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As an active UNIX user i felt a thread on UNIX,its flavours would be great.i would highly be indebted to anyone who contributes to this thread about the present,past of UNIX.flavours,LINUX etc.the following thread attempts to give an introductory talk on UNIX and its features.Xelios i hope you read this,this might help you out in understanding of basics of UNIX and its various flavours.(If you do know a bit,plz share your experience with me about the topic).:)
Welcome to the world of UNIX.once the domain of wizards and gurus,today UNIX has spread beyond the university and laboratory to find a home in Global corps and small internet servers alike.this capability to scale up and down,to accomadate small installations or complex corporate networks with little or no modification is the only charracterstic of UNIX that is responsible for its popularity.

Unix is built on rich,powerful and yet simple elements.Although many more recent operating systems have borrowed concepts and mechanisms of UNIX,those who are most familiar with the legacy Mainframe enviornments,or those whose experience is limited to mostly single user oriented enciornments may find UNIX intimidating at first.At its base ,UNIX is both Simple and elegant,with a consistent architecture that,in turn,underlies and guides the design of its many application programs and languages.

so what exactly is the <b>UNIX</b>?
UNIX like other operating systems is a layer between hardware and the applications that run on the computer.Essentially three layer Binds to Form a complete UNIX system.
1.)A Kernel(Innermost software layer)
2.)A SHELL(Interpreter)
Thus from above you can see that kernel is the one that directly interacts with the hardware,shell is an interface to understand commands of a user.

in mid 1960s,AT&T BELL LABS was participating in an effort to build a new Operating system.this was called Multics.in 1969,Bell Labs pulled out of Multics effort and members Ken Thompson,Dennis Ritchie et al developed and simulated the development into what later evolved to UNIX file system.

as the team continued to experiment,they developed their work to do text processing for patent dpt at AT&T.afterwards C (yes the famous C)was developed with joint efforts of Kernigham and Ritchie on and for UNIX,the UNIX thus was re-written in C itself.this is what made it an open system that it is today.
As a then-regulated company,AT&T wasnt allowed to market computer systems.Nonetheless,the popularity of UNIX grew with internal use at AT&T and licensing to univesities for EDUCATIONAL use.By 1977,comercial licenses for UNIX were being granted.later versions developed at AT&T included SYSTEM III several releases of SYSTEM V.All the versions of UNIX based on AT&T work require a license from the current owners,UNIX SYSTEM LABORATORIES.

<B>BSDs(Berkeley Software Distributions)</B>
In 1978(As far as i remember,but it could be 1979 also),research group turned the distributions of UNIX to UNIX support group(USG),which had distributed an internal version called programmers workbench(thats what it was called).in 1982,USG introduced System III.,and then on SYSTEM V etc.

The computer science group at University of California at Berkeley(UCB) developed of what was called populary BSDs.the original PDP-11 had 1BSD AND 2BSD.Support for DEC VAX compuetrs was introduced in 3BSD.Then continued its VAX tie-up with 4.0BSD,4.1BSD,4.2BSD,4.3BSDs etc.

Because of multiple versions,cross pollination between variants many features have diverged in the different vesions of UNIX.Standardization has hence become a need,a powerful one.
The Institute of Electrical and Electronic Engineers(IEEE)created a series of standard committees to create standards for "An Industry-Recognised operating systems Interface standard based on UNIX operating system".the POSIX.1 committe standardizes the C library interface used to write programs for UNIX.the POSIX.2 committee standardizes the commands avalable for general user and so forth.

the US govt has specified a series of standards based on XPG and POSIX.currntly FIPS 151-2 specifies the open systems requirements for federal purchases.
for more information on the subject you may like to log on to:
Several version of UNIX and UNIX like systems have been made that are free or inexpensive and also include source codes.These versions are particularly attractive to the modern-day hobbyist,who can now run a UNIX system at Home for little investments and with great opportunity to experiment the OS or make changes to suit his own needs.

An early UNIX like system was developed by famous A.S.Tanaenbaum(the author of great bestseller computer Networks),it was called MINIX by him.

TODAY,the most popular version of UNIX is undoubtdly Linux.Linux was designed by Linus Torvalds to be a free replacement for UNIX and it aims for POSIX compliance.Linus during his early days didnt have enough money to buy a UNIX os.but he was learning C language during those days.this enabled him to write and compile the source code for his own kernel program wich he christened as Linux and put it on his colleges Network.later on with various ,infact millions of users add-ons and improvements it went on to become the choice of Millions of users,from small to mid-sized ISPs and Web-servers.

However,if you"re an active windows user,then i"d suggest you start with DRAGON-LINUX,it can work as a folder inside your windows and you dont need partitioning etc,however that would involve skipping various important concepts like swap partition etc.

in the end i would say that the thread aims to introduce UNIX as a whole to Science Forums.i would appreciate any replies from any one.any one can share experiences with me.i"ll come up with a little add-on to this thread to describe exactly how shell kernel boots and how the whole system works.later,for now ...

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