Parts of a Computer and Their Functions (With Diagram)

Knowing about the parts of a computer and their functions gives you a good start on knowing how computers work. It will set you up to take further steps to find out more about computer hardware later on.

The motherboard, CPU, memory, storage, and cooling system all work together, and each part has a clear job.

Even though this guide is about desktop computers, laptops use many of the same parts. The primary differences are that the screen, keyboard, battery, speakers, and touchpad are built into one body.

1. CPU (Central Processing Unit)

The CPU, or central processing unit, is the brain of the computer. It carries out the instructions your computer is given. Every time you click a button, open a file, or load a webpage, the CPU handles those commands billions of times each second. A part inside it called the arithmetic logic unit (ALU) does the math and the yes or no decisions that software needs.

In a desktop, the CPU sits in a socket on the motherboard. Modern CPUs from Intel and AMD have several cores, which lets them work on more than one task at the same time.

• Coordination: Tells the rest of the system what work to do.
• Performance impact: Affects how fast the PC feels, how smoothly games run, and how many apps you can use at once.

The CPU and the graphics card work together as a team, so a weak CPU can hold back a strong GPU and cause a performance bottleneck. If yours is crashing or behaving oddly, here is how to check whether the CPU is working properly.

2. Motherboard

The motherboard is the main circuit board inside your computer. Every other part either plugs into it or connects to it, and its job is to hold those parts together and move data and power between them. It holds the CPU, the memory slots, the expansion slots, the chipset, and the BIOS or UEFI firmware.

• CPU socket: Holds the processor.
• RAM slots: Hold the memory sticks.
• PCIe slots: Connect graphics cards, add-on cards, and some fast storage drives.
• Chipset: Controls which features and ports the board can use.
• I/O panel: The row of ports at the back for plugging in outside devices and networking.

3. Power Supply Unit (PSU)

The PSU, or power supply unit, changes the high-voltage power from your wall outlet into the lower-voltage power your PC parts can safely use. Cables from the PSU carry that power to the motherboard, CPU, graphics card, storage drives, and fans.

Safety features built into the power supply also help protect your parts from power surges and voltage problems. Because the PSU has to provide enough power for everything in the build at once, a PSU wattage calculator can help you work out how much power your parts need. If you are curious what all that draw costs to run, we break down how much energy a gaming PC uses.

4. RAM (Random Access Memory)

RAM, or random access memory, is the fast short-term memory your computer uses for whatever you are doing right now. When you open a browser, start a game, edit a document, or switch between programs, the data in use is kept in RAM. The CPU can reach RAM far more quickly than it can reach a storage drive, which is why RAM is used for active work.

RAM is volatile, which means everything in it is wiped when the computer turns off. The more RAM a computer has, the more things it can keep open and work on at the same time.

5. Storage: SSDs, HDDs, and Portable Drives

Storage is the long-term memory for your operating system, apps, games, photos, documents, and backups. Unlike RAM, storage keeps your data safe even when the computer is turned off.

Hard Disk Drives (HDDs)

A hard disk drive stores files on spinning magnetic disks that a small read/write head moves across. Because of the moving parts, HDDs are slower and easier to damage than SSDs, but they can hold a large amount of data, which makes them handy for backups and media libraries.

Solid State Drives (SSDs)

A solid-state drive stores files on flash memory chips and has no moving parts. Because it has nothing to spin up, an SSD reads and writes data much faster, which makes the whole computer feel quicker as Windows, apps, and games all load more quickly.

Portable Storage Devices

Portable storage devices let you move files from one computer to another. USB flash drives are handy for documents and installers, SD cards are common in cameras and laptops, and external hard drives or external SSDs are used for backups and large files.

6. GPU (Graphics Processing Unit)

The GPU, or graphics processing unit, draws everything you see on the screen. From desktop windows to videos and 3D games, the graphics card works out and draws every single pixel. While the CPU is best at handling complex tasks one step at a time, the GPU is built to handle thousands of simpler tasks all at once, which is exactly what drawing an image needs.

