Re: Fun with Binary Numbers

Well, to begin with applying the mask 1111 0000 to 1101 0100 0110 0110 is going to give you 1100000 not 110. But you can shift the result to the right 4 if that is the result you want. There is no algorithm to speak of here, just apply the mask. Like this: $num = "1101010001100110"; $mask = "11110000"; $result = bindec($num) & bindec($mask); echo decbin($result); If you want only the second quartet of the result, do: $result = $result>>4; -Rasmus On Wed, 28 Aug 2002, David Buerer wrote: > Here's a question, > > Say I have a binary number like this > > 1101 0100 0110 0110 > > And I want to pull out of the binary number the third quartet (is that the > right word) > > I want to know how to apply the mask > > 0000 1111 0000 0000 > > to the number above so that the result would be > 0100 > > Likewise, given > the number: 1101 0100 0110 0110 > and the mask 0000 0000 1111 0000 > the result 0110 > > I suppose this is the same algorithm used to separate the host from the node > address given an IP address and a subnet mask. I just need to know what the > algorithm is. > > Thanks > David > >