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(dvips.info)Glyph files

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Glyph files
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  Although a metric file (see the previous section) contains information
about the spatial and other properties of the character at position 75,
say, it contains nothing about what the character at position 75
actually looks like. The glyphs--the actual shapes of the letterforms
in a font--are defined by other files, which we call glyph files.  TeX
itself only reads the TFM file for a font; it does not need to know
character shapes.

  A "glyph file" is a file that defines the shapes of the characters in
a font.  The shapes can be defined either by outlines or by bitmaps.

  PostScript fonts are defined as "outline fonts": Each character in
the font is defined by giving the mathematical curves (lines, arcs, and
splines) that define its contours.  Different sizes of a character are
generated by linearly scaling a single shape. For example, a 10-point
`A' is simply half the size of a 20-point `A'.  Nowadays, outline fonts
usually also contain "hints"--additional information to improve the
appearance of the font at small sizes or low resolutions.

  Although various kinds of PostScript outline fonts exist, by far the
most common, and the only one we will consider, is called "Type 1".
The glyph files for Postscript Type 1 fonts typically have names ending
in `.pfa' ("printer font ASCII") or `.pfb' ("printer font binary").

  In contrast, glyph files for Computer Modern and the other standard
TeX fonts are "bitmap fonts", generated from Metafont (`.mf')
descriptions.  The Metafont program distributed with TeX generates
bitmaps from these descriptions.

  The glyph files for TeX bitmap fonts are usually stored in "packed
font" (PK) files.  The names of these files end in `.NNNpk', where NNN
is the resolution of the font in dots per inch.  For example,
`cmr10.600pk' contains the bitmaps for the `cmr10' font at a resolution
of 600dpi.  (On DOS filesystems, it's more likely `dpi600\cmr10.pk'.)

  Metafont actually outputs "generic font" (GF) files, e.g.,
`cmr10.600gf', but the GF files are usually converted immediately to PK
format (using the `gftopk' utility that comes with TeX) since PK files
are smaller and contain the same information. (The GF format is a
historical artifact.)