What Is a Computer System?
On this page 7 headings
Start here Your phone, a smart watch, a washing machine, a drone, a self-driving car, even a smart speaker. They look completely different. But inside, every one of them does the same three jobs: it computes, it remembers, and it communicates. This course shows you how to build such a machine from the very bottom.
A computing system is any machine that takes in information, works on it, and gives out a result. Today they are inside almost everything: phones, watches, cars, robots, TVs and fridges.
They also keep getting more complex. A Nokia 3310 phone (2000) could make calls and send SMS. A smartphone from the 2020s has a camera, GPS, internet, AI features and billions of tiny switches inside.
The good news: however complex they get, the basics stay the same. If you understand the basics well, you can understand any computer.
| Block | Job | Simple example |
|---|---|---|
| Computing unit | Does the work: adds, compares, decides | The calculator part of your phone |
| Memory / storage unit | Keeps information | Your photos and contacts |
| Communication unit | Moves information in and out | Wi-Fi, the screen, the keyboard |
The idea of a computer built from these parts goes back to a famous 1946 report by Burks, Goldstine and von Neumann on how to design an electronic computer.
To solve problems. We use computers to get answers we couldn’t easily work out by hand: weather forecasts, bank balances, the path of a rocket, the shortest route on a map.
By moving electrons around.
Deep inside, a computer is just a huge number of tiny switches (called transistors). Each switch lets electricity flow (ON) or blocks it (OFF). By turning billions of switches on and off in the right pattern, the computer does maths, shows pictures and runs apps.
So how does a problem become electrons? Step by step, through layers.
Start at the top with a problem, and keep going down until you reach electrons:
| Layer (top to bottom) | What it means | Example |
|---|---|---|
| Problem | What we want to solve | “Add up my monthly bills” |
| Algorithm | Step-by-step method | Start at 0, add each bill one by one |
| Program | Algorithm written in a language | A few lines of Python or C |
| System software | Turns the program into machine instructions | Compiler, operating system |
| Instruction set | The commands the chip understands | ADD, LOAD, STORE |
| Microarchitecture | How the chip carries out each command | Which parts switch on, in which order |
| Logic | Gates that do AND, OR, NOT | ← this course |
| Circuits and devices | Transistors and wires | Tiny switches on silicon |
| Electrons | The physics at the bottom | Charges moving |
- Computer science usually works at the top layers (algorithms, programs).
- Electrical engineering works at the bottom (devices, physics).
- Computer engineering sits in the middle and joins the two. This course lives here.
Why this matters for you: you can write better software if you understand the hardware, and design better hardware if you understand the software.
The course has four modules:
| Module | Topic |
|---|---|
| 1 | Foundations: the digital world, logic gates, Boolean algebra, computer arithmetic |
| 2 | Combinational logic: circuits with no memory, leading up to an ALU (the part that does maths) |
| 3 | Sequential logic: circuits with memory, timing and the clock |
| 4 | Processor design: putting it all together into a simple CPU and its instruction set |
The goal: you will design a simple CPU yourself, with its arithmetic unit, timing and control.
Textbooks:
- Digital Logic and Computer Design by M. Morris Mano (main book)
- Digital Design and Computer Architecture, ARM Edition by Sarah L. Harris and David Money Harris (for further reading)
In one line: Every computer computes, remembers and communicates, and a problem reaches the hardware by going down layers from algorithm to electrons. This course covers the logic layer, all the way up to a simple CPU. Exam words: computing system, computing unit, memory unit, communication unit, transistor, switch (ON/OFF), transformation hierarchy, algorithm, instruction set, microarchitecture, logic, computer engineering, combinational, sequential, CPU, ALU.