Fonts & Encodings

A.5. The T_EX World

Appendix B of this book deals with the real and virtual metric data of T_EX and Ω. But T_EX long used bitmap fonts, compiled from font descriptions written in the METAFONT programming language (see Appendix F). In this section, we shall discuss the bitmap formats defined by Knuth and his students for the needs of T_EX.

A.5.1. The PXL and CHR Formats

Unlike humans, who learn languages as they grow up, METAFONT was born speaking several languages, which she later forgot. For instance, in 1983, METAFONT^[A-6] was able to produce fonts in FNT (nothing to do with the Windows FNT format; these were fonts for the Xerox Graphics Printer), VNT (for the Varian Versatec printer), ANT (Alphatype CRS), RST (Canon), OC (Dover), and WD (PrePress).

^[A-6] We are referring, of course, to METAFONT78, the ancestor of the current METAFONT, which was written in the proprietary language of the SAIL system. The interested reader can find all the SAIL files for the T_EX and METAFONT projects in [43].

It quickly became clear that it would be more practical to have a single bitmap format and to generate the data on the fly from this generic format, whether the task be on-screen display or printing. That became a reality in November 1981, when David Fuchs announced the PXL font format [145].

The PXL format (the abbreviation comes from the word pixel) is a variable-width bitmap format without compression: the glyphs are described by bitmap images, and at the end of the file there is a table ...