6.2 Device and Font Description Files

The groff font and output device description formats are slight extensions of those used by AT&T device-independent troff. In distinction to the AT&T implementation, groff lacks a binary format; all files are text files.¹²⁵ The device and font description files for a device name are stored in a devname directory. The device description file is called DESC, and, for each font supported by the device, a font description file is called f, where f is usually an abbreviation of a font’s name and/or style. For example, the ps (PostScript) device has groff font description files for Times roman (TR) and Zapf Chancery Medium italic (ZCMI), among many others, while the utf8 device (for terminal emulators) has only font descriptions for the roman, italic, bold, and bold-italic styles (R, I, B, and BI, respectively).

Device and font description files are read both by the formatter, GNU troff, and by output drivers. The programs delegate these files’ processing to an internal library, libgroff, ensuring their consistent interpretation.