Early Home Computers

From the early ’80s, a large number of manufacturers were creating cheap computers built around off-the-shelf 8-bit CPUs, typically the MOS 6502 or the Zilog Z80. Competition was fierce; one manufacturer cut their margins so fine that they needed to keep the money from their customers in their bank account earning interest for a month before they could afford to buy the components.
Many of these machines were used primarily for gaming, but machines of this class introduced a generation of school children to computer use and programming. In Britain, this was encouraged by the Government of the time, through initiatives such as “Micros in Schools” and “IT82: The Information Technology Year”.

Amstrad

Amstrad was founded by Alan Sugar in 1968, with the name Amstrad being a contraction of Alan Michael Sugar Trading. The contrast between Sugar and other names in the microcomputer industry of the time is striking: whereas the other figures, such as Clive Sinclair and Chris Curry (of Acorn), were in the computer business because they were enthused by the new technology, Sugar was purely interested in the potential money that could be made from the devices. This approach to microcomputers can be seen in Sugar’s response to Sinclair, who had “started talking about the wonders of the technology in his Spectrum machine”, during negotiations to acquire Sinclair’s computer business: “For God’s sake, Clive, I don’t care if they have rubber bands in them, as long as they work” [1].

Amstrad’s first model of microcomputer was the Amstrad CPC464 (the Colour Personal Computer, with 64 kilobytes of memory), released in April 1984. Designed in Britain around the Zilog Z80 microprocessor, the machine was actually manufactured by the Japanese company Orion in South Korea, unlike both Sinclair and Acorn, who had their machines manufactured primarily in the UK. The computer utilised custom gate arrays, which was designed and manufactured to Amstrad’s specification by the British company Ferranti, with Italian firm SGS available as a second source [1, p131]. However, the computer, as well as its software, were designed in the UK. The design of the hardware was outsourced to MEJ Electronics, a small partnership run by two electronics engineers. The operating system (a BASIC intepreter) was created by another small partnership, Locomotive Software. Both groups continued to work for Amstrad, later producing the hardware designs and software for the PCW series of “word processors” and Amstrad’s first IBM PC clones.

The CPC464 was one of the first home microcomputers in the British market to be supplied with a ‘monitor’ (which used a standard television tube) as standard, as well as an integrated cassette recorder. Alan Sugar described the reasoning behind the choices made:

“Our first computer was a very typical Amstrad concept. We sat down and observed all this computer stuff. And we saw what people were actually buying with computers. They needed lots of cables and cassette decks, and then they had to plug it into a television. …I decided that the Amstrad philosophy is an all-in-one piece, so we would present our product as complete with a keyboard, cassette mechanism and monitor … It looked like a mug’s eyeful for the old man when he walked into Dixons. He looks at this thing, with its whacking great big keyboard and a monitor, and he has visions of a girl at Gatwick airport where he checks himself in for his holidays. And he thinks, ‘That’s a real computer, not this pregnant calculator thing over there called a Sinclair’” [1, p123]

The company later introduced the PCW, a word processor/microcomputer hybrid, with the “Locoscript” word processor program written by Locomotive Software, the CP/M operating system and a BASIC programming language interpreter. Amstrad was one of the few manufacturers to use the 3” floppy disk format. This decision was made for purely financial reasons: the drives and disks “were being sold cheaply because the 3” format was in the closing stages of an ultimately losing battle against 3 1/2” disks” [1, p124].

Mark New

References

[1] David Thomas. Alan Sugar: The Amstrad Story. Century, 1990.

Sinclair Computers

Sir Clive Sinclair, the founder of Sinclair Research, was a habitual inventor and entrepreneur who received much press attention in the 1980s (not all good: for example, the coverage related to Sinclair’s C5 electric vehicle). Sinclair’s first company, Sinclair Radionics, produced radio sets using rejected computer transistors bought from Plessey Components. The company later moved into the calculator market, producing a pocket calculator called the Sinclair Executive for the price of £79, and then a few years later the Sinclair Cambridge — described by Sinclair in an interview as “the world’s first single chip scientific calculator — the first cheap one too” [3] — for £43.95 fully assembled.

