FIELD has been a remarkably successful research project. The ideas first exhibited in the environment now form the basis for most of the current generation of programming environments, including Hewlett-Packard's Softbench, DEC's FUSE, Sun's Tooltalk, Lucid's Energize, and SGI's Codevision. FIELD pioneered the notion of broadcast messaging as a basis for tool integration. Moreover, many of the other tool concepts introduced in FIELD have made their way into these environments. Thus in discussing the FIELD environment, this book actually explains the inner workings of today's programming environments. The book will be valuable for those interested in the development of programming tools and environments, as well as serious users of programming environments. It will also be of interest to anyone undertaking a large software project, both by introducing the software tools needed to work on such a project and by demonstrating the concepts of message-based integration which can be applied to a variety of domains.