Operating Systems: Concurrent and Distributed Software Design

2.5. Operating system invocation and protection

We shall again use the high-level abstraction 'process' to capture the notion of dynamic execution. When we come to implementation examples we shall distinguish between 'process' and 'thread'.

There are two ways of invoking operating system services:

• a process may make system calls;

• a user may give commands to a process running a command interpreter program that causes the process to make system calls.

Once a process is executing a program it may request operating system services by making system calls. The set of system calls is the interface to the operating system module through which the operating system functions are invoked. Section 3.2 explains in detail how this entry into the operating system ...