VMS Help CC, Run-time functions, chdir  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Changes the default directory.

  Syntax:

       #include <unistd.h>

       int chdir(const char *dir_spec);  (POSIX-1)

       int chdir(const char *dir_spec, ...); (Compaq C Extension)

  where the ...  is an optional flag, available in all compilation
  modes except strict ANSI C mode (/STANDARD=ANSI89).  This flag is
  significant only when calling chdir from USER mode.  If the value
  of the flag is 1, the new directory is effective across images.  If
  the value is not 1, the original default directory is restored when
  the image exits.