Chapter 1. Introduction

In September 1987, the Massachusetts Institute of Technology released the first snapshot of what may well become one of the most significant software technologies of the 1990s: Version 11 of the X Window System, commonly referred to as X11. X11 may not change the world, but it is likely to change the world of workstations.

The X Window System is being adopted as a standard by nearly every workstation manufacturer and should eventually replace or be supported under their proprietary windowing systems. Versions will also be available for personal computers and supercomputers.

For the first time, portable applications can be written for an entire class of machines rather than for a single manufacturer’s equipment. Programmers can write in a single graphics language and expect their applications to work without significant modifications on dozens of different computers.

What’s more, since X is a network-based windowing system, applications can run in a network of systems from different vendors. Programs can be run on a remote computer, and the results displayed on a local workstation. Proprietary networks have been around for a while. However, network cooperation of different computers has been held up by the lack of a common applications language. Now there is one.

Vendors hope that X will lead to a software explosion similar to the one that occurred in response to the PC standard on microcomputers.

1.1 Versions of X

X was developed jointly by MIT’s Project Athena and Digital Equipment Corporation, with contributions from many other companies. It was masterminded by Robert Scheifler and colleagues at MIT, though it owes some debt to the “W” windowing package developed by Paul Asente at Stanford.

There have been numerous research versions of X. Version 10, Release 4 (popularly known as X10.4), which was released in 1986, became the basis for several commercial products. Development of most X10.4 products was curtailed, however, when it became apparent that Version 11 would not be compatible with it. Version 11, Release 1 became available in September 1987, Release 2 in March 1988, Release 3 in February 1989, Release 4 in January 1990, and Release 5 in August 1991.

Version 11 is a complete window programming package. It offers much more flexibility in the areas of supported display features, window manager styles, and support for multiple screens and provides better performance than X Version 10. It is fully extensible. But just as important, the X11 subroutine library (Xlib) is expected to be stable for several years and to be at least a de facto industry standard. That means that programs written with this library will not need major revisions because of software updates. While there may be additions to this library, there will not be incompatible changes to it.

With X11 Release 2, control of X passed from MIT to the X Consortium, an association of major computer manufacturers who plan to support the X standard. The Consortium was formed in January 1988 and includes virtually all large computer manufacturers. Many software houses and universities are associate members, who also have a voice in controlling the standard and receive advance access to newly released software.

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