This book is for programmers who are familiar with Release 5 of the X Window System and who want to know how to use the new features of Release 6. Intended as an update for owners of Volumes 1, 2, 4, and 5 of the O'Reilly & Associates X Window System series, it provides complete tutorial and reference information for all new Xlib and Xt functions. The book includes an overview of the R6 changes as they affect application programming; preparing applications for Session Management; new Xt features including signal handling and C[superscript ++] support; creating multi-threaded X applications; using transformed (rotated, scaled, or obliqued) fonts; internationalizing X applications; an introduction to the X Image extension; and reference pages for all new Xlib and Xt functions. Together with Volumes 2 and 5, owners of the Programmer's Supplement for Release 6 of the X Window System have a complete set of reference pages for the current X Consortium standards for Xlib and Xt.