HOWTO: Use an Ampersand (&) to Suppress Sign Extension

• Microsoft Visual Basic Control Creation, Learning, Professional, and Enterprise Editions for Windows, version 5.0
• Microsoft Visual Basic Standard, Professional, and Enterprise Editions, 16-bit and 32-bit, for Windows, version 4.0

SUMMARY

Adding an ampersand (&) character to the end of a Hexadecimal number will ensure that it is not sign extended. This can be useful when an unsigned constant must be passed to a routine and the magnitude of the constant is greater than or equal to 32,768 (&H8000 in Hexadecimal). If the ampersand is not placed on the end of the constants, Visual Basic assumes that the numbers are sign extended.

MORE INFORMATION

The following example illustrates the effect of an ampersand on a Hexadecimal constant:

1. Start a new project in Visual Basic. In the default form (Form1), place the following code in the Click event for the form:

   
         Private Sub Form_Click()
            Dim j As Long
            j = &H8000
            Debug.Print j
            j = &H8000&
            Debug.Print j
         End Sub 




2. Run the code by pressing the F5 key. The Debug window shows the output as -32,768 followed by 32,768 indicating that the ampersand does suppress the sign.

Additional query words:

Keywords : kbprg kbVBp400 kbVBp500 kbhowto VB4WIN VBKBProgramming VBKBVBA
Version : WINDOWS:4.0,5.0
Platform : WINDOWS
Issue type : kbhowto