# Anatomy of a Digital Computer: Arithmetic Logic Unit and Control Unit

Doorsteptutor material for CBSE/Class-6 Science is prepared by world's top subject experts: fully solved questions with step-by-step explanation- practice your way to success.

## Arithmetic Logic Unit (ALU)

• It represents the fundamental building block of the central processing unit (CPU) of a computer.

• This unit is used to perform all the arithmetic and logic operations, such as addition, multiplication, comparison, etc. For example: Consider the addition of two numbers A and B. The control unit will select the number A from its location in the memory and load it into the arithmetic logic unit.

• Modern CPUs contain very powerful and complex ALUs.

• An ALU performs basic arithmetic and logic operations.

Examples of arithmetic operations: addition, subtraction, multiplication, and division.

Examples of logic operations: comparisons of values such as NOT, AND, and OR.

NOT gate

OR gate

AND gate

## Control Unit (CU)

• The control unit (CU) is a component of a computer's central processing unit (CPU) that directs the operation of the processor.

• It tells the computer's memory, arithmetic/logic unit and input and output devices.

CU Functions are as Follows

• Interprets instructions.

• Regulates and controls processor timing.

• Sends and receives control signals from other computer devices.

• Handles multiple tasks, such as fetching, decoding, execution handling and storing results.

Developed by: