I need help on Bit Twiddling

Question

I love to see people writing Bit Twiddling code but I just can\'t understand it at all. Gone through Hacker\'s Delight and http://graphics.stanford.edu/~seander/bithacks.html, b

Answer 1

What is the easiest way to calculate the output of bits for example 1 | 2 = 3.

Write out the numbers as binary. This is how the numbers are really represented.

  00000001
| 00000010
= 00000011

Answer 2

You're gonna have to study a little, but here's a little cheat sheet to know the number in binary form

128 | 64 | 32 | 16 | 8 | 4 | 2 | 1

If you want 3, go from left to right, filling up in the spaces that contains the values you need to create the number 3

128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
                             X   X

2 + 1 = 3 so you replace the ones marked with X with 1s and the rest with 0s

00000011

The same for the number 2:

128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
                             X

And the binary result is.

00000010

For the number 47:

128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
            X        X   X   X   X

Binary result:

00101111

This is not a rule, or formula or anything. It's just something to help you convert numbers a little faster, and practice it in your head. You'll still need to study a lot if you want to play with bits :-)