What is a Sinclair Spectrum?
Released in 1982 as a direct rival to Acorn's BBC range of educational computers, the Sinclair ZX Spectrum was a true home computer at an affordable price. It loaded games from a standard cassette player and produced a display on the family television set. Unlike its competitors, the Spectrum was small and black, with rubber keys and a small buzzer for making simple beeping noises - and it was amazingly successful.
The hardware
The Spectrum was based on a combination of ULA (uncommitted logic array) and 3.5 MHz Z80 processor, and initially had 16 kilobytes of RAM (usable memory). This was later increased to 48 KB, which rapidly became the standard.
The screen display measured 256 × 192 pixels, a high resolution for its time, and supported eight colours at two brightness levels, totalling fifteen colours (since bright and dull black were identical). The display was divided into 24 rows and 32 columns of "character cells", each 8 × 8 pixels and capable of containing any two of the basic eight colours (or attributes), as long as they were at the same intensity. This led to some "attribute clash", one of the most endured and loved features of the hardware: where two coloured objects collided, their attributes would overlap, giving the impression of coloured squares.
Sound was similarly simple and to the point: a buzzer capable of outputting one channel of beeping. The BEEP command was used to drive it from BASIC, but clever machine code routines could produce multi-channel effects and music, which no other computer of the time could rival without dedicated sound hardware.
The BASIC
Spectrum BASIC was more or less unique, as was the method of programming. Keys on the keyboard were imprinted with BASIC keywords, which meant that a single keypress (such as P) could produce an entire keyword (PRINT). The use of shift keys made further keywords available. It was a quirky system, but easy to learn. This style of coding was the standard for all Spectrums prior to the 128K machine.
For more information, see History of Sinclair BASIC.
History of the Spectrum
Although intended as a serious business and educational machine, the Spectrum quickly gained a devoted following of gamers. Because Sinclair had wisely incorporated the BASIC programming language, a legion of bedroom programmers arose almost overnight, advertising their home-grown games cheaply in magazines. Many of today's programmers owe their careers to the Spectrum, having moved from BASIC to Z80 assembly language; and top software houses such as Rare and Bullfrog cut their teeth in the home computer market by writing top-quality Spectrum games.
The Spectrum continued to grow, not only with new incarnations, but with an increasing selection of peripherals. You could buy printers, mass storage devices, joysticks, light-pens, and light-guns - all in the same sleek rounded black style. It was a hobbyist's dream.
In 1984, the Spectrum became the Spectrum+, with a typewriter-style keyboard housing for the still popular 48K machine. The new keyboard kept the "Sinclair" feel and was adequate for single-key programming, if not for touch-typing.
The 128K Spectrum followed in 1986. A clever memory paging mechanism gave this machine a full 128 kilobytes of RAM. The BASIC benefited from a "silicon disk" or RAM disk, allowing programs to be saved to temporary memory almost instantly, and a PLAY command which controlled the three channels of the new AY-3-8912 sound chip.
Later in 1986, Sinclair Research was sold to Amstrad Consumer Electronics, who re-released the 128K machine as the Spectrum +2 with a new ROM, a grey case with a more professional keyboard (reminiscent of the Amstrad CPC), and a built-in cassette recorder. Many considered this to be the death of the Sinclair Spectrum, but Amstrad did eventually address issues with the machine's hardware when they produced the Spectrum +3, complete with 3" disk drive.
Commercial software (mostly games) continued to be released for the Spectrum until the early 1990s. Even now, in the twenty-first century, the Spectrum is almost a household word - and the enthusiasm for it seems likely to continue well into the future.