FROM …MULTICS ……..TO………LINUX

In early 1940’s computers were, batch systems which took enormous time for computing. Around mid 1960’s MIT and Bell laboratories came up with second generation of computers and MULTICS was introduced which was written in BASIC. .
It had numerous features intended to result in high availability so that it would produce a computing utility similar to the telephone and electricity services. Modular hardware structure and software architecture were used to achieve this. The system could grow in size by simply adding more of the appropriate resource—computing power, main memory, disk storage, etc. Separate access control lists on every file provided flexible information sharing and complete privacy when needed. It had a number of standard mechanisms to allow engineers to analyze the performance of the system as well as a number of adaptive performance optimization mechanisms.
The UNIX operating system found its beginnings in MULTICS (Multiplexed Operating and Computing System). In 1969 Bell laboratory pulled out and this project and this was taken by Ken Thompson. He liked the potential of MULTICS, but felt it was too complex and that the same thing could be done in simpler way. In 1969 he wrote UNICS which was simplified version of MULTICS. UNICS stood for Uniplexed Operating and Computing System. The problem was that UNICS had to be rewritten for every new machine which was launched.

UNIX-THE BABY BORN
The shortcoming of UNICS led Ken Thompson and Dennis Ritchie to join hands. Thompson wrote the whole source code in B language which did not gave the expected results so; Dennis Ritchie invented the C language which was right language at the right time. Then the whole source code was written in C language.
During that time PDP-11 was the most efficient and affordable mini-computer for commercial and educational purpose. The 6th and 7th versions of UNIX were released on PDP-11 and this helped in the spread of UNIX and this version came to be known as PDP-11 UNIX.

By late 1970’s there were many versions of UNIX. Among various different existing versions following are the most important ones:
BERKELEY UNIX
In university of Berkeley, California they developed their own new version from PDP-11 which was called 1BSD (Berkeley Software Distribution). It had many new added features like paging , virtual memory ,vi editor , csh shell. Hence many of the vendors like SUN , DEC preferred this version compare to the official system V .
SYSTEM V
Once written in C still, different disk drivers wanted their compiler to be written separately in assembly. Hence Steve Johnson came up with portable C compiler. In 1984 AT&T got the license circulated, system V which was followed by system V.2 and system V3.4 later.

But by 1995 most of the companies had license for UNIX. And many versions existed in the market. Hence there was a need to standardise it. So IEEE came up with a project POSIX (Portable operating system of UNIX). This included set of library conformant most of these procedures invoke system calls but few can be implemented outside the kernel.

MINIX-OPERATIONS SIMPLIFIED
UNIX itself was far more expensive. In quest of big money, the Unix vendors priced it high enough to ensure small PC users stayed away from it. The source code of UNIX, once taught in universities courtesy of Bell Labs, was now cautiously guarded and not published publicly. The big players in the software market failed to provide an efficient solution to this problem.
A solution seemed to appear in form of MINIX. It was written from scratch by Andrew S. Tanenbaum, a US-born Dutch professor who wanted to teach his students the inner workings of a real operating system. It was designed to run on the Intel 8086 microprocessors that had flooded the world market.
As an operating system, MINIX was not a superb one. But it had the advantage that the source code of 12,000 lines was available. For the first time, an aspiring programmer and hacker could read the source codes of the operating system, which to that time the software vendors had guarded. And one of them was Linus Torvalds. The structure of MINIX was very simple and the creator intentionally didn’t want to add more features in order to maintain its simplicity, there were constant requests from the programmers worldwide for the development of MINIX kernel but all of them were ignored by Andrew Tanenbaum.

It was then that a young finnish student Linus Torvalds came up with a fresh new kernel and approached the online community for further development of his project which came to be known as “LINUX”.