The Secrets of Arithmetic... Exploring the CPU Architecture

How does a CPU perform arithmetic operations? 🤔 After all, every computer must know how to add, multiply, divide, and so on.

Everything happens inside the ALU, a component designed for this purpose. In today’s video, we explore what the ALU actually is and, more importantly, how the CPU decides what to execute. How do you define a series of instructions that the CPU runs one by one? How does the CPU even interpret an instruction?

It may seem complicated, but all of this logic works with three registers, each serving a key role in the Level 1 CPU workflow. The Accumulator stores the current numerical value, the Instruction Register stores instruction data, and the Program Counter stores the instruction address. Today we examine how each component works, and at the end we visualize the execution of a more complex code example.

⭐ What is this series about?
We start from a primitive Level 0 CPU and progress toward a more complex, pipelined Level 5 CPU. In this video, we build a Level 1 CPU that can perform multiple arithmetic operations on numbers from any memory location. In the next video, we explore the programming features introduced in Level 2.

❗Note:
This video focuses on the concepts behind how CPUs work, not on hardware-level precision. The visuals are abstract — instead of describing which gates open or which lines carry data, I simply say things like “data goes here” to keep the explanation intuitive. Real CPU architectures differ by manufacturer, but once you understand why and how they work, the technical details become much easier to grasp.

Huge thanks to everyone who helped me release this video. If you want to motivate me to create more, drop a like. ✌️

Chapters

0:00 The CPU
0:30 Arithmetic operations
1:45 Some binary theory
2:24 Instruction register
3:50 Accumulator register
4:30 Program counter
4:48 Example 1
5:05 Recap
5:20 The new clock
5:35 Example 2
6:20 Level 1 issues
6:45 Outro

Links:

video source code : https://github.com/NitaCristianu/cpu-...
Learn more ( not affiliated ): https://a.co/d/67MZ3Q3