A user written procedure must
be provided to define how the program should act upon receiving
a subsystem break.
A call to XCONTRAP must be included in the program,
specifying the external address of the procedure written in Step
1 as the value of plabel. This arms the [CTRL]Y
trap.
A call to FCONTROL(17) must be included in the program
to enable the subsystem break function.
If the subsystem break character is received during
execution of the program, the procedure specified in the call to
XCONTRAP is executed.
A call to RESETCONTROL must be executed when the
program is ready to receive another subsystem break.
A new subsystem break character may be defined through
FCONTROL(41), if the terminal is placed in transparent mode, or
through FDEVICECONTROL.
You can redefine your trap handling procedure at
any point during execution of the program through another call to
XCONTRAP.
If desirable at any time, FCONTROL(16) may be called
to disable subsystem break. A call to FCONTROL(17) enables it again.
