Atari 400 Technical Reference Manual page 122

the same device or file, where it is illegal, lies with the
handler.
CLOSE
This vector table entry is called in response to a CLOSE command
to CIC. The handler is expected to release any held resources
that relate specifically to that device/filename, and for output
files to:
1) send any data remaining in handler buffers to the device,
2) mark the end of file
3) update any associated directories, allocation maps, etc.
At handler entry, the following parameters can be of interest:
x
=
index to originating IOCB.
Y
=
$92 (status
=
function not implemented by handler).
ICDNOZ [0021J
=
device number (1-4, for multiple device
handlers>.
ICAX1Z/ICAX2Z [002A/002BJ
=
device-specific information.
The handler attempts to perform the indicated CLOSE and
indicates the status of the operation by the value of the Y
register.
CIa releases the associated IOCB after the handler returns,
regardless of the operation status value.
GETBYTE
This vector table entry is called in response to a GET
CHARACTERS or GET RECORD command to CIO. The handler is
expected to return a single byte in the A register, or return an
error status in the Y register.
At handler entry, the following parameters can be of interest:
x
=
index to originating IOCB.
Y
=
$92 (status
=
function not implemented by handler).
ICDNOZ [0021J
=
device number (1-4, for multiple device handlers).
ICAX1Z/ICAX2Z [002A/002BJ
=
device-specific information.
The handler will obtain a data byte directly from the device or from a
handler-maintained buffer and return to
CIa
with the byte in the
A register and the operation status in the Y register.
OPERATING SYSTEM C016555 -- Section 9
137