An operating system is an integral part of a computer system. The computer system can be viewed as being built from three general components: the hardware, the operating system, and the applications. The hardware includes pieces such as a central processing unit called a CPU, a keyboard, a hard drive, and a printer.
Applications are why we use computers; they use the rest of the system to perform the desired task. The operating system is the component that, on one side, manages and controls the hardware and on the other, manages the applications. When a computer system is purchased, it must have at least hardware and an operat ing system. The hardware is able to use one or more different operating systems. The operating system is necessary in order to manage the hardware and the applications.
The UNIX Operating System
UNIX, like other operating systems, is a layer between the hardware and the applications that run on the computer. It has functions that manage the hardware and functions that manage executing applications.
Unix is a very popular multi-user , multitasking operating system.
FEATURES
Multi User Capability
In a multiuser system,the same computer resources – hard disk, memory etc are accessible to many users. The users are given different terminals to operate from. A terminal , in turn , is a keyboard and a monitor , which are the input and ouput devices for that user. All terminals are connected to the main computer whose resources are availed by all users.
Multi Tasking capability
Unix OS is capable of carrying out more than one job at the same time. It allows the user to type in a program in its editor while it simultaneously executes some other command the user might have given earlier , say to sort and copy a huge file.
This is managed by dividing the CPU time intelligently between all the processes being carried out. Depending on the priority of the task, the operating system appropriately allots small time slots to each foreground and background task.
Portability
Unix has been written in C , hence it can run on machines from microcomputers to mainframe computers.
Security
Unix is a very secure operating system. Without the proper username and passwords, it is not possible to work on Unix. At the file level , there are read , write and execute permissions to each file which decide who can access a particular file ,who can modify it and who can execute it.
Stable and Reliable
A very reliable and stable Operating System. It is less prone to crashes.
Unix is available in many flavors like :
AIX (Advanced IBM Unix)
HP-UX ( Hewlett Packard Unix)
MINIX (Minimal Unix)
SCO UNIX
SOLARIS
XENIX
LINUX, etc
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