Learn: The ALU - Arithmetic vs Logic

Welcome!Welcome back! You've already explored why the CPU is essential, the Fetch-Decode-Execute Cycle, and the role of registers. Today, we’ll focus on the Arithmetic Logic Unit (ALU), an essential part of the CPU.

What is the ALU?The Arithmetic Logic Unit (ALU) is a critical component of the CPU. It performs two main types of operations: arithmetic (e.g., addition, subtraction) and logic (e.g., comparisons like AND, OR, NOT).This is how the CPU processes calculations and decisions, making the ALU vital for executing instructions. It works closely with registers to store intermediate results.

How Does the ALU Work?The ALU receives data from registers. It processes this data based on the instruction (arithmetic or logic) and sends the result back to the registers or memory. This process is controlled by the Control Unit (CU), which tells the ALU what to do.

Arithmetic OperationsThe ALU performs arithmetic operations like addition, subtraction, multiplication, and division. For example, when a program calculates the total of two numbers, the ALU handles this.These operations are essential for any software that involves calculations, such as spreadsheets or games.

Logic OperationsThe ALU also performs logic operations, which involve comparisons and decision-making. Examples include:AND: Outputs 1 only if both inputs are 1.OR: Outputs 1 if at least one input is 1.NOT: Inverts the input (1 becomes 0, and 0 becomes 1).These operations are crucial for decision-making in programs, such as determining if a condition is true or false.

How Registers Help the ALURegisters like the Accumulator store intermediate results from the ALU during calculations. For example, when adding multiple numbers, the Accumulator holds the running total.This close relationship between the ALU and registers allows the CPU to perform tasks quickly and efficiently.

Why Is the ALU Important?The ALU is vital because it handles all the calculations and logical decisions that make programs function. Whether it's a simple calculation or a complex decision, the ALU is at the heart of it.Without the ALU, the CPU wouldn't be able to process data or run programs effectively.

Review Time!Great work! You've learned about the ALU, its roles, and how it works with registers. Let's test your understanding with a few final questions.