of the ZX81 system software. In addition, the extension contains an RS-232 interface with an integrated ASCII converter for text output on appropriate printers.
Floppy disk systems
As early as 1982, simple floppy disk systems for use with the ZX81 came onto the market from third-party manufacturers. The Macronics Disc System is a floppy disk interface based on the Shugart interface . It allows the use of corresponding 5¼ inch drives (SA-400) along with hard-sectored floppy disks. It is controlled via system software provided on a 2 KB EPROM with ten different commands. Thanks to the simple electronic control without a special floppy disk controller , the storage capacity per disk side is only 42.5 KB with 35 tracks and 48.75 KB with 40 tracks combined with an average data transfer rate of around 3000 bit / s. In addition, the extension has an RS232 interface for controlling the corresponding printers. The LarKen 1000 diskette system, with a storage capacity of around 46 KB per diskette, has roughly the same performance features as the Macronics Disk System, but includes more extensive and easier-to-use system software. Devices released later, such as those from the Metrimpex company, achieve storage capacities of up to 200 KB per data carrier.
printer
The accessories supplied by Sinclair for the ZX81 include an electric erosion printer to be connected to the expansion port. Its printouts with a maximum width of 32 characters, each with 8 × 8 printing points, are made on black roll paper metallized on one side. During printing, the paper tape is passed between a pair of opposing needle electrodes that are located on a movable carriage. At the position of a pressure point to be set, an electrical sparkover (arc) is then generated between the two electrodes. The light metallic coating is evaporated (eroded) at the point of breakdown and the undamaged paper behind it appears in the form of a black dot.
The printer can be controlled entirely using the ZX81 system software. Using the looped-through expansion port on the printer's connector, the device can be used to operate additional accessories such as memory expansions. Due to the inferior mechanics and quality fluctuations in the printing paper, the results achieved are of below average quality. Nevertheless, the typeface is legible and suitable for printing programs for archiving purposes as long as the paper is only exposed to low humidity. At the same time, word processing-compatible printers were many times more expensive, so that the printer, which Sinclair Computers initially offered for only £ 49.95 at the end of 1981, found widespread use by the end of production in early 1984 despite its very limited options. Manufactured by Timex Corporation in Dundee, Scotland.
A further development of the Sinclair printer is the Timex Sinclair 2040 , originally intended only for North American sales , which was later also sold in Europe as the Alphacom 32 for £ 60. By using white thermal paper and more sophisticated control technology, a better print image is achieved in an even shorter time than with the predecessor. In addition, the slow and loud Unihammer printer GP-50S from Seikosha , which uses normal paper, can also be used with the ZX81 without additional software.
Input devices
The flat membrane keyboard built into the ZX81 has 40 keys of the same size in a QWERTY arrangement. Unlike most computer keyboards, the space bar is located on the lower right edge. In addition to the common alphanumeric characters, 20 special graphic characters and BASIC command characters can be addressed using the Shift and Function keys.
The keyboard consists of three plastic sheets glued on top of each other. On the upper and lower foil under the buttons there are metallic contacts that are interconnected according to a given scheme. The middle, thick and elastic film serves as an electrical separating layer and return spring. At the position of the keys, it has holes, the dimensions of which are large enough to enable a current to flow between the upper and lower film when the key is pressed. Since the keys that work as closer are unergonomic and have no pressure point , it is almost impossible to work efficiently and for longer with the keyboard. Many users then retrofitted them with the help of add-on extensions or, in many cases, used an externally connected, fully-fledged keyboard from third-party manufacturers.
Extensions
Many extensions and conversion kits of various sizes have been published for the ZX81, although only the most important are listed below.
