2's complement 
11110110

What value is this in decimal as a positive?

1's complement
00001001

add 1 
     0001
  00001001
+        1
-----------
  00001010      

1x2^3 + 0x2^2 + 1x2^1 + 0x2^0
1x8   + 0x4   + 1x2   + 0x1
8     + 0     + 2     + 0
10 (decimal)


=-=-=-=-=-=-=-=-=-=-=-=-= 
  00001100   ->   00001100         12
- 00000011   (need 2's comp)        3
----------


00000011 -> 11111100
+1                 1
           ---------
            11111101

                  1111100 
  00001100   ->   00001100
- 00000011      + 11111101
----------      ----------
                1 00001001

                         9 decimal

12 - 3 = 9
=-=-=-=-=-=-=-=-=-=-=-=-= 

truth table

A B | A AND B
-------------
0 0 | 0
0 1 | 0
1 0 | 0
1 1 | 1

    00101100   
AND 00100011  
------------ 
    00100000


A B | A OR B
-------------
0 0 | 0
0 1 | 1
1 0 | 1
1 1 | 1

    00101100   
OR  00100011  
------------ 
    00101111


A | NOT A
----------
0 | 1
1 | 0

NOT 00101100 = 11010011