THE FIRST microprocessor to be made commercially was the 4-bit Intel 4004 of 1971 and today 4-bit devices are still the commonest, since they can be used in toys, washing machines, heating-system controllers and a wide variety of household goods, where their word size is no handicap. By 1980 a variety of cheap 8-bit microprocessors, such as the Rockwell 6502 and the Intel 8080/8085 series had come on the market. Faster 8-bit microprocessors and microcontrollers followed and more and more facilities were added to fill what were seen as gaps in a highly-competitive market. The 8-bit microcontroller is now replacing the 4-bit device, even in applications requiring relatively little processing power. 16-bit, 32-bit and even 64-bit devices have become available and are used mostly for specialised purposes such as PWM motor (mostly 16-bit microcontrollers) and robotic control. The robotics field in particular has urgent need of fast microcontrollers with large word sizes. Table 22.1 lists some of the devices, which is only a small sample of those available now and in the past.