The Arithmetic & Logic Unit

The Arithmetic & Logic Unit (ALU) – The Computer’s Calculator

The Arithmetic & Logic Unit (ALU) is the critical component of a Central Processing Unit (CPU) which is to be performs all mathematical calculations and logical operations required by a computer.

Functions of the ALU

The ALU has two main functions:

1. Arithmetic Operations

Handles basic mathematical calculations such as:

• Addition (+)
• Subtraction (-)
• Multiplication (×)
• Division (÷)

Some advanced ALUs also support floating-point operations for complex mathematical calculations.

2. Logical Operations

Performs logical comparisons, including:

• AND: Returns true if both inputs are true.
• OR: Returns true if at least one input must be true.
• NOT: Reverses the input (true → false, false → true).
• XOR (Exclusive OR): Returns true if inputs are different.

These operations are essential for decision-making processes in computing.

Components of the ALU

• Operand Registers: Hold input data for operations.
• Accumulator: Stores the result of calculations.
• Status Flags: Indicate conditions such as zero result, overflow, or negative values.
• Control Signals: Direct the ALU to perform specific operations based on instructions from the Control Unit (CU).

How the ALU Works with Other CPU Components

• The Control Unit (CU) fetches an instruction and decodes it.
• The CU sends signals to the ALU to perform the necessary operation.
• The ALU processes the data and sends the result back to the registers or memory.

Importance of the ALU

• Essential for all computing tasks.
• Performs calculations for applications, gaming, and scientific computing.
• Enables logical decision-making in programming.