What are the components and shells of UNIX?

Components of UNIX

Generally, a computer system consists of four main components, called hardware, application programs, operating system, and users.

• Hardware − Physical devices are nothing but which we can touch and feel.

• Operating system − It allows the user to communicate with the hardware.

• Application − There are software programs which give some functionality to the user.

• User − One who gives instructions to the computer to perform an operation and accepts the result from the computer.

If there is no hardware, the system does not have computing capability.

If there is no operating system, the user cannot connect to the hardware parts to perform the operation.

If there are no applications, there is no use of computers.

UNIX Commands

Now let us see the UNIX commands which are as follows −

• Commands − This will instruct the OS to do tasks. For example, ls files.

• Kernel − It is the main area of the operating system.

• File system − Storage of files in hard disk. For example, folder

• Interface − It will give libraries. For example, stdio.

Unix Shells

Generally shell is a software program that acts as a mediator between the kernel and the user. It reads the commands and interrupts by sending requests to execute a program. So, the shell is known as a command interpreter.

The two main shells used in UNIX are as follows −

Bourne shell

Every shell will have a default prompt, for Bourne shell default prompt is ‘$’. The sub categories are as follows −

• Bourne again shell (bash)

• Korn shell (ksh) etc.

Bourne shell is a choice for writing scripts that can be used on different versions of UNIX.

C shell

The default prompt for C shell is ‘%’. The difference in C shell is a command processor. It allows the users to type commands. The different shells are as follows −

• TENEX C Shell (Kcsh)