3.Clones of Unix
5.Unix file system
6.Why use Unix.?
•The Unix OS was developed (based on
Multics & CTSS operating systems) by Ken
Thompson at the AT&T Bell Laboratories in
•He wanted to create an multi-user operating
system to run “space wars” game.
•Ken‟s philosophy was to create an operating
system with commands or “utilities” that
would do one thing well i.e. UNIX
•The first versions of UNIX were
written in “machine-dependent”
program (such as PDP-7).
•Ken Thompson approached Dennis
Ritchie, developer of C
language, and in 1973 they compiled
UNIX in C to make operating
system “portable” to other
Features Of Unix
•Multi-user and Multitasking OS
•Hierarchical file system
•The building block approach
•Pattern matching (wildcard characters)
•Unix is said to be an open system.
•Most of the servers are on Unix
Clone of UNIX (LINUX)
• Debi an
•Includes device drivers for computer hardware
devices, e.g., graphics cards, network cards, disks
•A device driver is a program that allows computer
programs to interact with hardware devices
•CPU and memory management
•File system management
•Implements system calls that can be used by
•application programs and system utilities
Unix File system
•Files contain data, program code, etc
•File names cannot have the „/‟
character in them.
•Directories Contain files and other
A link is a pointer reference to another
•Devices Allows applications to access
Why Use Unix?
•One of the biggest reasons for using
Unix is networking capability.
•With Unix, networking capability is
simply part of the operating system.
•Unix is ideal for such things as world
wide e-mail and connecting to the
•Unix was written in a machine
•Full multitasking with protected memory.
•Multiple users can run multiple programs each at
the same time.
•Very efficient virtual memory
•Access controls and security.
•Available on a wide variety of machines - the
most truly portable operating system.
•Unix is a well-stocked toolbox
•Unix also provides a stable and secure platform
•Do not require direct user interaction with the
•Designed for the programmer, not the
•Much use of special keyboard characters little typos have unexpected results
•Unix is not a very user-friendly operating
•An application program written for one
version of UNIX may not run on other