In order to do anything interesting, we need to be able to do more than simply shift data words from place to place. We need to be able to derive new values from the old. That is the role of the ALU. The ALU will provide several operations. Here is a partial list:

• Add
  Arithmetic addition.
• And
  Logical bitwise AND. Each bit of the two input words are ANDed.

  Bus0[n] input	Bus1[n] input	Accumulator[n] output
  0	0	0
  0	1	0
  1	1	1
  1	0	0

• XOR
  Logical bitwise Exclusive OR. Each bit of the two input words are XORed.

  Bus0[n] input	Bus1[n] input	Accumulator[n] output
  0	0	0
  0	1	1
  1	1	0
  1	0	1

• Shift
  In a Right Shift, 0 bits are inserted at the left side to take the new space.
• Rotate
  In a Right Rotate, bits which are shifted of the right side of the word are reintroduced at the left side of the word.
• Invert
  Logical bitwise invert. Every 0 bit of the word is changed to a 1. And every 1 bit is changed to a 0.

  Bus0[n] input	Bus1[n] input	Accumulator[n] output
  0	x	1
  1	x	1

Some of the operations listed above are also shown below.