6.2.1 Language Concepts

The fundamental operation of the GNU troff formatter is the translation of the groff input language into a series of instructions concerned primarily with placing glyphs or geometric objects at specific positions on a rectangular page. In the following discussion, the term command always refers to this device-independent output language, and never to the language intended for direct use by document authors. Device-independent output commands comprise several categories: glyph output; font, color, and text size selection; motion of the drawing position; page advancement; drawing of geometric objects; and device control commands, a catch-all for other operations. The last includes directives to start and stop output, identify the intended output device, and embed URL hyperlinks in supported output formats.