| .Selected Event and Error Trapping Example Programs. |
|
 Selected Programs Trapping Programs Contents Index |
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| Event and Error Trapping |
| |
| The following program shows how to trap an event that occurs while a |
| program is running. With event trapping, you can get your program to |
| detect run-time events such as keystrokes. |
| |
| Example 1 - Event Trapping |
| |
| If you use a 101-key keyboard, you can trap any of the keys on the |
| dedicated keypad by assigning the string |
| |
| CHR$(128) + CHR$(scancode) |
| |
| to any of the keynumber values from 15 to 25. |
| |
| The next example shows how to trap the LEFT direction keys on both |
| the dedicated cursor keypad and the numeric keypad. |
| |
| ' 128 = keyboard flag for keys on the |
| ' dedicated cursor keypad |
| ' 75 = scan code for LEFT arrow key |
| ' |
| KEY 15, CHR$(128) + CHR$(75) ' Trap LEFT key on |
| ON KEY(15) GOSUB CursorPad ' the dedicated |
| KEY(15) ON ' cursor keypad. |
| |
| ON KEY(12) GOSUB NumericPad ' Trap LEFT key on |
| KEY(12) ON ' the numeric keypad. |
| |
| DO |
| LOOP UNTIL INKEY$ = "q" ' Idle loop |
| END |
| |
| CursorPad: |
| PRINT "Pressed LEFT key on cursor keypad." |
| RETURN |
| |
| NumericPad: |
| PRINT "Pressed LEFT key on numeric keypad." |
| RETURN |
