STUDY OF UNIX OPERATING SYSTEM

OPERATING SYSTEM

An Operating System is a set of programs that

􀁸 Functions as an virtual machine by presenting an interface that is easier to program than the underlying hardware

􀁸 Acts as resource management through orderly and controlled allocation of the processors, memories, and I/O devices among the programs competing for it.

OS TYPES

1. Single User—The system will have its own hard disk, memory, CPU and other resources all dedicated to a single user. Eg. MS-DOS

2. Multi User—The users having access to a multi-user system will have just a terminal and a keyboard. The other resources such as hard disk, printers are centrally located.

The user is expected to simply hook onto his account, perform the work, disconnect and leave quietly. Eg. UNIX

UNIX FEATURES

1. Multi-user system—Multi-user capability of UNIX allows several users to use the same computer to perform their tasks. Several terminals [Keyboards and Monitors] are connected to a single powerful computer [UNIX server] and each user can work with their terminals.

2. Multi-tasking system—Multitasking is the capability of the operating system to perform various task simultaneously, i.e. a user can run multiple tasks concurrently.

3. Programming Facility—UNIX is highly programmable, the UNIX shell has all the necessary ingredients like conditional and control structures, etc.

4. Security—UNIX allows sharing of data; every user must have a single login name and password. So, accessing another user’s data is impossible without his permission. 

5. Portability—UNIX is portable because it is written in a high level language. So,UNIX can be run on different computers.

6. Communication—UNIX supports communication between different terminals of the same server as well as between terminals on different servers.

Apart from these features, UNIX has an extensive Tool kit, exhaustive system calls and Libraries and enhanced GUI (X Window).