dir_spec

    A null-terminated character string naming a directory in either
    an OpenVMS or UNIX style specification.

  . . .

    This argument is an VSI C extension available when not
    defining any of the standards-related feature-test macros and not
    compiling in strict ANSI C mode (/STANDARD=ANSI89). The argument
    is an optional flag of type int that 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.