UNIX Part 1

Unix is an operating system. Just like Microsoft Windows unix had GUI (graphical user interface) for easy to use environment. knowledge of UNIX is required for operations which aren't covered by a graphical program, or for when there is no windows interface available, for example, in a telnet session.

TYPES OF UNIX

There are many different versions of unix. The most popular ones are Sun Solaris, Linux and MacOs X.

THE UNIX OPERATING SYSTEM

Its is made up of three parts:

1.The Kernel (is the core of the system)

2.The Shell

3.The programs

The Kernel allocates time and memory response and handles the filestore and communications for any system response.

The shell acts as a interface between the user and the kernel.

For example consider the following example to understand how a kernel and shell works:

When an user types a command to remove a file (rm myfile)… the shell searches the file store to locate that file containing the program rm, and then sends the request to kernel to execute the program rm on myfile. When the process rm myfile is complete the shell then returns % prompt (unix prompt) to the user.

Here is another example:

When you log in to the system the Kernel checks if your Login and password is correct and then runs a shell Program for you to interact with it.

The shell is a program that the kernel runs for each user which sets commands for execution.

It can have several shells and one kernel

By having the kernel in control, it is also possible for one user to run several shells. The kernel remains in control of all shells and programs