Another example listed below demonstrates how to programmatically (without pressing the key) force the CAPS LOCK state to ON or OFF. This same example can be used for the NUM LOCK and SCROLL LOCK keys.
KEY n, CHR$(keyboardflag) + CHR$(scancode)
By defining traps for NUM LOCK and CAPS LOCK, your program can effectively reduce (by a factor of four) the number of keys needed to be defined. For example, to trap both the CTRL+ALT+DEL and CTRL+BREAK keystroke combinations, 16 keys must be created to handle all the different keystroke combinations. This is more than the maximum number of user-defined keys (11). By defining CAPS and NUM LOCK traps, only 4 additional keys must be defined.
Key Scan Code
CAPS LOCK &H3A
NUM LOCK &H45
SCROLL LOCK &H46
Code ExampleThe following code example disables the toggles for the CAPS LOCK, NUM LOCK, and SCROLL LOCK keys:
' NOTE: This program assumes NUM LOCK and CAPS LOCK are off at the
' beginning. See the article referenced above for how to set
' the NUM and CAPS LOCK off.
KEY 15, CHR$(&H0) + CHR$(&H3A) ' CAPS LOCK
ON KEY(15) GOSUB caps
KEY 16, CHR$(&H0) + CHR$(&H45) ' NUM LOCK
ON KEY(16) GOSUB num
KEY 17, CHR$(&H0) + CHR$(&H46) ' SCROLL LOCK
ON KEY(17) GOSUB scroll
WHILE INKEY$ <> CHR$(27): WEND
caps: PRINT "NO CAPS LOCK TOGGLE!"
num: PRINT "NO NUM LOCK TOGGLE!"
scroll: PRINT "NO SCROLL LOCK TOGGLE!"
DEF SEG = 0
X = PEEK(1047) AND 64
To force the CAPS LOCK off, use the following command:
DEF SEG = 0
POKE 1047, PEEK(1047) AND 191
DEF SEG = 0
POKE 1047, PEEK(1047) OR 64
Although the INS key is included in the table shown above, you cannot make use of it. In Visual Basic for MS-DOS, you cannot use either the POKE or the CALL INTERRUPT to set the Insert mode when you are in Forms mode. The only way to set the Insert mode is by pressing the INS key. This is by design in Visual Basic for MS-DOS.
Bit No. Decimal Value Keyboard Flag
0 1 RIGHT SHIFT
1 2 LEFT SHIFT
2 4 CTRL (Control)
3 8 ALT
4 16 SCROLL LOCK
5 32 NUM LOCK
6 64 CAPS LOCK
7 128 INS (Insert mode)
To determine the state of any flag, the following statement will return "0" if the flag is clear (off or not pressed), and will return <bval> if the flag is set (on or pressed):
To force the flag on (this applies only to the LOCK keys -- not the INS key), you need to set the appropriate bit. You can do this with the following POKE statement:
PEEK(1047) AND <bval>
(where <bval> is the decimal value of the bit that represents
the flag you want)
To force the flag off, you can use the following similar statement:
POKE 1047, PEEK(1047) OR <bval>
(where <bval> is the decimal value of the flag you want to set)
Note that simply poking the bit value into 1047 would effectively set the flag, but would also clear all other flags. Thus, be sure to retain the previous values of the other flags by using the above strategies.
POKE 1047, PEEK(1047) AND (255 - <bval>)
Note that instead of using PEEK, you may also get the status of keyboard flags with IBM ROM BIOS Interrupt 16h, using function number 2. This interrupt returns the ROM BIOS flags byte that describes the state of the following keyboard toggles and SHIFT keys: RIGHT SHIFT or LEFT SHIFT key down, CTRL key down, ALT key down, SCROLL LOCK on, NUM LOCK on, CAPS LOCK on, INSert on.
Article ID: 59132 - Last Review: Aug 16, 2005 - Revision: 1