Services of an OS:
1. Process Management
2. File Management
3. I/O Management
5. Security Management
UNIX OPERARTING SYSTEM:
In the mid-1960s, AT &T Bell Laboratories developed a new OS called Multics. Multics was intended to
supply large scale computing services as a utility; much like electrical power. In 1969 Ken Thompson,
Dennis Ritchie and others developed and simulated an initial design for a file system that later evolved
into the UNIX file system. The whole UNIX was rewritten in C. language in 1973.Today, UNIX is a
giant Os and is much powerful than most of its counter parts.
UNIX operating System is like a layer between the hardware and the applications that run on the
computer .It has functions that run on the computer. It has functions that manage the executing
applications. UNIX system is an OS, which includes the traditional system components. UNIX system
includes a set of libraries and a set of applications.
KERNEL is the heart of UNIX OS that manages the hardware and the executing process. The UNIX
system views each device as a file called a device file. It implements security controls to protect the
safety and privacy of information. The Unix System allocates resources including use of the CPU and
mediates accesses to the hardware. Application portability is the ability of a single application to be
executed on various types of computer hardware without being modified. This is one of the important
advantages of UNIX.
FEATURES OF UNIX:
Multitasking is the capability of the Os to perform various tasks simultaneously. i.e. A single user can run
multiple programs concurrently.
2. Multiuser Capability
Multiuser capability allows several users to use the same computer to perform their tasks. Several
terminals are connected to a single powerful computer and each user can work with their terminals.
Unix allows sharing of data. Every user must have a Login name and a password. So, accessing another
user‟s data is impossible without permission.
Unix is a portable because it is written in high level languages so it can run on different computers.
Unix supports communication between different terminals connected to the Unix server and also
between the users of one computer to the users of another computer located elsewhere in the network.
6. Programming Facility
Unix is highly programmable, the Unix shell programming language has the conditional statements and
control structures and variables.
UNIX ARCHITECTURE The functioning of Unix OS is handled in 3 ways. The closest layer is the
hardware, which provides the services to the OS. The Unix OS referred to Unix as the kernel, is the heart
of the Unix. The other layer is the shell, which acts as the mediator that translates the commands given by
the application programs.
It is the core of the OS. It controls all the tasks and carries out all the functions of an OS such as memory
and file management etc., and it keep track of the programs that are executing. It also handles the
information exchange between the terminals such as tape drives and printers etc.,