Splitting up bytes question

[HenrikOlsson]

Hi,
Yes, it should of course be Number_2 = FullByte & %00001111, typo on my behalf, sorry about that.

If you do Number_1 = FullByte & %11110000 you'll mask off the lower four bits (make them zeros) and assign the result to Number_1. In this case, when FullByte is 178 (10110010), you'd end up with 10110000 which 176 and not 11 which is what you're looking for.

/Henrik.

[ERMEGM]

So, with the shift (>>4), you'd go from 11110101 to 00001111 (for 15). But with & %11110000, you'd get 11110000 for Number_1.

I thought %11110000 meant it would discard bits 0-3 and just enter 1111 into the Number_1 value. Apparently that's not the case.

Tony

[HenrikOlsson]

Hi Tony,
Yes, the & operator is bitwise AND.

As input it takes two numbers, it then compares them bit by bit. Think of it like having running each bit in both numbers to a two-input AND-gate, (8 gates, one for each bit) the output of each gate is wired into the result variable. Just as with a real AND-gate both inputs (the same bit in the two numbers) have to set in order for the output (the bit in the result) to be set.

Result = %10101010 & %11111111
Here Result be a copy of the first number because all bits in the second number is set. Any bit which is SET in both numbers will be set in the result.

Result = %10101010 & %0000000
Here Result will be all zeros because the second number is all zeros.

Result = %10101010 & %11110000
Here Result will be %10100000 be because only the four bits of the second number are set.

Result = %10101010 & %00111100
Here Result will be 00101000 because, well I suppose you get it by now ;-)

/Henrik.

[ERMEGM]

Makes total sense. Thank you so much guys for your help. While the book is helpful, it doesn't always break things down on a lower level for all people to understand. That's why these boards are so helpful, you can always find someone able to better present the information. Thanks again.

Tony