Later, after a brief flirtation with the digital watch, Sinclair moved into the manufacture of computers. Firstly, at Sinclair Radionics (which Sinclair later left after the Government-run National Enterprise Board acquired a stake in the firm) the design project for the NewBrain was started: this computer was to become first proposed design for the BBC microcomputer. However, the company was unable to deliver a completed product on time, meaning that the Corporation had to look for another design elsewhere. After leaving Sinclair Radionics, Sinclair founded Science of Cambridge, which was later renamed Sinclair Research. This company designed and sold a new computer kit, known as the MK14. Initially designed by employee Ian Williamson, the MK14 used the National Semiconductor Microprocessor (National SC/MP). The design of the kit was eventually changed to use National Semiconductor components throughout. This primitive kit computer was not as impressive as its rival Nascom 1: it did not come with a full keyboard, for a start. However, the machine became more popular than was expected at launch, probably aided by an “extravagant advertising campaign” [1]. In a theme that was to run through the entire history of Sinclair Research, the company was initially unable to keep up with demand.

ZX80 and ZX81

The innovative sub-£100 microcomputer cited by so many is the ZX80. It was produced in 1980 by Science of Cambridge after the relative success of the MK14, which had “proved to Clive Sinclair that microcomputers were a worthwhile product” [2]. Initially sold by mail order, Sinclair was yet again unprepared for the demand. Newspaper advertising by Sinclair in 1980 stated that “inside a day, you’ll be talking to it like an old friend!” and that “if computers interest you—and today, computers should interest everybody—you’ll find the ZX80 totally absorbing”. While this advertising blurb may have not have encouraged everybody, Sinclair had sold over 20,000 ZX80s by September of that year [2]. However, the machine was described by Ian Adamson and Richard Kennedy as not representing “a development of existing technology, merely its competent application” [1]. For instance, the machine only came with 1kB of RAM, and was not capable of handling floating-point arithmetic.<!-- compared with others? -->

The successor to the ZX80 was the ZX81, which was the first Sinclair microcomputer to be sold in high street shops [1]. The computer sold very successfully in the stores of W. H. Smith, despite the initial scepticism of many of a number of buyers at the company: “Negative feedback from the shopfloor was rapidly reversed by an overwhelmingly enthusiastic market response. In the year following the ZX81’s appearance in the high street, W. H. Smith sold in excess of 350,000 machines and banked a net profit of around £10 million … This figure assumes a ZX81 purchase price of £69.95 and the 40 per cent retailer’s discount quoted by W. H. Smith” [1]. The ZX80 and ZX81 were certainly very popular: their low price, if not their level of functionality, made them a popular choice, as the sales figures at W H Smith indicate. Companies quickly appeared that offered add-on peripherals for the machines; indeed, W H Smith themselves offered an own-label cassette recorder for the ZX81. A sign of the popularity of the Sinclair computers — and indeed of microcomputers in general — was that 10,000 people attended a computer fair dedicated to Sinclair computers in January 1982 [2]. The media quickly started a microcomputer frenzy, hailing them as a massive technological advance: for instance, The Sun described Sinclair as “the most prodigious inventor since Leonardo” (cited in [1]).

However, not all were positive about the Sinclair machines. For instance, Paul Kriwaczek, producer of the BBC’s The Computer Programme, described the ZX81 as “a throwaway consumer product” [1], because its capacity for expansion was limited. A Sinclair machine was ultimately not chosen for the BBC’s Computer Literacy Project; instead, the more advanced ‘Proton’ designed by Acorn Computers was chosen as the basis for the BBC Micro. In addition, the decision to use a membrane keyboard with ZX80, ZX81 and Spectrum was controversial, being more difficult to use than a conventional keyboard: one group of contemporary commentators wrote that “the only group to benefit from this policy has been the peripheral manufacturers, who have provided a wide range of alternative keyboards” [1].

