This week marks the 40th anniversary of the launch of the chip that unwittingly changed the world, Intel’s first microprocessor, the 4004.

Announced to the world in the 15 November 1971 issue of Electronic News, the claim to fame of this tiny 4-bit design, chugging along at what was even then was a fairly conservative 720 KHz, is that it is generally held to be that it was the world’s first commercial microprocessor.

Packing in 2,300 transistors (today’s PC microprocessors have up to 1 billion) its designers, lead by Intel employee number 12 Ted Hoff, were utterly convinced that the 4004 would transform the market for the most important business product of the day, deskside calculators. They were right.

Some have politely mocked the puny expectations of engineers working in a country still mired in the Vietnam war, and for which affordable personal computing was a speck on the horizon. But the 4004’s larger significance has to do with the company it helped to found, Intel.

The importance of Intel - which started life only three years before the 4004's launch - needs no introduction and was in large part thanks to a serendipitous business decision.

The Japanese customer for the 4004, calculator maker Busicom, agreed to give up some rights to its design in return for a lower unit price, and so a US giant got its hands if not on a large revenue stream at least an important slice of intellectual property. Busicom later went bust.

Years later, with pressure building on the company’s memory chip business, Intel resolved to take a more serious punt on microprocessors. When IBM came up with the business PC in 1981, the business sideline started by the 4004 suddenly became the business.

The microprocessor is now accepted as the most significant element in the industrialisation of computing second only to the transistor itself.  It was the Lego block from which immense computing power could be cheaply buried in any device from the PC to motor cars.

The 4004 might not have been the first microprocessor in everyone's book but it was the first ever put on sale and that counts for more.

And although nobody could care less now, it also helped to sell a hell of lot of expensive Japanese calculators.