Sinclair ZX Spectrum turns 40

[German]Today is a memorable day for some (older) computer enthusiasts. Because the 8-bit computer Sinclair ZX Spectrum was released exactly 40 years ago, and made some fellow citizens become "computer freaks". The following is a brief outline of the year 1982 and the years that followed.


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It was April 23, 1982, when the Sinclair ZX Spectrum 16/48k was introduced as a home computer. At that time I was professionally programming microprocessor systems with the Intel 8085 processor for the chemical industry, for measurement, control and regulation. It was a hot time, where I programmed in Assembler, Fortan and PL/M very close to the hardware and learned a lot. But at that time I got a rough idea of the developments in the field of home computers from home computer magazines. For more my time was not enough at that time.

The device

The Sinclair ZX Spectrum came probably in Great Britain at a price of 125 £ or 175 £ on the market and was the successor of the Sinclair ZX81. The processor was a Zilog Z80 (Z80A with 3.5 MHz). The calculator had 16 or 48 KB of RAM and 16 KB of read-only memory (ROM). The 16 KB versions could later be expanded to 48 KB by adding RAM. The device had a graphics output of 256 × 192 pixels in 15 colors. A commercially available cassette recorder is connected for storing data. Hardware expansions can be connected via a slot.

Sinclair ZX Spectrum
Sinclair ZX Spectrum, Bill Bertram CC BY-SA 2.5

The device was, like its predecessor, trimmed to cheap – compact housing, rubber keyboard and TV set as well as cassette recorder for storage had to be provided by the user. For the RAM components, defective memories were used in the 48 KByte version, where the defective memory banks were then blanked out, Wikipedia knows. The screen output, the sound output and the connection to the cassette recorder as memory was done by a special ULA device. About the graphics output, Wikipedia writes:  .

The graphic resolution is 256 × 192 pixels. For the color representation, 8 × 8 pixels are combined into blocks, so that effectively only a color raster of 32 × 24 blocks is available. In each block, the foreground and background color can be selected from 8 colors. In addition, the colors of a block can be brightened or blinked. The frame color can be selected separately from 8 colors. As an output device, a TV set is usually connected via the antenna input. A baseband video signal is also available at the extension port and could be taken and amplified with external hardware.

The ZX Spectrum had a small speaker for sound output. A 16 KByte ROM contained a BASIC interpreter, so people could program immediately. This led to the later availability of not only games, but also word processing, databases, various programming languages, assemblers and debuggers. The magazines for home computers (e.g. MC) printed the listings at that time, so that you could type in the program code yourself using the rubber keys. Wikipedia has some more details – e.g. Pascal was available for the device.


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I never have had a ZX Spectrum…

I confess, although I'm a bit older, I don't belong to the generation of Sinclair ZX Spectrum owners. I had flirted with it, but it was too much money for a device, with which one could not do so much. I bought (I can't remember the year exactly) come into possession of a predecessor model, the ZX 81, and picked up the daily frustration when saving and later trying in vain to re-read from the cassette recorder (see also Sir Clive Sinclair, the developer of the ZX81 died at 81).

Sinclair ZX-81
Sinclair ZX-81 with DIY power supply, source: own photo

At least the part caused me to spontaneous hardware tinkering – the photo above shows the self-made power supply for the device. And a 8 KByte RAM piggyback solution I had also built (see the following photo).

8 KByte RAM-Erweiterung ZX-81
Self-built 8 KByte RAM expansion ZX-81, Source: Own recording.

After the ZX 81 I left out the various Sinclair computers, but also the Ataris, Commodores etc.. Because since approx. 1984 I had to do professionally with MS-DOS-PCs. All mentioned devices had the disadvantage for me to be "game computers", with which I did not get on professionally.

So, when the devices became affordable, I bought an Amstrad PC with MS-DOS and a 20 MByte hard disk in 1987 (the floppy disk version, which used to be a bit cheaper, was also too puny for me). The Amstrad PC was a first real computer, with which I could test and complete software, which I developed professionally for my employer in dBase II, at home.

The Amstrad PC then led me astray, because with my experiments and experiences with the ZX 81, I could suddenly earn some money. Thats because I had written a disassembler in Basic on the ZX 81 "just for fun", but stopped the project later (it was no fun, because the memory was always too full and the saving and re-reading of the program code via cassette recorder turned into a night mare).

At some point I wanted to learn Pascal properly (I had taken a Pascal course at the Fernuni Hagen, but due to the lack of computers it was mainly a dry run). So I borrowed an IBM-PC over a holiday with a long weekend and organized a Turbo Pascal compiler. Then I ported the 8080 disassembler from Basic to Pascal, which was done as part of a weekend project. After that I could handle Turbo Pascal.

When I later had the Amstrad PC, the idea matured to write an article "how to build a Disassembler" and sell it to a magazine. At that time I also wrote the first computer book about Basic, because I wanted to compensate the purchase of the Amstrad PC with it. Anyway, I had suddenly tasted blood concerning "the writing".

And because I wanted to become rich and famous quickly, I continued to writer the next computer book, and the the next, and the next – till now it might be 300 titles. A Turbo Pascal title can also be found among them. Those were wild days – today we have the cloud, and people no longer know how computers "work". I never became rich and famous, all my lofty dreams were shattered by reality.

Today, I look back on those days with horror, because I realize: man, that was all 40 years ago when we started with this technology. I'm slowly getting to the point where grandpa can tell his grandchildren about the experiences in the potato war a century ago.


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