A computer is made of two main parts: the hardware and the software. The hardware part is the physical part of a computer and it consists of the mainboard, the processor, the memory, the keyboard, the HDD and FDD, the electric circuits, the mechanical devices and so on. On the other hand, the software is composed of all the programs which form the so-called intelligence of the computer. These programs ensure its functionality and the maximum exploitation of such a machine.
If we look at things from a functional point of view, we have the central unit, the peripheral pieces of equipment and the magisterial components. The central unit is the component which does all the processing. The peripheral pieces of equipment are those which are attached to the central unit, extending or improving its abilities. Last but not least, the interface units are basically the circuits and the devices which connect different components of the computer, may they be internal or external.
All computers have a variable number of peripheral and interface components, depending on their functional features. However, the configuration is pretty much the same in most of the cases if we take into consideration the fact that there are certain components you can not neglect or remove.
Most of the computers we have today still use the Von Neumann architectural structure, which consist of a basic configuration made of a single apparatus. This configuration includes the central unit, the control one, the arithmetic-logical unit, the external memory and the internal one and the input-output units.