Register 15 contains a return code indicating
the success or failure of the request. Possible return codes (in decimal)
are:
0
The environment was activated and termination was requested.
4
Non-valid function code.
8
If token was initialized
by (init_main) or (init_sub), CEEPIPI(term) was called from a Language Environment-conforming
routine.
If token was initialized
by (init_main_dp), CEEPIPI(term) was called from a Language Environment-conforming
routine that is not running in a (main_dp) environment, or token is
already in use for another call to CEEPIPI