Unix, standardization of OS and POSIX

The most developed OS, such as "OS/360" (IBM company), "SCOPE" (company "CDC") and "MULTICS" (MTI and Bell Labs company) completed in the 1970th years, provided a possibility of execution on multiprocessor computers.

The eclectic nature of development of OS led to increase of the crisis phenomena, first of all, connected with excessive complexity and the sizes of the created systems. OS were badly scalable (simpler could not use all opportunities of large computing systems; more developed non-optimal were performed on small or could not be performed on them at all) and it is total incompatible among themselves, their development and improvement dragged on.

Conceived and implemented in 1969 by Ken Thompson with the assistance of several colleagues (including Dennis Richie and Brian Kernighan), Unix OS ("Unix"; originally "UNICS" that beat the name "MULTICS") incorporated many lines of earlier OS, but had a number of the properties distinguishing it from most of predecessors:

• simple metaphorics (two key concepts: computation process and file);

• component architecture: the principle "one program — one function" plus powerful tools of binding of different programs for the solution of the arising tasks ("cover");

• minimization of a core (the code which is executed in the "real" ("exclusive") mode of the processor) and quantity of system calls;

• independence of hardware architecture and implementation in a machine-independent programming language (the Si programming language became "by-product" of development of "Unix");

• standardization of files.

"Unix", thanks to the convenience first of all as the instrumental environment (development environment), was warmly accepted at first at the universities, and then and in the industry which received a prototype of uniform OS which could be used on the most different computing systems and, moreover, could be quickly and with the minimum efforts is postponed for any again developed hardware architecture.

In the late seventies of the XX century employees The University of California in Berkeley entered a number of improvements to the source codes UNIX, including work with protocols TCP/IP. Their development became known under a name BSD — "Berkeley Software Distribution".

The task to develop independent (from copyright of Bell Labs) implementation of the same architecture was set also by Richard Stollmen, the founder of the GNU project.

Thanks to competition of implementations the architecture of Unix OS became the actual industry standard in the beginning, and then found the status and the standard legal — ISO/IEC 9945.

The OS following the standard or relying on it call "POSIX - compatible" (word usage "Unix similar" or "Unix family" meets more often, but it contradicts the status of the Unix trademark belonging to consortium "The Open Group" and reserved for designation OS, strictly following the standard) thanks to the name of the standard — POSIX. Certification on compatibility with the standard costs some money because of what some systems did not undergo this process, however POSIX - are considered as compatible, just because it so.

Systems which are based on the latest version of "Unix", released Bell Labs ("System V") on developments of the University of Berkeley ("FreeBSD", "OpenBSD", "NetBSD") and also GNU/Linux OS developed regarding utilities and libraries by the GNU project and regarding a core — the community headed by Linus Torvalds belong to Unix-like OS.

Standardization of OS guarantees a possibility of painless replacement of OS and/or the equipment at development of the computing system or network and cheap transfer of the application software (strict following to the standard assumes full compatibility of programs at the level of a source text; because of profiling of the standard and its development some changes nevertheless are necessary, but transfer of the program between POSIX - the compatible systems costs on orders cheaper, than between alternative) and also succession of experience of users.

Effective deployment of the Internet in the nineties became the most noticeable effect of existence of this standard.