troff (/ˈtiːrɒf/), short for "typesetter roff", is the major component of a document processing system developed by AT&T Corporation 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.