The UNIX* operating system provides programs for sophisticated docu ment preparation within the framework of a general-purpose operating system. The document preparation software includes a text editor, pro grammable text formatters, macro-definition packages for a variety of page layout styles, special processors for mathematical expressions and for tabular material, and numerous supporting programs, such as a spelling-mistake detector. In practice, this collection of facilities has pro ven to be easy to learn and use, even by secretaries, typists, and other nonspecialists.Experiments have shown that preparation of complicated documents is about twice as fast as on other systems. There are many benefits to using a general-purpose operating system instead of specialized stand-alone terminals or a system dedicated to "word processing. " On the UNIX system, these include an excellent software development facility and the ability to share computing and data resources among a community of users.