The inventor of the pocket calculator and creator of the groundbreaking ZX Spectrum home computer passed away at his home in London today (Thursday) after a long illness, according to his daughter Belinda.

The entrepreneur Sir Clive Sinclair, inventor of the pocket calculator and creator of the groundbreaking ZX Spectrum that helped popularize home computing, has left us. His home computer stood shoulder to shoulder with the Tandy Color Computer and the Commodore 64 as one of the three primary options for people who wanted an affordable computer in their homes.

Belinda Sinclair, 57, told the Guardian: “He was a rather amazing person. Of course, he was so clever and he was always interested in everything. My daughter and her husband are engineers so he’d be chatting engineering with them.”

Sinclair left school at 17 and worked for four years as a technical journalist to raise the funds to found his company Sinclair Radionics. From there, he worked out how to build a series of calculators in the 1970’s that were light enough and small enough to fit in a shirt pocket at a time when most calculators were huge 20 pound monstrosities that took up most of a desk.

After first hitting the market with hobbyist audio amplifier kits, his first home computer was the ZX80, a black-and-white computer with no sound capability, that one hooked up to one’s television. It had no moving parts apart from the keys, and only 1k of programming memory. It ran on a Z80 microprocessor, and a whole subculture of home computing sprung up around the little machine, with dozens of magazines supporting each new arrival into the marketplace. The Sinclair itself had no fewer than eighteen magazine titles. In the third year selling them, he made roughly 14 million pounds, and was knighted that year for it.

Clive Sinclair was successful making remarkable things like digital watches (the first to do so) and pocket televisions (also the first to do so). Some of his other inventions, however, did not take hold. He believed that the Sinclair C5, a curious electric vehicle that was something like a cross between an electric scooter and a go-kart, would be the Next Big Thing. It launched as a product in 1985, with Sinclair predicting sales of 100,000 units in the first year. Unfortunately that wasn’t close to true, with the product failing because of concerns about exposure to the elements, and being below the eye line of most drivers. Sinclair sold his computer business the following year to Amstrad.

Belinda Sinclair said: “It was the ideas, the challenge, that he found exciting. He’d come up with an idea and say, ‘There’s no point in asking if someone wants it, because they can’t imagine it.’”

Outside inventing, his interests included poetry, running marathons and poker. He appeared in the first three seasons of the Late Night Poker television series and won the first season final of the Celebrity Poker Club spinoff.

He is survived by Belinda, his sons, Crispin and Bartholomew, aged 55 and 52 respectively, five grandchildren and two great-grandchildren.

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