...live long and prosper...
Technically not "the first" but truly
the number one home computer.
The 'micro' that introduced millions of people to computers.
ZX Spectrum

The legend

The Sinclair ZX Spectrum is not the computer that wrote history in computers; it is the computer that defined computers altogether. Yes, the Apple I might be the mythical first complete computer, and yes, Sinclair had already produced two computers before it, but the ZX Spectrum that shaped and defined the "home computers" class single-handedly.
Ultimately, the ZX Spectrum is quite possibly the most successful computer of its era, taking into account the myriad of clones that were created, most unlicensed in eastern Europe -- at the time behind the "iron curtain" and, consequently, under technological embargo by the western world.

The original Spectrum was released in two versions: one featuring 16kB of RAM and one with 48kB (yes, those are kilobytes, a.k.a. 1/1,024th of a megabyte), built-in speaker, no floppy drive support, no on/off switch (!) and even no monitor output; instead, it only had an RF modulator to connect to a plain TV set; the "operating system" was the BASIC programming language with minor Spectrum-specific extensions.

Making history

The single drive behind Sinclair's creations was the design and production of a computer that would be affordable to everyone. The main reason computers were stuck outside people's homes was cost. Electronics were getting cheaper throughout the '70s but not cheap enough to allow a decent computer to be built cheaply. Take the Apple IIe for example, released in January 1983 and priced at a whopping $1400. Compare that to the Spectrum's April 1982 price: £125 (16k version). Yes, that's not a typo, the Spectrum cost 10 times less and, even taking into account inflation, it was quite affordable.

The same could be said, of course, about Sinclair's two previous computers, the ZX80 and ZX81, but neither of these quite fits the bill. The "Speccie", as it became known, was the first small and affordable computer that featured colour, a "close enough" to normal keyboard (more on that soon), upper and lowercase characters and sound! Notice how these features sound ridiculous nowadays; for 1983, though, the combination was a killer.
Indeed, demand was so great that Sinclair couldn't make enough and Spectrums were back-ordered for several months!

Money savers

Since cost was the main factor, every aspect of the Spectrum's design had to be the most economical of all possible choices. Consequently, the engineers had to innovate and think outside the box, in order to meet the goals.
Here are some key points that made a difference.

  • Keyboard: the one chosen was not a normal keyboard with solid keys and switches, but rather a rubber/membrane hybrid, rubber mat on top (similar to TV remotes) with a standard 3-leaf keyboard membrane underneath. The reason, according to Sinclair himself, was to minimise the number of parts; while a 'normal' keyboard consists of hundreds of parts (key caps, springs, switches, etc), Spectrum's keyboard only has three: the rubber mat, the membrane and the metal plate covering the mat. Less parts means simpler assembly but also less things that could not work and eventually be costly for the company through product returns. The downside was that the keyboard was clearly not suitable for speed-typing, touch typists or editors. Some even went so far as to describe it as having a "dead flesh" feel. Thankfully, I've yet to type on a keyboard made of dead flesh so I cannot vouch for the validity of those reports; personally, though, I had no problem typing on the Speccie's keyboard.
  • Memory: the circuitry for the RAM chips utilising the extra 32kB of the 48kB model was designed so that faulty 64kb chips could be used as 32kb, by selecting chips which had faults only on half of their capacity and deactivating that faulty half! That, of course, meant that Sinclair could buy faulty chips from RAM manufacturers at super-low cost and thus have a profit margin whilst keeping product prices low.
  • Hardware: the Spectrum used absolutely no secondary processors but only one ASIC (Application-Specific Integrated Circuit) known as the ULA, which handled pretty much everything: graphics, DRAM refresh, storage and video output. While other machines used specially designed ICs for graphics, sound, memory management, storage and more, the Spectrum made do with none! On its board, apart from the RAM and some glue logic, there are only two major players: the Z80 CPU and the ULA (Uncommitted Logic Array)!
  • Ports: the back-side of the Spectrum was rather spartan; the only ports were those for connecting a television set, a cassette recorder for storing and loading data and an exposed edge of the board itself, with terminals exposing various signal lines - including most of the CPU's address, data and control buses directly! There were no serial or parallel ports, monitor output, printer port or any other connection that other computers usually had. No ports means less internal circuitry but also no connectors to install!
  • Storage: the only storage device natively supported was the tape recorder; rather than include a disk drive or a controller for one and force the users to buy one, the only requirement was a plain cassette recorder, a device that was extremely common at the time. The downside was that programmes took many minutes to load, something which led to a lot of jokes like putting the Spectrum to load and going to make tea.
  • Graphics: in order to save memory, the display colours were stored in a low-resolution matrix. While the pixel resolution of the Spectrum was 256x192 pixels, the colour resolution was 32x24 blocks of 8x8 pixels, thus forcing each block to share the same foreground and background colours. This was particularly evident in games, where the 'blockiness' of the colours became a telltale of the Spectrum.
  • Codewords: another memory-saving scheme was the way BASIC programmes were stored and input. Instead of storing the entire word (e.g. RANDOMISE or CIRCLE), each command was assigned a one-byte code and stored in memory thusly. Also, each keyword was assigned to a key on the keyboard (or combinations of keys); for example, PRINT was assigned to the 'P' key, LOAD to 'J', while THEN was under "Symbol Shift" + 'G'. Thankfully, all keywords were printed on the keys themselves (or directly above and below), so even experienced users usually had to scan the keyboard in order to find the keyword they needed.
  • Switches: it is unclear how much Sinclair saved, however the Spectrum had no "on-off" switch! In fact, no Sinclair computer ever had one! Even worse, the original Spectrum had no "reset" button either -- only later models came with one. As a result, users had to unplug the computer in order to switch it off or even reset it!

