Work on AT&T Corp’s Plan 9 operating system, which it launched last week (CI No 2,710) – began back in 1987, and the thing is designed to run across desktop terminals, and symmetric multiprocessing file and network servers that could be connected by a variety of network topologies. Processing, file serving and storage are services shared ov er a single protocol built atop the network, each service being defined as a rooted tree of files, such that where an application actually runs, in terms of the resources it requires, becomes irrelevant. Each process has a local file name space that contains attachments to all services the process is using and thereby to the files in those services. Breaking the file server away from the processor server provides greater security possibilities, the company claims, because as a separate machine that can be accessed over the network only by a standard protocol and can only serve files, it cannot run programs. All system objects present themselves as named files manipulated by read-write operations. All files can exist locally or remotely and respond to the standard protocol. The file system name space – the objects visible to a program – is dynamically adjustable for each program running on a particular machine. In Unix almost everything is a file. In Plan 9 everything is a file, said the company. Plan 9 comes with its own C and other compilers plus commands and program tools originally developed in Unix. They include Alef, which provides threads, inter-process and inter-machine communication. Acid is a programmable debugger which understands multiple-process programs that could be running on multiple machines. Acme is a user interface in which any word on the screen can be interpreted as a command by clicking on it, and any string can specify a file to be displayed. Plan 9’s windowing system, dubbed 81/2, provides a virtual keyboard, mouse and screen to each of the applications running under it, while using a real keyboard, mouse and screen supplied by the operating system. So in addition to creating, deleting and arranging the windows themselves, its job is to be a server for certain resources used by its clients. It’s not icon-based, but windows are more than glass Teletypes, the company said, adding Plan 9 people tend to be text-oriented. It uses the 16-bit Unicode character set and X Window has been implemented. Plan 9 comes with libraries that can import Posix applications and emulate the Berkeley socket interface.