Memory upgrades
The very tight working memory of only 1 KB due to the price pressure is by far not sufficient for most programming projects. In addition to the user's program data, the RAM contains the screen data (minimum 25 bytes, maximum 793 bytes) and the system variables (125 bytes). When the screen is completely filled, only about 100 bytes are available, which makes memory upgrades unavoidable even for smaller applications. The 16 KB memory module, which Sinclair sold for £ 49.95 shortly after the ZX81 went on sale, is used via the expansion slot. However, due to the inadequate fit and contact problems caused by oxidation , even the smallest vibrations - as can occur with normal computer use - often result in complete failure and thus data loss. In addition, Sinclair's extension does not have a looped-through slot , so that it can not be connected in series and a maximum of 16 KB RAM can be upgraded. For this reason and because of lower prices, many users turned to memory expansions from third-party manufacturers.
A high-quality processed memory expansion was offered , for example, by the third-party manufacturer Memotech . Its expansions also have a looped-through expansion port, with which several 16 KB memory modules can be plugged in one after the other or combined with other Memotech expansions. However, the address space in which they are to be displayed must first be set by the user using the DIP switches on the respective module housing . In addition to the 16 KB extensions, Memotech also delivered versions with 32 KB and 64 KB RAM a little later.
Graphic modifications
In order to improve graphic capabilities, a large number of extensions were available from 1982, including for color display and the use of high-resolution graphics or combinations thereof. The Haven Hardware Color Board , which is to be operated at the expansion port and provided with its own color memory, went on sale in 1982. With the help of appropriate POKE-BASIC commands , the characters of the ZX81 can be output in 16 different colors. This standard character set can be expanded to 900 graphic symbols with the help of the 4K Graphics ROM Board offered by Kayde Electronic Systems from 1982 . The symbols it contained, along with a 16 KB memory expansion, were often essential for playing the arcade implementations Peckman ( Pac-Man ), Centipede and Space Invaders sold by Kayde . Various additives were available for displaying high-resolution graphics. The HRG interface from Memotech, for example, makes it possible to display high-resolution graphics with 192 × 248 pixels on the ZX81. The expansion, which was sold from 1982 onwards, contained the necessary driver software in a 2 KB EPROM with corresponding BASIC commands for setting points, drawing lines, etc. In addition, horizontal and vertical fine adjustment ( scrolling ) is possible.
Sound generating devices
The ZX81 was shipped from the factory without any sound generation facility. Since the availability of games and the associated sound effects also played a not inconsiderable role for ZX81 users, third-party manufacturers offered expansions of various sizes. Many of these add-ons use the special programmable components of the AY-3-891X family from General Instrument and common speech synthesis electronics . The ZXM Soundbox (AY-3-8912, built-in amplifier and loudspeaker) and the ZXS Speech Synthesizer from Timedata Ltd., the SON X-81 (AY-3-8912 , which is often advertised in magazines ) are among the best-known extensions for music and sound generation , built-in amplifier and loudspeaker) from Bi-Pak and - as one of the first offered - the QS Sound Board (AY-3-8910, external sound output) from Quicksilva .
Input and output supplements
The ZX81 does not have any electronic assemblies for controlling inputs and outputs, such as those required by joystick or standard peripheral connections. Corresponding expansions, for example to supplement RS232 or Centronics interfaces, can be retrofitted. The best known are I / F Centronics from Memotech, which was later also available with a Buffer Pak keyboard for Memotech's external keyboard. There are also other input-output ports available as a kit from Maplin, the ZX81 Input / Output Controller TE10 from Thurnall Electronics and, for example, a Competition Pro joystick converted by Kempston Micro Electronics for use with games.
software
As with other home computers of the 1980s, commercial software was distributed on various data carriers. The inexpensive compact cassettes, particularly popular with game manufacturers, were, however, very prone to errors due to the high mechanical stress on the magnetic tape, and their use was often associated with long loading times. In the case of the plug-in modules, which are much more expensive to manufacture, the programs contained therein were available immediately after switching on the computer, which was a great advantage in particular for system software and frequently used applications. The floppy disks achieved the best compromise between loading time, reliability and storage capacity. The floppy disk drives, which were still very expensive in 1982, were hardly supported for the ZX81.
