1.3 GNU troff Capabilities

GNU troff is a typesetting document formatting program; it provides a wide range of low-level text and page operations within the framework of a programming language. These operations compose to generate footnotes, tables of contents, mathematical equations, diagrams, multi-column text, and other elements of typeset works. Here is a survey of formatter features; all are under precise user control.

• text filling, breaking, alignment to the left or right margin; centering
• adjustment of inter-word space size to justify text, and of inter-sentence space size to suit local style conventions
• automatic and manual determination of hyphenation points
• pagination
• selection of any font available to the output device
• adjustment of type size and vertical spacing (or “leading”)
• configuration of line length and indentation amounts; columnation
• drawing of geometric primitives (lines, arcs, polygons, circles, …)
• setup of stroke and fill colors (where supported by the output device)
• embedding of hyperlinks, images, document metadata, and other inclusions (where supported by the output device)

roff as a programming language also supports evaluation of arithmetic expressions, storage and retrieval of parameters (“registers” and “strings”), and altered flow of control dependent on the foregoing.