A microcontroller is sometimes described as a “computer on a chip” because it contains all the features of a full computer including central processor, in-built clock circuitry, ROM, RAM, input and output ports with special features'such as serial communication, analogue-to-digital conversion and, more recently, signal processing. The smallest microcontroller has only eight pins but some having 68 pins are also being marketed. In the last five years, the prices of microcontrollers have dropped by 80% and are now one of the most cost-effective components in industry. Being software-driven, microcontrollers greatly simplify the design of sophisticated instrumentation and control circuitry. They are able to effect precise calculations sometimes needed for feedback in control systems and now form the basis of all intelligent embedded systems such as those required in television and VCR remote controls, microwave ovens, washing machines, etc. More than ten times as many microcontrollers than microprocessors are manufactured and sold in the world in spite of the high profile that the latter enjoys because of the personal computer market. In Zimbabwe, extensive research is being carried out to use microcontrollers to aid the cost recovery of domestic and commercial solar installations as part of the rural electrification programme.