Article ID: 161304 - View products that this article applies to.
This article was previously published under Q161304
Microsoft Visual Basic has a Hex$() function to convert a number into a string of Hexadecimal digits. However, it has no obvious function to perform the inverse conversion. This article details how to use the Val() function to perform the Hexadecimal to Long Integer conversion, plus a trap to avoid.
The Val() function can be used to convert a string of decimal digits into a number. It can also be used on a string of hexadecimal digits, but you have to append the characters "&H" to the string of digits so that the Val() function will use the correct number base in the conversion process.
Integer TrapIf you are assigning the results of the conversion to a Long integer variable, you will probably only want numbers in the range 80000000 to FFFFFFFF to be treated as negative numbers. However, without taking special precautions, numbers in the range 8000 to FFFF will also be treated as negative.
This occurs because numbers with four or fewer digits are converted to signed 2-byte integers. When the signed integer intermediate value is converted to a Long (or 4-byte) integer, the sign is propagated.
Visual Basic 4.0/Access 95 and LaterBy appending the "&" Long suffix to the hexadecimal string, even small numbers are treated as Long. The following function performs the conversion correctly:
Visual Basic 3.0/Access 2.0 and EarlierThe method illustrated above will not work in Microsoft Visual Basic 3.0 or earlier for hexadecimal numbers greater or equal to 80000000. Please see the REFERENCES section of this article for more information.
Because this problem does not occur with numbers that fall in the Integer Trap range, the alternate function given below adds error trapping to try again without the appended "&" Long suffix:
Usage of either version of the function is as follows:
Microsoft Visual Basic Help topic: Val Function
Microsoft Visual Basic 4.0 ReadMe topic: Coercion of Hexadecimal Values
For more information, please see the following article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/95431/EN-US/ )FIX: Type Mismatch Error If Use VAL Function on Big Value
Article ID: 161304 - Last Review: July 13, 2004 - Revision: 3.2