Special fonts are those that GNU troff searches, in mounting
position order, when it cannot find a requested glyph in the selected
font. Typically, special fonts contain unstyled glyphs and are declared
as such in their description files; see Font Description File Format. The “Symbol” and “Zapf Dingbats” fonts of the PostScript
and PDF standards are examples. Ordinarily, only typesetters have
special fonts.
GNU troff’s special and fspecial requests permit
a document to supplement the set of fonts searched for glyphs.
See Using Symbols.
.special [s1 s2 …] ¶.fspecial f [s1 s2 …] ¶special designates each font sn as special. Initially,
this list is empty.
fspecial designates each font as special only when
font f is selected. Initially, this list is empty.
Invoking special or fspecial again overwrites the previous
list; without arguments, the relevant list is made empty. Special fonts
are searched in the order they appear as arguments. Each font sn
is mounted, and not automatically unmounted if superseded by a
subsequent special or fspecial request.