VMS Help CC, /VAXC  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The CC command is used to invoke either the VAX C or Compaq C
  compiler.  If your system has a VAX C compiler already installed on
  it, the Compaq C installation procedure provides the option of
  specifying which compiler will be invoked by default when just the
  CC command verb is used.  To invoke the compiler that is not the
  default, use the CC command with the appropriate qualifier:
  CC/DECC for the Compaq C compiler, or CC/VAXC for the VAX C
  compiler.

  If your system does not already have a VAX C compiler installed on
  it, the CC command will invoke the Compaq C compiler.