A stream input-output system

In a new version of the Unix operating system, a flexible coroutine-based design replaces the traditional rigid connection between processes and terminals or networks, providing interprocess communication.

Abstract

In a new version of the Unix operating system, a flexible coroutine-based design replaces the traditional rigid connection between processes and terminals or networks. Processing modules may be inserted dynamically into the stream that connects a user's program to a device. Programs may also connect directly to programs, providing interprocess communication. Introduction The part of the Unix operating system that deals with terminals and other character devices has always been complicated. In recent versions of the system it has become even more so, for two reasons. 1) Network connections require protocols more ornate than are easily accommodated in the existing structure. A notion of "line disciplines" was only partially successful, mostly because in the traditional system only one line discipline can be active at a time. 2) The fundamental data structure of the traditional character I/O system, a queue of individual characters (the "clist"), is costly because it accepts and dispense...