On 2011-11-21, David Riley <[email protected]> wrote:
> On Nov 21, 2011, at 2:29 PM, Matthew Lenz wrote:
>
>> Another thing I noticed is that the & and | appear to give the same result
>> as adding or subtracting 128 from the ordinal value. I'm assuming that
>> isn't coincidence. :)
>
> It's not, though the difference is important. They're binary ANDs (&) and
> ORs (|), so (0x0F | 0x80) = 0x8F, but (0x8F | 0x80) = 0x8F as well, whereas
> (0x8F + 0x80) = 0x10F. For manipulating bit values (which is what you're
> doing, you should almost never be adding or subtracting, but rather ANDing
> and ORing (or XORing, but not nearly as often).
>
> Just in case you're not familiar, 0x is the prefix for a hexadecimal number.
> 0x80 = 128, which is binary 10000000 (i.e. the high bit in a byte).
Like the old joke:
There are 10 kinds of people in the world: those who understand
binary numbers, and those who don't.
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