On This Day - 30th July

Clive Marles Sinclair was born on 30 July 1940 near Richmond, Surrey. He would become one of Britain's best-known technology entrepreneurs and inventors. In 1961 he founded Sinclair Radionics, initially producing electronic kits and later becoming famous for products including calculators, digital watches and televisions.

Sinclair moved into home computing through Science of Cambridge, which produced the MK14 kit computer, before establishing Sinclair Research. The company went on to produce the ZX80, ZX81 and ZX Spectrum, helping to bring affordable home computing to a mass British audience. The ZX Spectrum in particular became one of Britain's most successful home computers and played an important role in the development of the British computer and video-game industries.

Sinclair's interests extended well beyond computers. His products included the Sinclair Executive pocket calculator, the Black Watch digital watch, the TV80 pocket television and the Sinclair C5 electric vehicle. His willingness to pursue ambitious and sometimes unconventional ideas made him one of the most recognisable figures of Britain's early consumer-electronics and home-computing revolution.

Sinclair was knighted in the 1983 Queen's Birthday Honours for his contribution to the personal-computer industry. He died on 16 September 2021, aged 81.

In July 1961, Clive Sinclair founded Sinclair Radionics, the company that would establish him as one of Britain's best-known electronics entrepreneurs. Initially operating from a small premises in London, the company began by developing and selling electronic products, including radio kits, amplifiers and other low-cost electronic equipment. Sinclair's approach was to make technology affordable to a much wider audience by keeping products small, simple and inexpensive.

Sinclair Radionics went on to produce a wide variety of innovative products, including the Sinclair Executive pocket calculator, one of the world's first genuinely pocket-sized electronic calculators. The company also developed the Black Watch digital watch and the company's early television products. Although Sinclair Radionics eventually ran into financial difficulties, its work laid much of the groundwork for the Sinclair computer business.

The company's experience in designing low-cost electronic products would prove particularly important when Sinclair entered the emerging home-computer market. Following the financial difficulties of Sinclair Radionics, Clive Sinclair established Sinclair Research, which went on to produce the ZX80, ZX81 and ZX Spectrum and transform the British home-computer market.

The **ZX Microdrive** was Sinclair Research's compact storage system for the ZX Spectrum and ZX81. Announced in 1983, it was intended to provide a much faster and more convenient alternative to cassette tape, while remaining considerably cheaper than a conventional floppy-disk system. Each Microdrive cartridge was a small removable loop of magnetic tape, allowing programs and data to be stored and retrieved without the long loading times associated with ordinary cassette recordings.

A Microdrive cartridge could store approximately **85KB of formatted data**, although the actual usable capacity depended on the way the storage was formatted and the system software being used. Data transfer was considerably faster than cassette, with the Microdrive capable of loading and saving files in seconds rather than minutes. Cartridges could also hold multiple files, making the system much more useful for serious programming and data storage. The Spectrum's operating system provided commands for handling Microdrive files, while the BASIC language included support for loading and saving programs and data to the drives.

The Microdrive was not simply a storage device but part of Sinclair's wider expansion system for the Spectrum. The drives connected through the **ZX Interface 1**, which also provided networking and an RS-232-compatible serial interface. Up to eight Microdrives could be connected in a daisy-chain arrangement, giving a substantial amount of online storage for the period. The combination of Microdrives, networking and communications made the Interface 1 a significant expansion for users who wanted to move beyond the Spectrum's original cassette-based design.

Despite its advantages, the Microdrive had limitations. The cartridges used a continuous magnetic tape loop rather than the random-access media used by floppy disks, and the mechanism and cartridges were relatively delicate. Reliability could also be affected by worn or contaminated cartridges and drives. Nevertheless, the Microdrive was an ambitious and distinctly Sinclair solution to the problem of bringing fast, affordable mass storage to a low-cost home computer. It became an important part of the Spectrum ecosystem and helped demonstrate how far the machine could be expanded beyond its original specification.