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The COM statements enable, disable, or suspend event trapping at the COM
port.
 
COM(n%) ON
COM(n%) OFF
COM(n%) STOP
 
Usage Notes
    ■ COM(n%) ON enables communications-event trapping at COM port n%. If a
      character arrives at a communications port after a COM(n%) ON
      statement, the routine specified in the ON COM statement is
      executed.
    ■ COM(n%) OFF disables communications-event trapping at COM port n%. No
      trapping takes place until another COM(n%) ON statement is executed.
      Events occurring while trapping is off are ignored.
    ■ COM(n%) STOP suspends communications-event trapping at COM port n%. No
      trapping takes place until a COM(n%) ON statement is executed. Events
      occurring while trapping is suspended are remembered and processed
      when the next COM(n%) ON statement is executed. However, remembered
      events are lost if a COM(n%) OFF statement is executed.
    ■ When a signal-event trap occurs (that is, the GOSUB is performed),
      an automatic COM(n%) STOP is executed so that recursive traps cannot
      take place. The RETURN from the trapping routine automatically executes
      a COM(n%) ON statement unless an explicit COM(n%) OFF was performed
      inside the routine.
    ■ If your program contains event-handling statements and you are
      compiling from the BC command line, use the BC /W or /V option.
      (The /W option checks for events at every label or line number; the
      /V option checks at every statement.) If you do not use these
      options and your program contains event traps, BASIC generates the
      error message, "ON event without /V or /W on command line."
    ■ For more information, see Chapter 9, "Event Handling" in the
      Programmer's Guide.