128 = 10000000
64  = 01000000
32  = 00100000
16  = 00010000
8   = 00001000
4   = 00000100
2   = 00000010
1   = 00000001

##</code><code>##

123 & 128 =
  01111011 (123)
& 10000000 (128)
-----------
  00000000 (0)
= 0

123 & 64
  01111011 (123)
& 01000000 (64)
-----------
  01000000 (64)
= 64

123 & 32
  01111011 (123)
& 00100000 (32)
-----------
  00100000 (32)
= 32

And so on...