The BBC series of microcomputers were designed and built by Acorn Computers Ltd in the 1980s. In 1981 the British Broadcasting Corporation were launching their Computer Literacy Project and were looking for a machine to link it with. Acorn got the contract and the machine, then known as the Proton, became the BBC Microcomputer. The term "BBC Micro" is generally used to refer to the first four machines (Model A, B, B+64 and B+128) whilst "BBC Master" refers to its replacement series (Master 128, Master Turbo, Master ET, Master 512 and Master Compact). This category deals with the emulation of a BBC Micro or Master on a different platform, such as a PC or Apple Mac.