How to Trap CTRL+UP and CTRL+DOWN Arrow Key Sequences

SUMMARY

This article gives an example showing how to capture the key sequences of the CTRL key with the UP and DOWN arrow keys. It involves defining new keys that are equivalent to the key sequence and then trapping them. The CTRL key is defined by the constant &H4, the UP arrow key by 72, and the DOWN arrow key by 80.

Please note that you must make separate user-defined KEY statements for trapping CTRL+UP and CTRL+DOWN in combination with the SHIFT, ALT, NUM LOCK, and CAPS LOCK keys. The keyboard flags for these other keystroke combinations must be added together to define a given keystroke sequence.

     CONST CTRLFLAG = &H4     'define constants
   CONST UPARROW = 72
   CONST DOWNARROW = 80

'Setup keys to trap, and turn on the trapping
   KEY 15, CHR$(CTRLFLAG) + CHR$(UPARROW)
   KEY 16, CHR$(CTRLFLAG) + CHR$(DOWNARROW)
   ON KEY(15) GOSUB GotUp
   ON KEY(16) GOSUB GotDown
   KEY(15) ON
   KEY(16) ON

   WHILE INKEY$ <> "Q"     'sit in loop and wait for keypresses
   WEND
   END

GotUp:
   PRINT "Ctrl-Up"
   RETURN

GotDown:
   PRINT "Ctrl-Down"
   RETURN