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Practical Visual BasicMath
Applies to  VB4+ 

Working with Unsigned Integers

Code

The UIntToLong function treats an Integer as if it were unsigned and converts it to a Long, resulting in a number between 0 and 65535 (&HFFFF&):

UIntToLong preserves the bits of the integer that's passed to it. For example, UIntToLong(&H1234) = &H1234& and UIntToLong(&HFEDC) = &HFEDC&. (Note that &HFEDC equals -292 while &HFEDC& equals 65244.)

The LongToUInt function does the opposite, converting a Long between 0 and 65535 to an Integer with the same bits:

For example, LongToUInt(&H1234&) = &H1234 and LongToUInt(&HFEDC&) = &HFEDC.

Example

The GIF file format uses two unsigned integer fields to store the width and height of an image. The following procedure reads a GIF file and displays the size of the image:

' Outputs the size of a GIF image to the Immediate window.
Public Sub DisplayGIFImageSize(FileName As String)
    Dim FileNum As Integer, Width As Integer, Height As Integer
    FileNum = FreeFile
    
    Open FileName For Binary Access Read Lock Write As FileNum
    Get #FileNum, 7, Width
    Get #FileNum, 9, Height
    Close FileNum
    
    Debug.Print "Width = " & UIntToLong(Width)
    Debug.Print "Height = " & UIntToLong(Height)
End Sub
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