How does a computer work?

Introduction

A computer is made up of hardware and software. Hardware means the physical parts, such as the processor, RAM, SSD, motherboard and graphics card. Software means the operating system, applications and instructions that tell the computer what to do.

Main computer components

The images below show the main parts of a desktop and laptop computer. You do not need to know every detail at first – it is enough to understand what the processor, RAM, storage, motherboard and graphics card are for.

Hardware – what does each part do?

• Processor (CPU) – executes instructions and processes data.
• RAM – temporary working memory that holds the data and programs currently in use.
• SSD or HDD – longer-term storage for the operating system, applications and personal files.
• Motherboard – connects the main components of the computer. It also contains the chip or memory that stores the UEFI or BIOS firmware, which starts immediately after the computer is powered on.
• Graphics processor/card (GPU) – helps create and display graphics and video.
• Power supply or battery – provides electrical power to the components.

What happens when you turn on the computer?

A lot happens in just a few seconds after you press the power button. For a beginner, the process can be pictured like this:

1. The computer receives power. The power supply or battery starts supplying electricity to the components.
2. UEFI or BIOS starts. This is firmware stored in special memory on the motherboard. It checks the basic hardware and determines which device should be used to start the operating system.
3. The boot loader starts. On many Linux systems this is GRUB. If several operating systems are installed, GRUB can display a menu for choosing one.
4. The Linux kernel is loaded. The kernel begins managing the processor, memory, storage devices, hardware and drivers.
5. System services start. The system prepares networking, sound, user login and other necessary functions.
6. The login screen or desktop appears. The computer is ready to use.

What does the processor actually do?

You can think of the processor as an extremely fast worker that follows instructions. It does not think like a person. Instead, it constantly performs huge numbers of simple operations: calculate a value, compare data, move data or read the next instruction.

Very simply, its work can be described as: fetch an instruction → understand it → execute it → move to the next one. This process happens extremely quickly.

RAM – working memory

RAM is the space the computer uses while it is running. When you open an application, the parts of the program and data that are needed are loaded from the SSD or HDD into RAM. The processor can then access them much faster than if it had to read everything directly from storage.

More open applications, browser tabs and large files usually mean more RAM is being used. If the system starts running short of RAM, the computer may become slower.

SSD and HDD – longer-term storage

SSDs and HDDs store the operating system, applications, documents, photos and other files even when the computer is turned off.

• SSD – faster, quieter and has no moving mechanical parts.
• HDD – slower, but often offers a lot of storage space for a lower price.

For the operating system and everyday use, an SSD is usually the better choice today. An HDD can still be useful for large collections of data or additional backups.

What happens when you open an application?

Suppose you click the Firefox icon. In a very simplified form, this is what happens:

1. the operating system finds the application on the SSD or HDD,
2. the parts that are needed are loaded into RAM,
3. the processor begins executing the application's instructions,
4. the application uses the network, storage, keyboard, mouse and other devices through the operating system,
5. the graphics system and GPU prepare the image you see on the screen.

Software

Software means the programs and systems that tell the computer what to do. Without software, a computer would only be a collection of electronic parts.

• Operating system – manages the computer and allows applications to run. Examples include Linux distributions, Windows and macOS.
• Linux kernel – the core of a Linux system that manages the processor, memory, devices and other resources.
• Applications – programs used by the user, such as a web browser, office suite or image editor.
• Drivers – software that allows the operating system to communicate with particular hardware.

How does an application reach the hardware?

An application usually does not communicate directly with every device in the computer. There are several layers between the application and the hardware.

This is why the operating system matters so much: it coordinates access to the processor, RAM, storage, graphics, sound, networking and other hardware in an organised way.

What happens when you shut down the computer?

When you choose “Shut down”, the operating system first tries to close applications safely, write the necessary data to storage and stop system services. Only then does the computer switch off the power.

Data that has been correctly saved to an SSD or HDD remains there. The working contents of RAM do not remain permanently stored without power.

Computer terms – a short glossary

These are short explanations of terms that beginners often encounter when learning about Linux, installing a system or discussing computer hardware.

Backups

A backup is a copy of important data that you can use if a drive fails, files are deleted by mistake or another problem occurs.

Conclusion

A computer is not one single part doing everything by itself. It is a system of components working together: the processor executes instructions, RAM provides temporary working space, SSD or HDD stores data, and the operating system coordinates the whole process.

Once you understand this basic picture, Linux, system installation, drivers, partitions, upgrades and troubleshooting become much easier to understand.