Let's assume you must test whether the most significan bit of an integer value is set or not. This is the code that you usually write:

```
' two cases, depending on whether the value is Integer or Long
If intValue And &H8000 Then
' most significant bit is set
End If
If lngValue And &H80000000 Then
' most significant bit is set
End If
```

However, all VB variables are signed, therefore the most significant bit is also the sign bit. This means that, regardless of whether you're dealing with an Integer or a Long value, you can test the most significant bit as follows:

```
If anyValue < 0 Then
' most significant bit is set
End If
```

On the other hand, when you're testing the sign of two or more values you can often simplify and optimize the expression by applying a bit-wise operation to the sign bit. Here are several examples that demonstrate this technique:

```
' Determine whether X and Y have the same sign
If (x < 0 And y < 0) Or (x >= 0 And y >=0) Then ...
' the optimized approach
If (x Xor y) >= 0 Then
' Determine whether X, Y, and Z are all positive
If x >= 0 And y >= 0 And z >= 0 Then ...
' the optimized approach
If (x Or y Or z) >= 0 Then ...
' Determine whether X, Y, and Z are all negative
If x < 0 And y < 0 And z < 0 Then ...
' the optimized approach
If (x And y And z) < 0 Then ...
' Determine whether X, Y, and Z are all zero
If x = 0 And y = 0 And z = 0 Then ...
' the optimized approach
If (x Or y Or z) = 0 Then ...
' Determine whether any value in X, Y, and Z is non-zero
If x = 0 And y = 0 And z = 0 Then ...
' the optimized approach
If (x Or y Or z) = 0 Then ...
```

It is mandatory that you fully understand how the boolean operators work before using them to simplify a complex expresion. For example, you must be tempted to consider the two following lines as equivalent:

```
If x <> 0 And y <> 0 Then
If (x And y) Then ...
```

You can easily prove that they aren't equivalent if using X=3 (binary 0011) and Y=4 (binary 0100). In this case, however, you can partially optmize the expression as follows:

```
If (x <> 0) And y Then ...
```