||X register - address of name string.
||A register - device number.
B register - vector number.
|| This service will call the LANGUAGE
vector of all devices in memory and pass them the value in the X register.
If a device signals that it is prepared to handle the procedure whose name
is pointed to by the X register then the service will return with the A
register containing the device number and the B register containing the
vector number of the code to handle the procedure.
To determine the device number and vector number of the RS232 service
which is prepared to handle the LINPUT$ procedure the following code
fragment can be used.
LDX #LINPUT_NAME ; POINT TO LINPUT$
OS DV$LKUP ; SEARCH FOR RS232 DEVICE
BCS ERROR ; UNABLE TO HANDLE LINPUT$
STD LVECT ; SAVE A&B FOR LATER USE
RTS ; WITH DV$VECT
LVECT: DW 0
||230 - device not present.