The following conventions are used for names of macros, strings, and
registers. External names available to documents that use the
groff ms macros contain only uppercase letters and digits.
Internally the macros are divided into modules. The naming conventions are as follows.
*name.
@name.
:name; these are used only within the
par module.
!index.
Thus the groff ms macros reserve the following names.
*, @, and :.