Operating System Design/Case Studies/BSD
BSD, or Berkeley Software Distribution, is a UNIX operating system developed at the University of California, Berkeley. Started in 1977, it introduced many technologies still in use by operating systems today. It was the first OS of its kind to implement libraries supporting the Internet Protocol, allowing for easy read/write across a network.
Although the project died in 1995, it gave birth to multiple popular derivatives such as FreeBSD, NetBSD, and OpenBSD.