that there were already 40,000 users of the ZX80 and that by the time the series was broadcast there were likely to be upwards of 100,000 ZX81 users (which turned out to be an underestimate by over 400,000 – an indication of how the ZX81's success exceeded even Sinclair's expectations). A prototype ZX81 was demonstrated to BBC representatives in January 1981, while Sinclair's local rival Acorn Computers put forward their proposed Proton computer, a design – of which a prototype did not yet exist – based on the Acorn Atom. To Sinclair's dismay, the contract to produce the BBC Micro went to Acorn, which launched the machine in January 1982. Paul Kriwaczek, the producer of The Computer Programme, explained his reservations in a March 1982 interview with Your Computer: Sinclair was critical of the BBC's decision, accusing it of incompetence and arrogance. Shortly after Acorn won the BBC contract the Government issued a recommended list of computers, including the BBC Micro and Research Machines 380Z, that schools could purchase, with the aid of a grant, for half price; Sinclair's computers were not included on the list. Sinclair responded by launching his own half-price deal, offering schools the chance to buy a ZX81 and 16 KB RAM pack for £60, plus a ZX Printer at half price, for a total cost of £90. As the cheapest Government-approved system was £130, this was an attractive offer for some schools and about 2,300 bought Sinclair's package, although 85% adopted the BBC Micro. Development and manufacture The development of the ZX81 got under way even before the ZX80 had been launched. Sinclair's chief engineer, Jim Westwood, was given the task of improving the ZX80's hardware to reduce the number of components and thus bring down the cost. He also sought to fix some of the more annoying problems with the ZX80. Westwood and his colleagues found that the component count could be reduced greatly by combining eighteen of the ZX80's chips into a single uncommitted logic array (ULA), a type of general-purpose chip full of logic gates that were connected up as the customer required during chip manufacture. This short-lived technology of the day was cheaper and quicker than the design of a customised logic chip, which typically required very high volumes to recoup its development cost. Ferranti produced the new chip for Sinclair, who hailed Westwood's design as a triumph of innovation: "The