In addition to the selection of commercial programs of all kinds sold by Sinclair Research, the range of programs for the ZX81 computers also included software ( listings ) developed in-house and published in magazines and books . Most of the commercial programs were offered on compact cassette, a few were available on cartridge.
Illegal copies ("pirated copies") always made up a large part of the software in circulation and often presented small software developers with existential economic difficulties. As a result, copy protection systems were increasingly used, especially in games, as the best-selling software.
System programs
The configuration of the ZX81 hardware, which also includes the control of the cassette interface, is the responsibility of the Sinclair OS operating system . It is one of Nine Tiles Networks Ltd. made further development of the operating system of the ZX80. In order to optimize the interaction with the Sinclair BASIC interpreter and the printer driver, which is also on the ZX81-ROM, all individual components are very closely interwoven in terms of programming.
Sinclair BASIC
In order to market the ZX81 as a learning computer suitable for the masses, special attention was paid to an easy-to-learn programming language integrated in the device. The Sinclair-BASIC already built into the ZX80, an incomplete adaptation of the ANSI Minimal BASIC, was then fundamentally revised and the read-only memory containing the BASIC was enlarged to 8 KB. The execution of the programming work was entrusted to Nine Tiles Networks Ltd. which made extensive extensions to both the interpreter and the editor for entering and correcting the program data. The fundamental innovations included simplified editing options and error evaluation after entering a program line. The latter represented a novelty for interpreter languages in the home computer sector, for which until then an error analysis was associated with greater effort even for experienced programmers. In addition, full floating point arithmetic and commands for operating the Sinclair printer have been integrated. The Sinclair-BASIC does not correspond to the then common de facto standard in the form of Microsoft BASIC - it is rather a dialect of its own . Sinclair BASIC programs created on the ZX81 cannot be run on other computers without additional modifications.
To increase the speed of execution of BASIC programs, compilers convert them into executable, i.e. H. machine code programs that can run without a BASIC interpreter can be converted. However, the range of supported BASIC commands and variables is limited. One of the best-known compilers is the M-Coder from PSS
Applications and games
In addition to the Sinclair BASIC, the ZX81 programming languages ZX Forth from Sinclair Research and the Z80 assembler from Memotech are available for the ZX81 .
By far the largest part of the both commercial and freely available ZX81 software are the games. These include primarily arcade versions, but also genre-defining originals such as 3D Monster Maze as the founder of three-dimensional maze games. A total of around 100 games from different manufacturers were released, including Manic Miner , Mazogs , Pimania and simple chess, text and shooting games.
Magazines
In the 1980s, along with specialist books, computer magazines played an important role for many home computer owners. The editions, which were often published monthly, contained test reports on innovations, programming instructions and software for typing. They also served as an advertising and information platform as well as for establishing contact with like-minded people.
A variety of kiosk and subscription publications tailored to their needs were available for ZX81 users. The best-known commercial computer magazines include Sinclair User , Sinclair Programs, and Sinclair Projects . The German-language magazine ZX User Club was published in West Germany especially for German interested parties .
emulation
After the end of the home computer era at the beginning of the 1990s and with the advent of powerful and affordable computing technology at the end of the 1990s, programs for emulating home computers and their peripherals were increasingly developed by committed enthusiasts . To play old classics from a wide variety of home computer systems, a single modern system with data images of the corresponding home computer programs is sufficient with the aid of the emulators. The emergence of emulators set in motion, among other things, an increased transfer of software that might otherwise have been lost to modern storage media, which makes an important contribution to the preservation of “digital culture”.
As a powerful emulator of the applicable web browser executable Java -based Timex / Sinclair 1000 emulator and for Linux available, and other systems ZEsarUX .
reception
Contemporary
When the ZX81 appeared, the assessments turned out differently. The reviews ranged from complete rejection as an “overpriced game console” to “the ZX 81 is fully usable as a teaching and learning aid” to euphoric dubbed “milestone when it comes to the integration of computer technology”.