ZX Spectrum

The ZX81 was followed by the Sinclair ZX Spectrum. This was the first Sinclair microcomputer to be eligible for the British Government’s Micros in Schools grant. Available in two versions (with either 16 or 48 kilobytes of memory, with the 16kB model being upgradable by purchasing an expansion pack), the Spectrum was arguably the company’s most successful product. A number of peripherals were offered for the Spectrum, including the ZX Microdrive: a tape based device, where “the cartridges … contain a loop of 200 inches of magnetic video tape on which 85K of data can be stored. Although considerably slower and less flexible than a disc system, the Microdrive can nevertheless load a 48K program in about 4 seconds” [1]. This was a considerable improvement compared to the slow, and often unreliable, cassette tape based system. The Spectrum spawned an entire ‘cottage industry’ of individual programmers, producing software for the machine: mainly games, but also some productivity software as well.

{To follow: Sinclair QL, bought by Amstrad}

Mark New

References

  • [1] I. Adamson and R. Kennedy. Sinclair and the “Sunrise” Technology. Penguin Books, 1986.
  • [2] R. Dale. The Sinclair Story. Duckworth, 1985.
  • [3] C. Langdon and D. Manners. Digerati Glitterati. John Wiley and Sons, 2001.

The BBC Micro

The BBC Micro was, for much of the ’80s, the iconic educational computer in the UK. It was originally created by Acorn, a Cambridge firm, for the BBC’s Computer Literacy Project. This combined a hardware platform with a series of television programmes teaching programming. A range of pages on the BBC’s CEEFAX teletext service were devoted to distributing source code for the examples for this show. An external teletext decoder for the BBC allowed teletext pages to be loaded into the system: with a modem, the decoder could also be used to access British Telecom’s Prestel viewdata service.

Two models of the BBC, the Model A and Model B, were sold for £299 and £399 respectively: the Model A containing 16kB of RAM, and the Model B 32kB. Additional models of the original BBC containing more memory were later introduced, such as the B+ and B+128, with 64 and 128kB of RAM respectively.

The BBC had basic vector graphics capabilities and was commonly used with an implementation of Logo for teaching geometry. Logo was a dialect of Lisp designed for controlling a ‘turtle’ which would take commands like forward or backwards with a distance, or left or right with an angle. The turtle would travel over the screen drawing a line behind it, unless the ‘pen up’ command was delivered. In many schools, a physical turtle was used (although it often looked nothing like a turtle), which could draw shapes on a large sheet of paper.

Although Logo was often used for teaching, it was not supplied with the machine. When starting the machine, the user was presented with a prompt into which BBC BASIC code could be entered. This dialect of BASIC, designed by Sophie Wilson (then Roger Wilson) was designed to support structured programming, with named subroutines and other complex flow control structures. It also included an inline assembler, allowing 6502 assembly language to be interleaved with BASIC code, and for BASIC code to generate assembly allowing users to write compilers easily. The advanced features of BBC basic are credited as being one of the major reasons for Acorn winning the BBC contract, although their comparatively advanced hardware features are also likely to have been a significant factor.

The input/output (I/O) capabilities of the BBC made it popular in school technology labs years after the other capabilities of the machine had been superseded. A number of ports, including analogue input, were available and could easily be programmed from BASIC. These were used for controlling a variety of external devices, from seven-segment displays to robot arms. The systems could also be networked using Econet, Acorn’s proprietary networking interface.

Acorn later released two additional computers based on the BBC Micro design: the Acorn Electron and BBC Master. The Electron was essentially a low-end version of the BBC Micro, intended for use at home rather than school and designed to compete with the other low priced systems available at the time (e.g. the Sinclair Spectrum and Amstrad CPC464). The BBC Master, introduced in 1986, was an improved (and mostly backward-compatible) evolution of the original BBC design. The Master came with 128kB of RAM installed as standard. The software produced by the BBC’s Domesday Project was designed for the Master: to use the software, schools needed to purchase a videodisc player and trackball, which could be added to the Master using its expansion ports.

David Chisnall and Mark New

Further Reading

The Dragon 32

To be written...

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