**a. Control unit (CU)**

(i) It performs the actual work of computation and calculation.

(ii) The operations of arithmetic operations are addition, subtraction, multiplication, and division.

(iii) Logical operations are AND, OR, NOR, EXOR, EXNOR.

**b. The Registers**

(i) They are small storage device used by the microprocessor to hold intermediate results of addition, subtraction etc.

(ii) They are used to hold data from input or going to output units.