1.TL 2Preface to the Third (2000) Edition 3.LP 4A great deal has happened to Plan 9 in the five years since its last release. 5Although much of the system will seem familiar, hardly any aspect 6of it is unchanged. 7The kernel has been heavily reworked; 8the graphical environment completely rewritten; 9many commands added, deleted, or replaced; 10and the libraries greatly expanded. 11Underneath, though, the same approach to computing remains: 12a distributed system that uses file-like naming to access and 13control resources both local and remote. 14.LP 15Some of the changes are sweeping: 16.IP 17Alef is gone, a casualty of the cost of maintaining multiple languages, compilers, 18and libraries in a diverse world, 19but its model for processes, tasks, and communication lives on 20in a new thread library for C. 21.IP 22Support for color displays is much more general, building on a new 23alpha-blending graphical operator called 24.CW draw 25that replaces the old 26.CW bitblt . 27Plan 9 screens are now, discreetly, colorful. 28.IP 29A new mechanism called plumbing connects applications together 30in a variety of ways, most obviously in the support of multimedia. 31.IP 32The interfaces to the panoply of rotating storage devices have been 33unified and extended, 34while providing better support for having Plan 9 coexist with other 35operating systems on a single disk. 36.IP 37Perhaps most important, this release of the system is being done under 38an open source agreement, providing cost-free source-level access to the 39software. 40.LP 41Plan 9 continues to be the work of many people. 42Besides those mentioned in the old preface, 43these people deserve particular note: 44Russ Cox did much of the work updating the graphics 45and creating the new disk and bootstrap model 46as well as providing a number of new commands; 47David Hogan ported Plan 9 to the Dec Alpha; 48and 49Sape Mullender wrote the new thread library. 50.LP 51Other new contributors include 52Bruce Ellis, 53Charles Forsyth, 54Eric Van Hensbergen, 55and 56Tad Hunt. 57.sp 58.in 3i 59Bell Labs 60.br 61Computing Science Research Center 62.br 63Murray Hill NJ 64.br 65June, 2000 66