Microsoft KB Archive/59131

= How to Just Trap CTRL, ALT, or SHIFT Keys in Basic =

Article ID: 59131

Article Last Modified on 8/16/2005

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APPLIES TO


 * Microsoft Visual Basic for MS-DOS
 * Microsoft QuickBasic 4.0
 * Microsoft QuickBASIC 4.0b
 * Microsoft QuickBasic 4.5 for MS-DOS
 * Microsoft BASIC Compiler 6.0
 * Microsoft BASIC Compiler 6.0b
 * Microsoft BASIC Professional Development System 7.0

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This article was previously published under Q59131



SUMMARY
Normally, to trap CTRL (CONTROL), ALT, and SHIFT in combination with other keys, you would set the bits for these keys in the first byte (keyboard flag) of the two CHR$ bytes in the KEY statement.

However, to trap the CTRL, ALT, and SHIFT keys alone (not in combination with other keys), the keyboard flag in the KEY statement should be CHR$(0) for the standard keyboard or CHR$(&H80) for keys specific to an extended keyboard.



MORE INFORMATION
The syntax of the KEY statement (where n=15 through 25 can be user-defined keys) is as follows:

KEY n, CHR$(keyboardflag) + CHR$(scancode)

The following table lists the scan codes for the CTRL, ALT and SHIFT keys:   Key           Scan Code ---          -   CTRL          &H1D ALT          &H38 LEFT SHIFT   &H2A RIGHT SHIFT  &H36 NOTE: To trap the RIGHT CTRL or RIGHT ALT key (found only on an extended 101 keyboard), the extended keyboard flag (&H80) must be used in the keyboard flag byte.

Code Example
The following code example traps the CTRL, ALT, and SHIFT keys alone: ' NOTE: This program requires NUM LOCK and CAPS LOCK to be off. KEY 15, CHR$(&H0) + CHR$(&H1D)    ' LEFT CTRL (on ON KEY(15) GOSUB Ctrl              ' Standard or Extended keyboard). KEY(15) ON

KEY 16, CHR$(&H80) + CHR$(&H1D)   ' RIGHT CTRL (on Extended keyboard). ON KEY(16) GOSUB Ctrl KEY(16) ON

KEY 17, CHR$(&H0) + CHR$(&H38)    ' LEFT ALT (on ON KEY(17) GOSUB alt               ' Standard or Extended keyboard). KEY(17) ON

KEY 18, CHR$(&H80) + CHR$(&H38)   ' RIGHT ALT (on Extended keyboard). ON KEY(18) GOSUB Alt KEY(18) ON

KEY 19, CHR$(&H0) + CHR$(&H2A)    ' LEFT SHIFT (on ON KEY(19) GOSUB Shift             ' Standard or Extended keyboard). KEY(19) ON

KEY 20, CHR$(&H0) + CHR$(&H36)    ' RIGHT SHIFT (on ON KEY(20) GOSUB Shift             ' Standard or Extended keyboard). KEY(20) ON

WHILE INKEY$ <> CHR$(27): WEND    ' Press ESC to end. END

Ctrl: PRINT &quot;CTRL&quot; RETURN

Alt: PRINT &quot;ALT&quot; RETURN

Shift: PRINT &quot;SHIFT&quot; RETURN

Additional query words: VBmsdos QuickBas BasicCom 1.00 4.00 4.00b 4.50 6.00 6.00b 7.00

Keywords: KB59131

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