In comparison, the ZX80 featured a monochrome display, no sound output, a measly 1KB of memory and an awkward membrane keyboard. To hamstring things further, the processor at the machine’s heart was required to do everything, from reading keyboard inputs to updating the screen, and it obviously couldn’t multitask, so the display would flick off when a key was pressed or the CPU was busy executing a program, which, to all intents and purposes, ruled out animated games. Only a couple of years separated the release of the ZX80 and the Spectrum, but there’s almost a generation gap between the two machines – a clear sign of the speed at which the personal computer market was moving in the early Eighties. Component costs were tumbling, innovation was rocketing, and computers that were actually useful in an everyday sense were invading homes and businesses. The ZX80 may have been quickly superseded, yet it played a key role in demystifying and popularising the micro, particularly in the UK. It also provided Sinclair with the impetus to expand the ZX line. After all, we wouldn’t even be banging on about the Spectrum were it not for the groundwork laid by the ZX80.
The development of the ZX80 can be traced back to 1978. In June that year, Clive Sinclair’s micro-computing arm Science of Cambridge released the MK-14, a kit computer with a calculator keypad and an 8-digit LED display that retailed for £40. Although the assembled kit was of little practical use, it was the perfect, low-cost training aid for students or hobbyists who wanted to learn about microprocessors. It’s difficult to determine just how many kits were sold – reported figures vary from 10,000 to 50,000 – but it was successful enough to show Sinclair that computers were a market that could be tapped, even if it was just to raise funds for other ventures within his business.
In 1979, following Sinclair’s resignation from his Radionics firm, of which the government’s National Enterprise Board had taken a controlling interest, he focused his attention on Science of Cambridge and began to plan a successor to the MK-14. Looking to the US, he saw the big three machines – the Apple II, the Tandy TRS-80 and the Commodore PET – and while they were proper desktop computers designed for real-world application, they were also hugely expensive. The retail prices were even more prohibitive in the UK, where import dealers would, in time-honoured tradition, simply swap the dollar sign for a pound sign and effectively double the price. Sinclair’s notion of selling inexpensive consumer products certainly didn’t embrace computers retailing at £1,000, nor even half that amount. In fact, he distanced himself from the Newbrain micro project while still at Radionics because its planned scope meant that he wouldn’t be able to sell it cheap enough to attract a wide enough market. So he set about developing the ZX80 as a capable, low-cost computer that he could retail for that magic, consumer-pleasing price of £100.
It was a noble aim, but Sinclair was a businessman and he knew that any product still had to turn a tidy profit. To keep the component budget down, long-standing Sinclair engineer Jim Westwood put together a simple hardware design based around the Z80A processor, which consisted entirely of off-the-shelf chips. It wasn’t particularly innovative – and the aforementioned flickering display was an unfortunate flaw – but it was a considerable step on from the MK-14. The board and its 21 chips were housed inside a moulded plastic two-piece case designed in-house by John Pemberton. The most curious element of the ZX80’s industrial design was the pressure-sensitive ‘keyboard’, which was basically a plastic sheet with 40 keys printed on it, and by prodding a key, contact would be made with the circuit board tracks beneath and the key press would be registered. It was cheap and not entirely cheerful, particularly after prolonged use.
Further compromises were made with the internal software. A 4KB ROM was provided to store the ZX80’s system software, including BASIC, and the unenviable task of trying to cram so much onto such a tiny chip was handed to John Grant of Nine Tiles. Using the ANSI Minimal BASIC standard as reference, Grant spent the summer of 1979 creating the very first version of Sinclair BASIC. In order to meet the 4KB limit, some commands and functionality had to be dropped, with one of the main drawbacks being that the ZX80 could only deal with whole numbers. The dialect was aimed very much at beginners and introduced the one-touch keyword entry system that would become the hallmark of Sinclair BASIC. This idiosyncratic approach ensured that commands could not be mistyped, and to further reduce the chance of errors on code execution, the syntax of each line was checked for faults as it was entered. Considering the restrictions of the ROM chip, Grant’s work was mightily impressive and must surely have helped establish BASIC as the language of choice for home micro manufacturers.
The ZX80 was officially launched at a London computer fair in February 1980 and made available to buy direct from Science of Cambridge. Sinclair wanted to market the first ready-assembled computer to break the £100 threshold, and that’s exactly what he did. An assembled ZX80 retailed for £99.95, and if you were handy with a soldering iron, you could buy the kit for £79.95. The first review appeared in the April 1980 issue of Personal Computer World magazine. “The ZX80 offers an ideal introduction to computing,” wrote David Tebbutt. “It makes BASIC easy to learn, it’s small enough for it not to be intimidating, and it’s cheap enough that, should you decide computing is not for you, you can give it away, sell it or whatever.
The ZX80 appears to be a well thought out machine both in terms of hardware and software, leaving me very little to say except that I hope Mr Sinclair and his merry men of Cambridge can cope with the expected flood of orders.” Perhaps Tebbutt had previous experience of Sinclair’s haphazard mail order operation, because the orders did indeed flood in and, predictably, many customers had to wait months for their machines to arrive.