Specifications

Chapter 14. Statement Reference
238
Syntax:
KEY (keynumber){ON|OFF}
Parameter:
keynumber
A numeric expression which returns a value from 1 to 31, 33 to 38, and 501
to 550.
Description:
■ KEY ON
KEY
ON enables keystroke trapping for a function key specified by keynumber.
(Refer to Appendix E, "Key Number Assignment on the Keyboard.")
• Between every execution of statements, the Interpreter checks whether a function
key specified by the
KEY ON statement is pressed or not. If the key is pressed,
the Interpreter transfers control to the event-handling routine defined by an ON
KEY...GOSUB
statement (which should be executed before the KEY ON state-
ment).
• If a function key which has been assigned a null string by the KEY statement is
specified by the KEY ON statement, the keystroke trap takes place.
• If you specify a function key which has been defined as a backlight function on/off
key, trigger switch, shift key, or software keyboard display key by using the KEY
ON
statement, then no keystroke trap takes place.
• Keystroke trapping has priority over the INKEY$ function.
• When a program waits for the keyboard entry by the INPUT, LINE INPUT state-
ment or
INPUT$ function, pressing a function key specified by the KEY ON state-
ment neither reads the pressed key data nor causes keystroke trapping.
• Specifying 32 to
keynumber will be ignored.
■
KEY OFF
KEY
OFF disables keystroke trapping for a function key specified by keynumber.
• Specifying 32 to keynumber will be ignored.
I/O statement
KEY ON and KEY OFF
Enables or disables keystroke trapping for a specified function key.