An Introduction to Unix
- UNIX is an OS which was developed in the 1960s and since then it has been under constant development ever since.
- By Operating system, we intend the collection of programs which make the computer work. Unix is a stable , multiple user system for servers, desktops and laptops.
- UNIX has a GUI similar to Microsoft Windows and it provides an easy to use environment. Knowledge of unix is essential if you are willling to use such a system or when there is no windows interface available.
- There are various versions of UNIX with some of the popular varieties being Sun Solaris, GNU/Linux and MacOS X
UNIX Operating System
- The UNIX is made up of 3 parts: the kernel, the shell and the programs.
- The kernel is the hub of the OS:
- The kernel allocates time and memory to various programs and handles communications in response to system calls.
- The shell is the biggest interface between the user and the kernel.
- When a user logs in, the program checks for the username and password, and then initiates another program termed as the shell.
- The shell is basically a command line interpreter(CLI) which interprets the commands the user types in and manages to carry them out.
- The commands are programs themselves that on terminations gives the user another prompt.
- The expert user can customise his/her own shell and users can use different shells within the same machine.
- The tcsh shell has features to help user input commands.
- By typing the name of a command and by pressing the Tab key , the tcsh shell displays the rest of the name automatically.
- In UNIX everything is a file or a process
- A process is an executing program which is identifed by a unique PID(Process Identifier)
- The collection of data is a file. The file is created by users using a text editor, running compilers etc.