In this text, UNIX will be used controversial with Linux. This tutorial is intended to make an introduction to the operating system concepts which will be discussed in lecture hours.
Understanding commands and processes
- when you enter a command it invokes a program. While this program is running it is called a process. It is important to grasp that although there is only one copy of a program held in the file system, any number of processes can be invoked which run this program.
- when the operating system is started after a boot, a single process is started. This process is the parent of all subsequent processes. Each process created on the system has a unique number, known as its PID, associated with it.
- when you login to the system a process is started to run your shell program. Any processes that are started from within your shell - such as entering a command - are the children of this process. A process can have many children, but only one parent.
- Every computer has an operating system.The UNIX operating system has three important features;