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

  Functions consist of one or more blocks of statements that perform
  one logical operation.  They can be called from other functions
  either in the same program or in different programs.  A function
  may exchange values with the calling function by use of parameters.

  Function declarations have the following syntax:

       function_name()
  or
       function_name(arg1, arg2,...)
  or
       function_name(data-type arg1, data-type arg2,...)

  In the first form of the function declaration, the function takes
  no arguments.  In the second form, the function takes arguments;
  the arguments are declared outside the parameter list.  In the
  third form, the function declaration is a function prototype that
  specifies the type of its arguments in the identifier list; the
  prototype form is recommended.  In all three cases, the parenthesis
  after the function name are required.

  Compaq C for OpenVMS Systems provides a library of common
  functions.  These functions perform standard I/O operations,
  character and string handling, mathematical operations,
  miscellaneous system services, and UNIX* system emulation.  For
  more information, see HELP CC RUN-TIME_FUNCTIONS.

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 * UNIX is a trademark of The Open Group.