The topic of interprocess communication techniques is broad, challenging and dynamic. All but the most basic operating systems provide methods for processes communication. Early on, UNIX supported a number of rudimentary process communication constructs (such as lock files, signals and pipes). In the early 1980s, facilities such as message queues, semaphores, and shared memory were added to the mix by AT&T with its release of UNIX System V. Somewhat concurrently, the Berkeley Software Distribution added support for Internet protocols (4.3BSD) and the socket interface as a communication construct. By the mid-1990s, threads and multithreaded programming techniques were making significant, permanent inroads into the UNIX mainstream.
Along the way, UNIX spawned innumerable UNIX-like operating systems. One such operating system was MINIX. MINIX, written by Andrew S. Tanenbaum, is a small (about twelve thousand lines) PC version of UNIX. MINIX was presented as a pedagogical tool to permit the user to gain a better understanding of the inner working of a UNIX-like operating system. As all of the operating system source code was provided, the user could tinker with the code and refine its functionality. As a university student, Linus Torvalds' exposure to MINIX led him to develop a more robust UNIX-like operating system called Linux. In brief, Linux is a freely distributed hybrid version of UNIX. Linux system administration is BSD-like while its programming environment has a definite AT&T flavor. A number of commercial versions of Linux populate the market. These versions bundle Linux with a variety of other operating system related utilities and software packages. One of the more widely distributed commercial versions is Red Hat Linux. Red Hat Linux includes Richard Stallman's GNU project C (gcc) and C++ (g++) compilers.
