Essential Guide to Computing: The Story of Information Technology, The

The Structure of the Operating System

As shown in Figure 5.5, modern OSs use several internal layers. Most of system supervision (memory management and allocation of CPU time) is handled in the part of the OS that is called the kernel. Sitting on top of the kernel is another layer, usually called something like user section. This is the part that deals with programs and with the user. We'll discuss each of these layers in turn.

The Kernel

There are three principal reasons for separating the OS into a kernel and a user section. First, creating discrete layers makes it possible to isolate the part that deals with users (meaning in this case the application programs that users control) from that which deals with critical hardware management such ...