The removal of the shortcomings of the predecessor model with compact dimensions and better workmanship was received positively. The extended BASIC with its beginner-friendly error handling and detailed documentation also knew how to please. The keyboard was almost unanimously criticized for being unsuitable for longer use and also not being ASCII-compliant. The slow execution speed of BASIC and its incompatibility with the de facto standard of Microsoft BASIC at the time were also criticized. Due to the minimal equipment and only limited expandability, the ZX81 was mainly characterized as an entry-level model. For such a low price you can't really go wrong with a purchase and, for example, offer children (“Children will love the ZX81”) a good opportunity to introduce them to the world of computers, according to the unanimous opinion of all reviewers.
Retrospective
Shortly after the end of production in the mid-1980s, the computer was described as “a classic among home computers” that was “absolutely cheap” and still performed “great”.
In the meantime, the ZX81 is being noticed more and more on websites, magazines and books and, in retrospect, it is classified as the first affordable home computer alongside the ZX80 (“Everyone can afford the ZX81”). Even “without color, sound and joystick” the “mini computer” and “improved ZX80 at a reduced price” were even “important as a play device.” The ZX81 opened the computer market to the masses and thus opened up completely new perspectives:
"While its successor, the Sinclair Spectrum, got the nation playing computer games, the ZX81 was the tipping point that turned the home computer from nerd hobby into something anyone could buy and use."
"While its successor, the Sinclair ZX Spectrum, brought the nation to play computer games, it was the ZX81 that ushered in the transition from home computers as a purely niche product to mass-produced goods."
The reason for this great success was the correct market analysis by Sinclair Research that the future of the home computer industry lay in the mass production of beginner-friendly devices with correspondingly low sales prices. The combination of technical innovations (ULA module) and cheap components for uncompromising price reduction, a built-in high-level programming language and massive advertising as a future product would have proven to be the right approach for successful marketing.
In addition, an entire industry of suppliers developed in the wake of the ZX81's success. Printed publications specifically on computer topics emerged and many well-known software manufacturers took their first steps. The computer market, previously reserved for specialists, had risen to become a serious branch with millions in sales in the entertainment industry (“More importantly, a new consumer electronics category was born”). The success of the ZX81 finally established Sinclair Research as an integral part of the ranks of home computer manufacturers that until then consisted exclusively of US companies such as Apple, Atari, Commodore and Tandy. For the founder of Sinclair Research and the driving force behind all the innovations, Clive Sinclair, the success should not only pay off financially. In addition to profit sharing in the millions, he was also awarded the title of English knight in June 1983 .
literature
- Don Thomasson: The Ins and Outs of the Timex TS1000 & ZX81. Melbourne House UK, 1983, ISBN 0-86161-118-7 .
- Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 .
- Rodney Dale: The Sinclair Story. Gerald Duckworth & Co., 1985, ISBN 0-7156-1901-2 .
- Stephen Adams, Ian Beardsmore, John Gilbert: All about Sinclair computers (Original title: The Complete Sinclair Database , translated by Domenica Ott). Birkhäuser, Basel / Boston / Stuttgart 1984, ISBN 3-7643-1625-X (= computer shop , volume 5).
Web links
- ZX-Team (community website with forum, German)
- ZX81 Museum (English)
- Zesarux (emulator for Linux systems, English)
- Timex / Sinclair 1000 Emulation (emulator for Java, browser-based, English)
Notes and individual references
- ^ Ian Adamson, Richard Kennedy: Sinclair and the "Sunrise" Technology. Penguin Books, 1986, pp. 103-105.
- ↑ Jason Crisp: Sinclair launches new personal computer costing only £ 70. Financial Times, March 6, 1981, p. 6.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , p. 100. Currently corresponds to a purchasing power of £ 270.03.