• Dedicated graphics card: A separate card with its own video memory. Used for gaming, 3D work, and creative apps.
• Integrated graphics: Built into the processor. Uses less power and is fine for office work and watching videos.
• VRAM: The graphics card's own memory, used to hold textures and images while they are being drawn.
• Display outputs: HDMI, DisplayPort, and USB-C connections that send the picture to monitors and TVs.

7. Input and Output Devices

Input Devices

Input devices send information and commands to the computer.

• Keyboard: Sends text and shortcut commands.
• Mouse or touchpad: Controls the pointer and what you click on.
• Microphone: Picks up voice and other audio.
• Webcam: Records video for calls, streaming, and recording.
• Scanner: Turns paper documents into digital files.
• Game controller or joystick: Gives you smooth control for games and simulators.

Output Devices

Output devices show or play results back to the user. The monitor is the main output device, but speakers, printers, and projectors are output devices too.

• Monitor: Shows the desktop, videos, games, and apps.
• Speakers or headphones: Play sound from the sound card or built-in audio.
• Printer: Makes paper copies of text and images.
• Projector: Shows the screen image on a large surface.

8. Computer Case

The computer case holds all the parts together in one place and protects them from dust, knocks, and bumps. It also guides air through the system to keep parts cool, holds the storage drives, gives you places to mount fans, and provides the front buttons and ports you use every day.

• Cable routing: Channels behind the motherboard tray keep cables tidy and out of the way of airflow.
• Dust filters: Mesh filters over the air intakes stop dust from building up inside.

9. Cooling and Airflow

Cooling matters because the CPU and GPU make a lot of heat when they work hard. If temperatures climb too high, the computer may slow down through thermal throttling, where the chip slows itself down to cool off, or it may crash or shut down to protect itself. The job of the cooling system is to move that heat away before it becomes a problem.

Most systems use air cooling. A heatsink sits on top of the processor, the heat spreads into its metal fins, and a fan blows air across them to carry the heat away. Case fans then pull cool air in and push warm air out. Liquid cooling does the same job using a pump, liquid coolant, and a radiator to move heat away from the hottest parts.

• Stock cooler: The basic cooler that comes included with some processors.
• Tower air cooler: A larger add-on heatsink with one or two fans.
• AIO liquid cooler: A sealed liquid cooler with a pump and a radiator.
• Thermal paste: Fills the tiny gaps between the CPU and the cooler so heat passes across more easily. The same compound sits under a graphics card cooler, and replacing dried GPU thermal paste is a common way to cool an overheating card.

Good fan placement is the best way to stop heat from building up. Balanced airflow in and out keeps temperatures down and helps stop dust from getting in through the gaps in the case.

10. Connectivity, Ports, and Networking

Today's computers use wired and wireless connections to get on the internet, share files, connect other devices, and send video to displays. Some ports are built into the motherboard, while others come from the case, graphics card, add-on cards, or external adapters.

Wired Connections

Ethernet connects a computer directly to a router, modem, or network switch. A wired connection is usually faster and more reliable than Wi-Fi, which is why it is the better choice for gaming, large file transfers, and stable video calls.

If several people share the same connection, an internet speed requirements calculator can help estimate how much bandwidth the household actually needs.

Wireless Connections

Wi-Fi connects laptops and desktops to a wireless router without cables. Bluetooth is used for short-range devices such as keyboards, mice, headphones, speakers, and controllers.

Common Ports and Connectors

• USB: Common port for devices, storage, charging, and accessories.
• USB-C: A connector that plugs in either way. Used for data, charging, displays, and docks, depending on what the device supports.
• HDMI: Carries video and audio to monitors and TVs.
• DisplayPort: Common on graphics cards and high-refresh-rate monitors.
• Ethernet: RJ-45 network port for wired internet and home networks.
• Audio jacks: 3.5mm ports for microphones, headphones, speakers, and line-in devices.

Prefer to watch? Here is a summary video covering these components.