IIF function in VBA

Question

I am debugging some VBA code and I have an IIF function which I don't understand what is doing. It's IIF(constant And i, "TRUE", "FALSE"), where I gets values from 0 to n.

I know that this function is equivalent to IF in Excel. But in this case what is the condition? What does the expression number and number means? I run this sample:

Sub Sample()    
    For i = 0 To 20  
        Cells(i + 1, 1) = i
        Cells(i + 1, 2) = 4 And i
    Next i     
End Sub

And I get the values below:

Answer 1

The expression 4 And i will do an arithmetic AND-operation. Example:

     6:  0 0 0 0 0 1 1 0
     4:  0 0 0 0 0 1 0 0
Result:  0 0 0 0 0 1 0 0

    11:  0 0 0 0 1 0 1 1
     4:  0 0 0 0 0 1 0 0
Result:  0 0 0 0 0 0 0 0

So 6 AND 4 is 4 while 11 AND 4 is 0.
Now 0 is seen as False and everything not 0 is seen as True. Used in an IIF-statement, all numbers that have the 3rd bit (counting from right) set will execute the True-part of the IIF, all others the False.

Answer 2

Your And operator does a bit wise comparison:

result = expression1 And expression2  

When applied to numeric values, the And operator performs a bitwise comparison of identically positioned bits in two numeric expressions and sets the corresponding bit in result according to the following table.

If bit in expression1 is	And bit in expression2 is	The bit in result is
1	1	1
1	0	0
0	1	0
0	0	0

Since the logical and bitwise operators have a lower precedence than other arithmetic and relational operators, any bitwise operations should be enclosed in parentheses to ensure accurate results.

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So converting the 4 into binary it results in 100. I have done that in the 3ʳᵈ column below, where I converted all numbers of the 1ˢᵗ column to binaries. The other 2 columns are just filled up with zeros for better visibility:

So watching the table above you only get a 1 as result if both bits in the same position are a 1 otherwise you get a 0. That means you always get a 4 as result if 4 and i has a 1 in the 3ʳᵈ bit from the right due to the bitwise comparison (see the red bits).