VMS Help PASCAL, Predeclared Routines, Null String, C_STR  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The C_STR function takes a compile-time  string  expression  and
  returns  a  C_STR_T  pointer  to  a static string literal with a
  terminating null character.

  Syntax:

     C_STR(e)

  The C_STR function can also accept a Pascal variable  of  either
  PACKED ARRAY OF CHAR, VARYING OF CHAR, or STRING.

  Syntax:

     C_STR(v)

  In this form, it will return a C_STR_T value that represents the
  first  character  in  the string variable.  It does not ensure a
  terminating  null  byte.   The  programmer   must   handle   the
  null-termination   to  treat  a  Pascal  string  variable  as  a
  null-terminated string.