Question

I am working on a little Hardware interface project based on the Velleman k8055 board.

The example code comes in VB.Net and I’m rewriting this into C#, mostly to have a chance to step through the code and make sense of it all.

One thing has me baffled though:

At one stage they read all digital inputs and then set a checkbox based on the answer to the read digital inputs (which come back in an Integer) and then they AND this with a number:

i = ReadAllDigital cbi(1).Checked = (i And 1) cbi(2).Checked = (i And 2) \ 2 cbi(3).Checked = (i And 4) \ 4 cbi(4).Checked = (i And 8) \ 8 cbi(5).Checked = (i And 16) \ 16 

I have not done Digital systems in a while and I understand what they are trying to do but what effect would it have to AND two numbers? Doesn’t everything above 0 equate to true?

How would you translate this to C#?

Answer 1

I think you ‘ll have to translate it to this:

i & 1 == 1  i & 2 == 2  i & 4 == 4  

etc… This is using the bitwise AND operator.

When you use the bitwise AND operator, this operator will compare the binary representation of the two given values, and return a binary value where only those bits are set, that are also set in the two operands.

For instance, when you do this:

2 & 2

It will do this:

0010 & 0010 

And this will result in:

 0010  0010 &----  0010 

Then if you compare this result with 2 (0010), it will ofcourse return true.