Berkeley Software Distribution

Berkeley Software Distribution (BSD) is the name of the UNIX derivative distributed in the 1970s from the University of California, Berkeley. The name is also used collectively for the modern descendants of these distributions.

In its infancy AT&T Bell Laboratories permitted Berkeley and other universities to use and extend the source code to their UNIX operating system. Berkeley used the software as a research base for investigations into operating system design through the 1970s and 1980s. Eventually, the systems that Berkeley students had developed for their research had replaced almost every component of the AT&T UNIX system, and in the early 1990s the full Berkeley source code was released publicly under the BSD License.

BSD pioneered many of the advances of modern computing. Berkeley's Unix was the first to include library support for the Internet Protocol stacks, Berkeley sockets. By integrating sockets with the UNIX operating system file descriptors, users of their library found it almost as easy to read and write data across the network, as it was to put data on a disk. The AT&T laboratory eventually released their own STREAMS library, which incorporated much of the same functionality in a software stack with better architectural layers, but the already widely-distributed sockets library, together with the unfortunate omission of a function call for polling a set of open sockets (an equivalent of the select call in the Berkeley library), made it difficult to justify porting applications to the new API.

Like AT&T Unix, the BSD kernel is a monolithic kernel, meaning that device drivers in the kernel run in ring 0, the core of the operating system. Early versions of BSD were used to form Sun Microsystems' SunOS, founding the first wave of popular Unix workstations.

Current Unix-like operating systems that descend from BSD include FreeBSD, NetBSD, OpenBSD, 386BSD, DragonFlyBSD and Apple's Darwin (and, hence, Mac OS X).

External links

• A timeline of BSD and Research UNIX can be found on FreeBSD's website (click on the latest revision number for the full tree)
• BSD For Linux Users, an article by Matthew D. Fuller, explains significant differences between BSD and Linux

Further reading

• Chris Dibona, Mark Stone, Sam Ockman, Open Source (Organization), Brian Behlendorf and J. Scott Bradner, Open Sources : Voices from the Open Source Revolution, O'Reilly & Associates, 1999, trade paperback, 272 pages, ISBN 1565925823; Online at http://www.oreilly.com/catalog/opensources/book/toc.html; Chapter on BSD - "Twenty Years of Berkeley Unix - From AT&T-Owned to Freely Redistributable"