The IBM PC, Commodore 64 and the ZX81 were among personal computers to hit the shelves in 1981. The first IBM PC had a 4.7Mhz processor and the cheapest model had 16K of memory. Disk drives were an optional extra but each 5.25inch disk could hold 160K of data. Mobile phones were the thing of Tomorrow's World in their chunky infancy - with national UK networks not available until 1985.