LFTHQ

How Do Computers Work for Kids?

For ages 8–12, parents, and educators · About 5 minute read

A computer can play a song, show a video, and help you write a story. Underneath, it is doing something much simpler: following instructions, one small step at a time, very quickly. This guide explains the main parts and how they work together.

Every computer does four jobs

A laptop, a phone, a tablet, and a game console look different, but they all do the same four things:

  • Input: taking in information.
  • Processing: following instructions to work on that information.
  • Storage: keeping information for later.
  • Output: showing or sending out a result.

The physical parts you can touch are called hardware. The instructions that tell the hardware what to do are called software.

The CPU: the part that follows instructions

The CPU, or central processing unit, is a small chip that carries out instructions. People sometimes call it the brain of the computer, but it does not think. It does very simple things, such as adding two numbers, comparing two values, or moving a piece of information from one place to another.

What makes a CPU powerful is speed. A modern CPU can carry out billions of these tiny steps every second. Many CPUs also have several cores, which let them work on more than one task at the same time.

Good to know

Inside a computer, all information is stored as bits. A bit can only be 0 or 1. Letters, numbers, pictures, and sounds are all stored as long patterns of bits.

RAM: the working memory

RAM stands for random-access memory. It holds the information the computer is using right now, such as the apps that are open and the document you are editing. RAM is very fast, so the CPU can reach what it needs without waiting.

RAM is temporary. When the computer is switched off, everything in RAM is cleared.

Storage: keeping things for later

Storage is where the computer keeps things when they are not in use: apps, photos, videos, saved games, and files. Most new computers use a solid-state drive, or SSD. Storage is slower than RAM, but it keeps its contents when the power is off.

RAM or storage?

Picture a desk and a bookshelf. The desk is RAM: it holds what you are working on, and it gets cleared at the end of the day. The bookshelf is storage: it holds much more, and everything stays there until you take it down. This is why work you have not saved can be lost if the power goes out. It was only on the desk.

Input and output

Input devices send information into the computer. Keyboards, mice, touchscreens, microphones, cameras, and game controllers are all input devices.

Output devices present results. Screens, speakers, headphones, and printers are output devices. A touchscreen is both: you touch it to give input, and it shows output.

Software: the instructions

Hardware cannot do anything useful without instructions. Software is the name for those instructions. A piece of software is also called a program or an app. A drawing app, a game, and a web browser are all software.

Programs are written by people called programmers. A program is a long, exact list of steps. Computers follow those steps exactly, which is why a small mistake in a program, called a bug, can cause strange behavior.

The operating system

The operating system is the main software that runs the whole computer. Windows, macOS, Linux, ChromeOS, Android, and iOS are operating systems. The operating system:

  • starts up when the computer is turned on,
  • lets you open and close apps,
  • shares the CPU and RAM between the apps that are running,
  • organizes files and folders in storage,
  • and passes messages between apps and hardware such as the keyboard and screen.

Apps do not talk to the hardware directly. They ask the operating system, and it does the work for them.

How the parts work together

The main parts are connected through a large circuit board called the motherboard. Information moves between them all the time:

  1. Input arrives from a device such as a keyboard.
  2. The operating system passes it to the right app.
  3. The CPU follows the app’s instructions, using RAM to hold what it is working on.
  4. Results are sent to an output device, saved to storage, or both.

This loop repeats many times every second.

Example: typing a story and saving it

Imagine Maya is writing a story for school.

  1. She opens the writing app. The operating system copies the app from storage into RAM so the CPU can run it.
  2. She presses the M key. The keyboard sends a signal that means “this key was pressed.” That is input.
  3. The CPU processes it. Following the app’s instructions, the CPU adds the letter to the story, which is held in RAM.
  4. The screen updates. The computer works out which tiny dots on the screen, called pixels, should change so that the letter M appears. That is output.
  5. She saves her work. The story is copied from RAM to storage as a file. Now it will still be there tomorrow.
  6. She closes the app. The space it used in RAM is freed for something else.

If the battery had run out before step 5, the story would have been lost, because RAM does not keep its contents without power.

Why computers sometimes slow down

Knowing the parts helps explain everyday problems:

  • Too many apps open: RAM fills up, and the computer has to keep moving things in and out of it.
  • A demanding task: the CPU is busy and other work has to wait.
  • Storage almost full: there is little room left for the computer to work with.
  • Heat: a hot computer may slow itself down on purpose to protect its parts.

Questions to talk about

Parents and teachers can use these to check understanding:

  • Name three input devices and three output devices you used today.
  • What is the difference between RAM and storage?
  • Why does a computer need an operating system?
  • What happens, step by step, when you take a photo with a tablet?