troff (), short for "typesetter roff", is the major component of a document processing system developed by Bell Labs for the Unix operating system. troff and the related nroff were both developed from the original roff. While nroff was intended to produce output on terminals and line printers, troff was intended to produce output on typesetting systems, specifically the Graphic Systems CAT that had been introduced in 1972. Both used the same underlying markup language and a single source file could normally be used by nroff or troff without change. troff features commands to designate fonts, spacing, paragraphs, margins, footnotes and more. Unlike many other text formatters, troff can position characters arbitrarily on a page, even overlapping them, and has a fully programmable input language. Separate preprocessors are used for more convenient production of tables, diagrams, and mathematics. Inputs to troff are plain text files that can be created by any text editor. Extensive macro packages have been created for various document styles. A typical distribution of troff includes the me macros for formatting research papers, man and mdoc macros for creating Unix man pages, mv macros for creating mountable transparencies, and the ms and mm macros for letters, books, technical memoranda, and reports. History troffs origins can be traced to a text-formatting program called RUNOFF, which was written by Jerome H. Saltzer for MIT's CTSS operating system in the mid-1960s. (The name allegedly came from the phrase I'll run off a document.) Bob Morris ported it to the GE 635 architecture and called the program roff (an abbreviation of runoff). It was rewritten as rf for the PDP-7, and at the same time (1969), Doug McIlroy rewrote an extended and simplified version of roff in the BCPL programming language. The first version of Unix was developed on a PDP-7 which was sitting around Bell Labs. In 1971 the developers wanted to get a PDP-11 for further work on the operating system. In order to justify the cost for this system, they proposed that they would implement a document-formatting system for the Bell Labs patents department. This first formatting program was a reimplementation of McIllroy's roff, written by Joe F. Ossanna. When they needed a more flexible language, a new version of roff called nroff (newer "roff") was written, which provided the basis for all future versions. When they got a Graphic Systems CAT phototypesetter, Ossanna modified nroff to support