20.4.1 OpenVMS Run-Time Library Routines
  The OpenVMS Run-Time Library routines are grouped ac-
  cording to the types of tasks they perform. The routines
  in each group have a prefix that identifies them as mem-
  bers of a particular OpenVMS Run-Time Library facility.
  Table 20-2 lists all the language-independent Run-Time
  Library facility prefixes and the types of tasks each facility
  performs.