Overview of the Unix Operating System

UNIX is a multi-user, multitasking, time sharing operating system. It was developed in 1969 in Bell Laboratories by Ken Thompson and Dennis Ritchie. It was the first operating system to be written in C language. That is, why it becomes easy to move it to a new machine-portability. This was an important reason for its large popularity and availability on a wide variety of systems.

Characteristics of UNIX

Portability.

Open system.

Rich and productive programming environment.

Communication.

Multi-user capability.

Multitasking.

Components of UNIX

Kernel

Command Interpreter

File System.

Kernel: - It is known as the base operating system. It controls the computer resources. When the user logs on, the kernel runs init and Getty to check if the user is authorized has the correct password. Kernel provides the following function:

Process scheduling.

Memory management.

Device management.

File management.

System call interface.

Process synchronization (make them show exactly the same time) and inter process communication.

Operator console interface.

The utility programs and UNIX commands are not considered as part of UNIX kernel. Kernel consists of layers closest to the hardware that are the for the most part protected from the user. Kernel communicates directly with hardware. The kernel does not deal directly with a user.

Command Interpreter: - This is a utility program and his called a shell. It interacts with the user and translates the user's request into action on the part of the kernel and other utility programs. Each user opens one shell on logging on. The shell translates typed command in to action; therefore it is termed as command interpreter.

The UNIX File System: - The file system is responsible for storing on disk drives and retrieving and updating this information directed by the user.

Characteristics of UNIX file system:-

Having a hierarchal structure.

Having ability to create and delete files.

Dynamic growth of files.

Consistent treat of file data.

Protection of file data.

The treatment o peripheral devices or files.