SIGNAL Statements
 ----------------------------------------------------------------------------


 Action

 Enable, disable, or suspend event trapping for an OS-2 protected-mode
 signal.


 Syntax



  SIGNAL( n%)  ON


  SIGNAL( n%)  OFF


  SIGNAL( n%)  STOP

 Remarks


 The argument  n% identifies an OS-2 protected-mode signal. The following
 table lists the numbers of the protected-mode signals.

-----------------------------------------------------------------------------
 Number                Signal
 ----------------------------------------------------------------------------
 1                     Ctrl+C
 2                     Pipe connection broken
 3                     Program terminated
 4                     Ctrl+Break
 5                     Process flag A
 6                     Process flag B
 7                     Process flag C






  SIGNAL( n%)  OFF disables trapping of OS-2 signal  n%. No trapping takes
 place until another  SIGNAL( n%)  ON statement is executed. Events occurring
 while trapping is off are ignored.

  SIGNAL( n%)  STOP suspends trapping of OS-2 signal  n%. No trapping takes
 place until a  SIGNAL( n%)  ON statement is executed. Events occurring while
 trapping is suspended are remembered and processed when the next  SIGNAL(
 n%)  ON statement is executed. However, remembered events are lost if
 SIGNAL( n%)  OFF is executed.

 When a signal-event trap occurs (that is, the  GOSUB is performed), an
 automatic  SIGNAL STOP is executed so that recursive traps cannot take
 place. The  RETURN operation from the trapping routine automatically
 performs a  SIGNAL ON statement unless an explicit  SIGNAL OFF was performed
 inside the routine. For more information, see Chapter 9, "Event Handling" in
 the  Programmer's Guide.


 Note

 The  SIGNAL statement is available only for OS-2 protected mode.


 See Also

  ON  event


 Example


 The following example uses  ON SIGNAL to trap an event in the OS-2 operating
 system.

 PRINT "This program traps Ctrl+Break. Press Q to quit."


 EVENT ON





 ' Set up the signal-event trap and enable.


 ON SIGNAL(4) GOSUB CtrlBreak


 SIGNAL(4) ON





 ' Wait until the signal event occurs.


 DO . LOOP UNTIL UCASE$(INKEY$) = "Q"


 PRINT "'Q' pressed - Program terminating normally."


 END





 CtrlBreak.


     PRINT "A SIGNAL(4) event occurred."


     PRINT "Press 'Q' to quit."


     RETURN