2BSD and 4.3BSD as examples of the UNIX system

This paper presents an in-depth examination of the 4.2 Berkeley Software Distribution, Virtual VAX-11 Version (4.2BSD), which is a version of the UNIX Time-Sharing System. There are notes throughout on 4.3BSD, the forthcoming system from the University of California at Berkeley. We trace the historical development of the UNIX system from its conception in 1969 until today, and describe the design principles that have guided this development. We then present the internal data structures and algorithms used by the kernel to support the user interface. In particular, we describe process management, memory management, the file system, the I/O system, and communications. These are treated in as much detail as the UNIX licenses will allow. We conclude with a brief description of the user interface and a set of bibliographic notes.