- ^ Deborah Wise: British company announces inexpensive computer. InfoWorld, November 2, 1982, p. 1.
- ↑ a b 8Bit Museum: The $ 149.95 personal computer. The $ 99.95 personal computer. Accessed March 31, 2014. Currently equates to a purchasing power of $ 367.87.
- ↑ First advertised by Sinclair Research Ltd. Germany in the magazine Funkschau issue 19 of September 18, 1981 on page 44 f.
- ↑ a b Jörg and Kerstin Allner: Computer Classics. Data Becker, 2003, ISBN 978-3-8158-2339-2 , p. 70. Currently corresponds to a purchasing power of 389.06 euros.
- ↑ a b Yoko Shibata: UK computer succeeds in Japan. Financial Times, September 30, 1982, p. 4.
- ↑ a b c d Sinclair Research: ZX81 personal computer. ( Memento of the original from December 14, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved March 25, 2014.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , pp. 80-82.
- ^ A b c d David Clutterbuck, Sue Kernaghan: The Phoenix Factor. Weidenfeld & Nicolson, 1990, ISBN 0-297-81123-1 , p. 146.
- ^ Martin Hayman: Interview - Clive Sinclair. Practical Computing, June, 1982.
- ^ A b Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , p. 103.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , p. 104.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , pp. 102, 104.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , p. 99.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , pp. 110 f.
- ^ Rodney Dale: The Sinclair Story. Gerald Duckworth & Co., 1985, ISBN 0-7156-1901-2 , p. 104.
- ^ Your Computer: Behind the BBC Programs. Edition March 1982, p. 24 f.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , pp. 116 f.
- ↑ Making sure it works properly. Sinclair User Magazine, Issue 2, 1982, p. 57.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , pp. 106-108.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , p. 105.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , pp. 107-111.
- ^ Rodney Dale: The Sinclair Story. Gerald Duckworth & Co., 1985, ISBN 0-7156-1901-2 , pp. 105-107.
- ^ Lynd Church: A piece of cake in Dundee. Sinclair User Magazine, Issue 2, May, 1982, p. 53.
- ↑ Your Computer Magazine advertisement , June, 1981, p. 22.
- ↑ a b Your Computer Magazine advertisement , June, 1981, p. 4.
- ^ Your Computer Magazine advertisement , June, 1981, p. 5.
- ^ Vic set to be success. Your Computer Magazine, June, 1981, p. 6.
- ↑ Don Thomasson: The Ins and Outs of the Timex TS1000 & ZX81. Melbourne House UK, 1983, ISBN 0-86161-118-7 , pp. 16, 50.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , p. 108.
- ↑ Peripherals can boost uses in education. Sinclair User Magazine, Issue 6, September, 1982, p. 12.
- ^ Rodney Dale: The Sinclair Story. Duckworth, London, 1985, ISBN 0-7156-1901-2 , pp. 106 f.
- ^ Smith adds to micro range. Sinclair User Magazine, Issue 4, July, 1982, p. 21.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , p. 111.
- ^ A b Rodney Dale: The Sinclair Story. Gerald Duckworth & Co., 1985, ISBN 0-7156-1901-2 , p. 107.
- ↑ Computerwoche: Sinclair goes on the road to success with the ZX81: A lot of performance for little money. January 22, 1982.
- ↑ Strong updraft. Chip, Issue 4, 1982, p. 55.
- ↑ Advertisement. Chip, Issue 8, 1982, p. 37.
- ↑ Why design if you can pinch it? Daily Telegraph, May 30, 1983, p. 8.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , pp. 133 f.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , p. 140.
- ↑ Paulo Henrique de Noronha: Micro digital consolida - na faixa dos pessoais. Micro Sistemas, Issue 12, 1982, pp. 30-32.
- ↑ Edna Araripe: TK85: novo pessoal no mercado. Micro Sistemas, Edition 3, 1983, p. 58 f.
