Initially, computers operated with valves similar to electric lamps. When in the 50s were introduced transistors (devices the size of a pea, constructed with materials such as silicon or geranium), significantly decreased the size of computers. The first had been of gigantic size. A new development occurred when the transistor was replaced, in the 70s, for the silicon chips, also known as microchips. These tiny disks, only a few millimeters in diameter, fulfill the function of millions of transistors. Each has its own CPU, memory and input and output areas of information. Within a computer, microchips for memory and data processing are placed on a board and connected by copper wires.
In the chips is stored and processed information. The microprocessor is the central chip that controls the computer and in which does arithmetic-logic unit. The control unit coordinates the functioning of computer components. The input and output registers are memory units smaller than main memory, which stores data and results with operating the arithmetic-logic unit. All are connected by internal buses. There are three types of buses: the address, the control and data.