The end result is a computer which has now passed to the realm of legend, partly because of those shortcomings and not in spite thereof.

Indeed, just about everyone remembers the rubber keyboard, the distinctive "beeeeeep-chirp beeeeeep-chirpychirpychirp" sounds produced during loading or saving programmes or the blocky-coloured graphics, while anyone who had ever tried typing a programme on the Spectrum remembers the keyword-specific keys. The most common BASIC command being "PRINT", most users, trying to type in the command, ended up with "PRINT rint" on the screen and an error-indicating beep when they pressed the "ENTER" key.
Despite all the peculiarities and quirks of the computer, though, it outsold every other computer of its time, coming second only to the Commodore 64, mostly due to Sinclair's absence from the US market and the poor reception of Sinclair's official clone for the americas, Timex.

Expand and extend

The extremely spartan nature of the Spectrum opened the door to an entire ecosystem of third-party hardware developers, who quickly jumped in to provide the Spectrum with everything that it lacked by design. Soon after its release, expansion devices started appearing, ranging from very simple joystick interfaces to extremely sophisticated multifunction devices.
Sinclair released two such interfaces themselves, the unimaginatively named "Interface 1" and "Interface 2". The former featured a microdrive interface (Sinclair's custom storage device based on magnetic tape), serial port and local network ports, while the latter was a much simpler device, featuring two joystick ports and a ROM cartridge connector.
The most famous expansion devices, though, were the "Disciple" and the "+D", two multifunction devices made by "Miles Gordon Technologies" (MGT). The Disciple was similar to the Interface 1 and featured a floppy disk drive controller, printer port, network ports compatible with Sinclair's, two joystick ports and perhaps most importantly, a 'snapshot' button which allowed storing the contents of the entire memory on disk. The +D interface was a simplified version of the Disciple, having only the FDD controller, printer port and the snapshot button.

Another noteworthy device is the Opus Discovery, an expansion unit which came with a (big) case housing one or two 3.5" floppy disk drives, its circuit board and power supply for itself and the Spectrum and featured a floppy drive controller (obviously), joystick port, printer interface and monochrome composite video out.

Other peripherals that appeared included printer interfaces, speech synthesisers, sound generators, drum machines, midi keyboards, even mouse interfaces and digitisers, while there was a plethora of after-market cases for the Spectrum which invariably included a normal keyboard.

At the time, though, the most wanted interface - even more than an FDD interface - was the "Multiface One" by "Romantic Robot", a device which allowed freezing whatever programme was running, examination and alteration of the main memory, saving the entire memory on tape, floppy disk or microdrive and, of course, resuming the interrupted programme. In case you still don't get it, it allowed freezing a game and (apart from making a 'save' at any point) hacking the memory for extra lives, energy, money, ammo or whatever else was in short supply in each game! Needless to say, anyone who had both the Multiface and an FDD interface was the envy of everyone.

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