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Setting Traps for Events and Errors
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Statements and Functions Used for Setting Traps for Events and Errors
Statement or
Task function Action
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Trapping errors ON ERROR Enables an error-handling routine
while a program and specifies the location of
is running that routine in the program. Also
used to disable an error-handling
routine.
RESUME Returns control to the program
after executing an error-handling
routine.
Getting ERR Returns the code for an error
error-status that occurred at run time.
data
ERL Returns the number of the line
on which an error occurred
(useful only if program has line
numbers).
ERDEV Returns a device-specific error
code for the last device (such
as a printer) for which the
operating system detected an
error.
ERDEV$ Returns the name of the last
device for which the operating
system detected an error.
Defining your ERROR Simulates the occurrence of
own error a BASIC error with a specified
codes error code; can also be used to
define an error not trapped by BASIC.
Trapping events ON event Specifies a routine to branch to
while a program is running and an
event occurs. An event can occur
when characters are received at a
communications port, a key is
pressed, a lightpen is activated,
an OS/2 protected mode signal is
received, a joystick trigger is
pressed, a specified time has
elapsed, or a user-defined event
has occurred.
event ON Enables trapping of the given
event.
event OFF Disables trapping of the given
event.
event STOP Suspends trapping of the given
event.
RETURN Returns control to the program
after executing an event-handling
subroutine.
EVENT Enable or disable trapping of
events. EVENT OFF and ON are
used to bracket sections of code
where events do not need to be
detected and trapped.