.TL PREFACE TO VOLUME 2 .LP This selection of supporting papers to accompany Volume 1 of the Tenth Edition .UX Programmer's Manual reflects both continuity and change during the decade since the Seventh Edition when the last such collection appeared. Thirty out of forty papers are completely new, and many of the rest have been substantially rewritten. With few exceptions the papers represent the work of members of the center where .UX was born, Computing Science Research at AT&T Bell Laboratories. The earlier work of this center has become so widely known that many of the more basic papers from the Seventh Edition could safely be dropped to make way for more recent work. .PP Some papers continue important themes that date from the early days of the system: tools for programming and tools for document preparation. Some address the down-to-earth subject of the care, feeding, and protection of a multifaceted system in an imperfect world. Others address topics in the increasingly pervasive theme of communications and distributed computing: readily distributable `stream' input/output, cross-machine file systems, the use of intelligent multiplexed terminals, simple worldwide electronic mail. A few papers suggest the breadth of research applications that meet and reinforce each other in this system: music, program verification, image processing, and graphics. .PP Here one can find more up-to-date information about the popular .I troff family of typesetting software than in any other published work. One may also see, in the diverse styles of the several authors, various ways to exploit .I troff and some of its newer rivals. The entire volume is brought together in a .I "tour de force of text processing, the index, which Lorinda Cherry gathered by largely automatic means from a highly disparate electronic corpus. .sp 2 .in 4i A. G. Hume .br M. D. McIlroy .br January, 1990 .in 0