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

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## 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.