- ↑ Ron Herdy: TK-82 Retrieved August 8, 2014.
- ↑ Power 3000, Lambda 8300 or PC8300. ( Memento of April 8, 2014 in the Internet Archive ) Retrieved March 30, 2014.
- ↑ Sinclair Clones. ( Memento of April 8, 2014 in the Internet Archive ) Retrieved March 30, 2014.
- ↑ 8-bit museum: Sinclair clones. Retrieved March 30, 2014.
- ↑ Bodo Wenzel: ZX97. ( Memento of the original from March 30, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved March 30, 2014.
- ↑ ZXGATE - Old Computers in new FPGAs. Retrieved March 30, 2014.
- ^ A b Don Thomasson: The Ins and Outs of the Timex TS1000 & ZX81. Melbourne House UK, 1983, ISBN 0-86161-118-7 , p. 14.
- ↑ Don Thomasson: The Ins and Outs of the Timex TS1000 & ZX81. Melbourne House UK, 1983, ISBN 0-86161-118-7 , p. 20.
- ↑ Don Thomasson: The Ins and Outs of the Timex TS1000 & ZX81. Melbourne House UK, 1983, ISBN 0-86161-118-7 , pp. 26-35.
- ↑ Don Thomasson: The Ins and Outs of the Timex TS1000 & ZX81. Melbourne House UK, 1983, ISBN 0-86161-118-7 , p. 13.
- ↑ Wilf Rigter: The ZX81 Video Display System. Retrieved March 30, 2014.
- ↑ WRX1K V1.0 1996 - HIRES ON A 1K ZX81 - wilf rigter (user.dccnet.com)
- ↑ ZX80 / ZX81 Video Mode True Hi-Res Graphics. ( Memento of March 14, 2013 in the Internet Archive ) Retrieved March 30, 2014.
- ↑ ZX80 / ZX81 Video Mode Pseudo Hi-Res Graphics. ( Memento of March 14, 2013 in the Internet Archive ) Retrieved March 30, 2014.
- ↑ Dietmar Eirich: Computer Periphery. Heyne, Munich 1985, ISBN 3-453-47058-3 , pp. 51-53.
- ↑ Sinclair ZX81 Data Tapes. Retrieved March 19, 2014.
- ^ Finding better ways of storing on tapes. Sinclair User Magazine, Issue 7, October, 1982, pp. 37 f.
- ↑ Stephen Adams, Ian Beardsmore, and John Gilbert: All About Sinclair Computers. Birkhäuser Verlag, 1984, ISBN 3-7643-1625-X , p. 119.
- ↑ Control system boosts power. Sinclair User Magazine, Issue 5, August, 1982, pp. 39 f.
- ^ Leading the way into new export market. Sinclair User Magazine, Issue 7, October, 1982, pp. 50 f.
- ↑ Wolfgang Taschner: Disk connection. Chip, Issue 11, 1982, p. 29.
- ↑ Plenty for users to choose from. Sinclair User Magazine, Issue 1, April, 1982, pp. 56 f.
- ^ FIZ into floppy action. Sinclair User Magazine, Issue 2, May, 1982, p. 7.
- ↑ Macronics: Macronics FIZ - floppy interface for ZX81 . Retrieved March 19, 2014.
- ↑ World of Spectrum: The LarKen 1000. Retrieved March 30, 2014.
- ↑ Metrimpex disc drive. Sinclair User Magazine, Issue 4, July, 1982, p. 48.
- ↑ Bits & Bytes: Sinclair printers. November edition, 1983, p. 2.
- ^ The end of the ZX Printer. Popular Computing Weekly, May 10-16. 1984, p. 1 f.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , pp. 106 f.
- ^ Commodore Horizons: Hot Printer December, 1985, p. 32.
- ^ Seth McEvoy: The Timex / Sinclair 2040 Printer. Compute !, Issue 42, November, 1983, p. 168.
- ↑ Getting into print. Sinclair User Magazine, Issue 28, July 1984, pp. 30 f.
- ↑ Ralf Knorre: The Seikosha GP 50 p. Computer Kontakt Magazin, issue 2, 1985 p. 22.
- ↑ Doing magic with the ZX81. Knaur, 1st edition, 1984, ISBN 3-426-03794-7 , p. 156.
- ↑ Sinclair ZX 81 Computer Course, Book 8, p. 202.
- ^ Sinclair's star add-on taken to pieces. Sinclair User Magazine, Issue 2, May, 1982, pp. 27 f.
- ↑ Haven has 16 colors. Sinclair User Magazine, Issue 7, October, 1982, p. 21.
- ↑ Kayde. Retrieved March 30, 2014.
- ↑ Memotech: Memopak HRG. Retrieved March 30, 2014.
- ^ Amplifier need sound knowledge. Sinclair User Magazine, Issue 21, December, 1983, p. 35.
- ↑ Sharon Zardetto Aker: The Zon X-81 Sound Generator. Sync Magazine, November / December, 1983, p. 60.
- ↑ QS Sound Vol. Sinclair User Magazine, Issue 2, May, 1982, p. 6.
- ↑ a b Memotech realizes the ZX81 potential. Sinclair User Magazine, Issue 11, February, 1983, p. 22 f.
- ↑ At Memotech we realize the potential of your ZX81 ... Sinclair User Magazine, Issue 12, March, 1983, p. 22 f.
- ^ Joystick from Kempston. Sinclair User Magazine, Issue 12, March, 1983, p. 27.
- ↑ Dietmar Eirich: Computer for reference. Compact Verlag, 1989, ISBN 3-8174-3564-9 , p. 212.
- ↑ Happy Computer: ZX81 Copy Protection - Hard times for pirates. Special issue 1, p. 122 f.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , pp. 105-108.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , pp. 104-108.
- ↑ The mini with many extras. Computer course, booklet 8, p. 205.
- ↑ Doing magic with the ZX81. Knaur, 1st edition, 1984, ISBN 3-426-03794-7 , pp. 107-112.
- ↑ Memotech: Z80 assembler. Retrieved March 30, 2014.
- ↑ a b c Winnie Forster: Computer and video game maker. Gameplan, Utting 2008, ISBN 978-3-00-021584-1 , p. 44.
- ↑ Judith Mirsoeff: Magazines for home computing New Scientist, December 9, 1982, p. 675
- ↑ Happy Computer: Spectrum-Tips Edition 3, 1984, p. 92.
- ↑ Andreas Lange: What archives, museums and libraries can learn from gamers - and vice versa. Retrieved February 23, 2014.
- ↑ Jeff Vavasour: Timex / Sinclair 1000 Emulation in a Browser Window. Retrieved March 30, 2014.
- ↑ Sourceforge: Zesarux - ZX Second-Emulator And Released for Unix. Retrieved March 30, 2014.
- ↑ a b Four ICs make a BASIC calculator. Chip, September, 1981, pp. 34-36.
- ^ David Tebbutt: Reviews - Sinclair ZX 81. Personal Computer World, Issue 6, June, 1981.
- ↑ Tim Hartnell: Review - The Sinclair ZX ~ 81. Your Computer Magazine, June, 1981, p. 14.
- ↑ Mikes Hughes: Sinclair ZX81 - Review. Practical Computing, June, 1981.
- ↑ Dietmar Eirich, Peter Herzberg: Computer Yearbook '85. Heyne, Munich 1984, ISBN 3-453-47042-7 , p. 34.
- ↑ a b Tony Smith: Sinclair ZX81: 30 years old. All hail the pioneer of UK home computing. The Register, March 4, 2011, accessed March 30, 2014.
- ^ Ian Adamson and Richard Kennedy: Sinclair and the Sunrise Technology. Penguin Books Ltd., 1986, ISBN 0-14-008774-5 , p. 259.
