To initiate and terminate key capture in a GW-BASIC program.
KEY(n) `ON
KEY(n) OFF
KEY(n) STOP
n is a number that indicates which key is to be captured. Keys are numbered as follows:
| Key Number | Key |
|---|---|
| 1-10 | Function keys F1 through F10 |
| 11 | CURSOR UP |
| 12 | CURSOR LEFT |
| 13 | CURSOR RIGHT |
| 14 | CURSOR DOWN |
| 15-25 | Keys defined in the following format (see KEY statement): KEY n, CHR$(hex_code) + CHR$(scan_code) |
| 30 and 31 | Function keys F11 and F12 |
Execution of the KEY(n) ON statement is required to activate keystroke capture from the function keys or cursor control keys. When the KEY(n) ON statement is activated and enabled, BASIC checks each new statement to see if the specified key is pressed. If so, BASIC performs a GOSUB to the line number specified in the ON KEY(n) statement. An ON KEY(n) statement must precede a KEY(n) statement.
When KEY(n) OFF is executed, no key capture occurs and no keystrokes are retained.
If KEY(n) STOP is executed, no key capture occurs, but if a specified key is pressed, the keystroke is retained so that immediate keystroke capture occurs when a KEY(n) ON is executed.
For further information on key trapping, see the ON KEY(n) statement.
ON KEY(10) GOSUB Handler
KEY(10) ON
PRINT "Press F10 to stop"
FOR i = TO 100000
PRINT i
NEXT i
Handler:
STOP