Microsoft KB Archive/213706

= XL2000: How to Use the Imp Operator for Binary Comparison =

Article ID: 213706

Article Last Modified on 11/23/2006

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APPLIES TO


 * Microsoft Excel 2000 Standard Edition

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This article was previously published under Q213706





SUMMARY
The Microsoft Visual Basic for Applications Imp operator is used to perform a logical implication on two expressions. If you are using the Imp operator with two numeric expressions as arguments, Microsoft Excel performs a bit-wise comparison of identically positioned bits.



MORE INFORMATION
The syntax for the Imp operator is as follows

=  Imp

where  and   are any expressions and   is any numeric variable.

When you use the Imp operator to perform a bit-wise comparison of identically positioned bits in two numeric expressions, the result of the bit-wise comparison is determined using the rules in the following table.   Bit in Expression1   Bit in Expression2   Bit in Result ---          1                     1                 1           1                     0                 0           0                     1                 1           0                     0                 1 Microsoft provides programming examples for illustration only, without warranty either expressed or implied, including, but not limited to, the implied warranties of merchantability and/or fitness for a particular purpose. This article assumes that you are familiar with the programming language being demonstrated and the tools used to create and debug procedures. Microsoft support professionals can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific needs. If you have limited programming experience, you may want to contact a Microsoft Certified Partner or the Microsoft fee-based consulting line at (800) 936-5200. For more information about Microsoft Certified Partners, please visit the following Microsoft Web site:

https://partner.microsoft.com/global/30000104

For more information about the support options that are available and about how to contact Microsoft, visit the following Microsoft Web site:

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

For example, if you run the following macro, a message box displays the value of -11: Sub Imp_Example

Dim a As Integer Dim b As Integer Dim result As Integer

a =10 b = 4

result = a Imp b

MsgBox result

End Sub The value -11 is returned because the macro follows the rules in the table and uses twos complement notation. Using twos complement notation, the leftmost bit represents the sign bit. If this bit is 1, the number is negative; if this bit is 0 (zero), the number is positive. To convert a negative number from binary back to decimal, complement all of the bits (1 becomes 0 and 0 becomes 1), convert that number to decimal, change the sign of the decimal number, and then subtract 1.

In the example, where the Imp operator is used with the two numeric values 10 and 4. In binary form (2 bytes), these two numbers appear as follows:   10:   0000000000001010 4:  0000000000000100 Using the bit-wise comparison rules from the table yields the result value in binary form:   10:   0000000000001010

4:  0000000000000100   --

result:  1111111111110101 To determine the decimal equivalent of the result, use the twos complement rules of conversion as follows:                                  Result: 1111111111110101

Complement each bit: 0000000000001010

Decimal equivalent of this binary number: 10

Opposite of this number: -10 Subtract 1 (decimal value of result): -11

