By the end of this lesson you will be able to
- Explain in your own words what a computer is and what it does.
- Name the four jobs of every computer: input, processing, storage and output.
- Tell hardware from software, and give an example of each.
- Recognise a laptop, desktop, tablet and smartphone as computers, and say what each is best for.
Almost everything you will learn in this academy rests on one simple idea. If you understand what a computer actually does, then buttons, menus and error messages stop looking like magic and start making sense. This lesson gives you that idea, using things you already know from everyday life.
A computer is a machine that follows instructions
A computer is a machine that takes in information, works on it by following instructions, keeps it for later, and shows you the result. That is all. A calculator does a tiny version of this. A laptop does an enormous version of it, very quickly, using instructions written by people.
Think of a kitchen. You bring in ingredients, you follow a recipe, you put leftovers in the fridge, and you serve a meal. A computer does the same with information instead of food: the ingredients are your typing and clicks, the recipe is a program, the fridge is storage, and the meal is what appears on the screen.
- Step 1: InputYou give it information: typing, clicking, speaking
- Step 2: ProcessingIt follows instructions to work on the information
- Step 3: StorageIt keeps results so they are there next time
- Step 4: OutputIt shows you the result: screen, sound, print
Read this figure as text
A flow diagram of four boxes joined by arrows: input, processing, storage and output.
Four steps in a row. Step 1, Input: you give the computer information, for example by typing or clicking, like bringing ingredients into a kitchen. Step 2, Processing: the processor follows instructions to work on that information, like following a recipe. Step 3, Storage: results are kept so they are still there later, like putting food in the fridge. Step 4, Output: the computer shows you the result on the screen or through the speakers, like serving the meal.
One everyday example, step by step
Suppose you type a short letter and print it. Every one of the four jobs happens, in order, and you can name each one.
- Step 1: You typeEach key press is input
- Step 2: Letters appearThe processor turns key presses into text
- Step 3: You press SaveThe file is written to storage
- Step 4: You press PrintA paper copy is the output
Read this figure as text
A flow diagram showing typing a letter, the computer arranging the letters, saving the file, and printing it.
Step 1: you type the words of a letter on the keyboard (input). Step 2: the processor turns each key press into letters on the page and keeps track of the layout (processing). Step 3: you press Save, and the document is written to storage so it survives switching off (storage). Step 4: the words appear on the screen as you type, and a printer produces a paper copy when you press Print (output).
Hardware and software
Everything in the picture above falls into one of two families. Hardware is anything you can physically touch: the screen, keyboard, the chips inside. Software is the instructions that tell the hardware what to do. You cannot touch software, but you can see what it does. Hardware without software is a useless box; software without hardware has nothing to run on.
- Screen, keyboard, touchpad, mouse
- Processor (CPU) and memory (RAM)
- Storage drive (SSD or hard disk)
- Battery, charger and cables
If you can drop it on your foot, it is hardware.
- Operating system: Ubuntu, Windows, macOS
- Applications: browser, word processor
- Your documents, photos and settings
- Updates and drivers
You cannot touch it, but you can see what it does.
Read this figure as text
Two columns comparing hardware examples and software examples.
Hardware, the parts you can touch: the screen, the keyboard, the touchpad or mouse, the processor chip, memory, the storage drive and the battery. Software, the instructions that run on the hardware: the operating system (for example Ubuntu or Windows), applications such as a web browser or a word processor, and the files and settings they use. An analogy: a music player is hardware, and the songs it plays are like software.
Many kinds of computer
Laptops, desktops, tablets and smartphones are all computers. They follow the same four jobs, but are shaped for different situations. A phone is a computer you can fit in a pocket; a desktop trades portability for power and a bigger screen.
- LaptopPortable, battery powered, keyboard built in. Best all-rounder for study and work.
- DesktopStays on a desk. Often more power for the price and easier to repair.
- TabletTouchscreen slab. Good for reading, drawing and watching.
- SmartphoneA computer in your pocket that also makes calls.
Read this figure as text
Four cards showing a laptop, desktop, tablet and smartphone, each with a short description.
Laptop: portable, with a keyboard and screen built in and a battery; good for study and work anywhere. Desktop: a separate screen, keyboard and case; stays on a desk, often more powerful for the price, easier to upgrade. Tablet: a touchscreen slab without a built-in keyboard; good for reading, drawing and video. Smartphone: a pocket-sized touchscreen computer that also makes calls; good for communication, photos and quick tasks.
Meet the parts of a laptop
Here is a laptop with its main parts numbered. Tap a name in the list to highlight its number on the picture. Notice which parts are for input (keyboard, touchpad, webcam) and which are for output (display, speakers).
Read this figure as text
An open laptop drawn from the front with six numbered parts: display, webcam, keyboard, touchpad, power button and speakers.
Marker 1 is the display, the screen that shows output. Marker 2 is the webcam above the screen, an input device for video. Marker 3 is the keyboard, the main input device for typing. Marker 4 is the touchpad, which moves the pointer. Marker 5 is the power button, at the top right of the keyboard area on this drawing. Marker 6 is the speakers, the sound output.
Common mistakes
✖ Instead of: Thinking that “the computer” means only the screen.
✔ Do this: The screen is just the output. The computer is the whole system: processor, memory, storage and software, plus the devices you connect.
✖ Instead of: Believing a computer is intelligent and understands what you mean.
✔ Do this: A computer follows exact instructions very fast. When it does something silly, an instruction or a piece of input was wrong or missing.
✖ Instead of: Using “hardware” and “software” as if they meant brand and model.
✔ Do this: Hardware is the physical parts; software is the instructions. A brand is neither.
If something goes wrong
- I cannot tell whether something is hardware or software.
- Ask: could I pick it up? If yes it is hardware. If it is a program, a file or a setting, it is software.
- My device does not have a keyboard.
- Tablets and phones use an on-screen keyboard on the touchscreen. It still counts as an input device.
Key terms
- Computer
- A machine that takes in information, works on it by following instructions, stores it and shows you the result.
- Hardware
- The physical parts of a computer that you can touch.
- Software
- The instructions that tell hardware what to do. You cannot touch it.
- Input device
- A device you use to give information to a computer.
- Output device
- A device the computer uses to show or give you its results.
Practise it for real
Reading is not the same as being able to do it. Complete these on your own computer, then tick only what you have actually done. These ticks are your own honest record: nothing checks them for you.
Find the four jobs on your own device
Sit with your laptop (or phone). Open any program, type a few words, save them, and then close the program. While you do it, say out loud which of input, processing, storage or output each action is. Then point to three hardware parts and name one piece of software that is currently running.
Challenge: explain a computer to someone else
Without looking at the lesson, explain to a friend or family member what a computer is, using your own comparison instead of the kitchen. Include the four jobs and the difference between hardware and software. If they understand, you have understood it.
Knowledge check
6 questions. You need 80% to pass. Mistakes here are part of learning, and you can retry as often as you like.
Summary
- A computer takes in information, processes it by following instructions, stores it and outputs the result.
- Hardware is what you can touch; software is the instructions that run on it.
- Laptops, desktops, tablets and smartphones are all computers shaped for different uses.
- Asking “is this input, processing, storage or output?” helps you work out where a problem is.
Checklist: can you do these?
Marking a lesson as read does not prove you can do it. Skills count as demonstrated when you pass the quiz (not yet) and complete the practical tasks (not yet).
Related lessons
References and further reading
Official sources for details that can change between versions.
- Computer (overview) (Encyclopaedia Britannica)
- Computer basics for beginners (GCFGlobal)