Commodore Plus 4 - Page 323

The Operating System 311
$02 = The specified logical file is already open.
$04 = The specified file name is not found on the specified device.
$05 = The specified device is not present.
The system 1/ O status byte may also be checked for errors. It is read using
READSS ($FFB7).
$FFC3 CLOSE
Registers Altered: .A, .X
This routine is vectored through $031 A-$031B. This routine closes the logical
file specified by the value in .A.
The system I/O status byte may be checked for errors. It is read using
READSS ($FFB7).
SFFC6 CHKIN
Registers Altered: .A, .X
This routine is vectored through $031 C-$031D. The logical file specified by the
value of .X, which must have been previously opened using OPEN ($FFC0), is
designated as an input channel.
If an error occurs, the message flag (see SETMSG, $FF90) is consulted to
determine what message (if any) to output. The carry is returned set, and .A
contains the error number. The possible errors are as follows:
$03 = The specified logical file is not open.
$05 = The specified device is not present.
$06 = The specified device is not an input device.
The system I/O status byte may also be checked for errors. It is read using
READSS ($FFB7).
SFFC9 CHOUT
Registers Altered: .A, .X
This routine is vectored through $031 E-$031F. The logical file specified by the
value of .X, which must have been previously opened using OPEN ($FFC0), is
designated as an output channel.
If an error occurs, the message flag (see SETMSG, $FF90) is consulted to
determine what message (if any) to output. The carry is returned set, and .A
contains the error number. The possible errors are as follows: