Introduction to UNIX

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UNIX was originally developed at Bell Laboratories as a research project by a small group of people. UNIX is one of the most powerful, versatile and flexible operating systems in the computer industry. This is because of its ability to run a wide variety of machines starting from microcomputers to super computers, and its portability. It is also capable to run on a single computer or in a network. Today's popular Unix OS are SunSolaris and HP (Hewlett-Pacakrd) Unix.

Unix is a command-line interface and it is a multi-user operaring system. The prompts to enter Unix commands are $, %, >. In its later releases, Unix operating system provides graphical user interface, ex. MOTIF and Openlook, based on windows standards called X-Windows. However, knowledge of UNIX is required for operations that are not covered by a graphical program, or for when there is no X windows system, for example, in a telnet session. The below figure shows an X-windows screen shot.

The Unix operating system is made up of three parts; the kernel, the shell and the programms. The kernel of UNIX is the hub of the operating system: it allocates time and memory to programs and handles the file storage and communications in response to system calls. The shell acts as an interface between the user and the kernel. When a user logs in, the login program checks the username and password, and then starts another program called the shell. The shell is a command line interpreter (CLI). It interprets the commands the user types in and arrange for them to be carried out. The commands are themselves programs.

Read Introduction to DOS from here

Read Introduction to LINUX  from here

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