An operating system is closely attached to the hardware of the computer it runs on. It expands the computer's instruction set and controls its resources. To work, it must know a great deal about the hardware, at least about how the hardware appears to the programmer. Therefore, let us review computer hardware in brief as found in modern personal computers. After that, we can start getting into the details of what operating systems do and how they work.

Theoretically, a simple personal computer can be abstracted to a model resembling that of following figure. The CPU, memory, and I/O devices are all joined by a system bus and communicate with one another over it. Modern personal computers have a more complex structure, involving several buses, which we will look at later. For the time being, this model will be adequate. In the following sections, we will briefly review these components and look at some of the hardware problems that are of concern to operating system designers. Unnecessary to say, this will be a very compact summary. Many books have been written on the subject of computer hardware and computer organization, two famous ones are by Tanenbaum (2006) and Patterson and Hennessy (2004).

computer hardware review


operating system, memory, i/o devices