QBasic 1.1: ON KEY Statement
Explanation
KEY, ON KEY Statements (Event Trapping)
KEY enables, disables, or suspends event trapping of a key.
If event trapping is enabled, ON KEY branches to a subroutine whenever the key is pressed.
Worth knowing
Useful and cross-version information about the programming environments of QBasic, QuickBasic and Visual Basic for DOS.
Syntax
| KEY(n%) ON |
| KEY(n%) OFF |
| KEY(n%) STOP |
| ON KEY(n%) GOSUB line |
Description / Parameter(s)
| n% |
A value that specifies a function key, direction key, or user-defined key: |
| |
| n% |
Key |
| 0 |
All keys listed here (KEY(0) ON, KEY(0) OFF, and KEY(0) STOP only). |
| 1-10 |
Function keys F1-F10. |
| 11 |
Up Arrow key. |
| 12 |
Left Arrow key. |
| 13 |
Right Arrow key. |
| 14 |
Down Arrow key. |
| 15-25 |
User-defined keys. For more information, see Declaring User-Defined Keys. |
| 30, 31 |
Function keys F11 and F12. |
|
| KEY(n%) ON |
Enables event trapping for the specified key. |
| KEY(n%) OFF |
Disables key event trapping. |
| KEY(n%) STOP |
Suspends key event trapping. Events are processed once event trapping is enabled by KEY ON. |
| line |
The label or number of the first line of the event-trapping subroutine. |
Example
'This example requires Caps Lock and Num Lock to be off.
CONST ESC = 27
KEY 15, CHR$(&H4) + CHR$(&H1F) 'Set up Ctrl+S as KEY 15.
ON KEY(15) GOSUB PauseHandler
KEY(15) ON
WHILE INKEY$ <> CHR$(ESC)
PRINT "Press Esc to stop, Ctrl+S to pause."
PRINT
WEND
END
PauseHandler:
SLEEP 1
RETURN