In this guide
- What is computer hardware?
- Types of computers
- The main components of a computer
- How the components work together
- Input, output and peripheral devices
- Ports and connectors
- Firmware, BIOS and UEFI
- Server hardware vs desktop hardware
- Network cabling and structured wiring
- Identifying and troubleshooting hardware
- Hardware terms worth knowing
- FAQ
Computer hardware basics, from the power button to the desktop
Computer hardware basics are the physical parts of a computer and what each one does: a processor that calculates, memory that holds work in progress, storage that keeps it, a motherboard that connects them, and a power supply that feeds them all.
A phone, a laptop, a desktop and a rack server are the same parts in different packages, which is why learning them once explains every device.
This guide covers the hardware fundamentals in the order they make sense: what computer hardware is, hardware versus software and firmware, the main components, how they work together when a computer starts, input and output devices, ports and connectors, firmware and the boot process, server hardware, network cabling, and how to identify and troubleshoot what you have. Each section links to a full page in this library.
DefinitionWhat is computer hardware?
Computer hardware is every physical part of a computer system: the components inside the case and the devices attached to it. If you can touch it, it is hardware. It is usually divided into internal hardware, such as the processor and memory, and external hardware or peripherals, such as the keyboard and monitor.
Hardware vs software is the first distinction to get straight. Computer hardware does nothing alone: software tells it what to do, and firmware sits between the two. Three layers work together in all computers:
| Layer | What it is | Example | Changed by |
|---|---|---|---|
| Hardware | The physical components | Processor, memory, drive, motherboard | Replacing the part |
| Firmware | Software stored on a chip in the hardware that tells it how to start and operate | BIOS or UEFI on a motherboard, the firmware in a drive or router | A firmware update |
| Software | The operating system and the applications that run on it | Windows, Linux, a web browser | Installing or updating |
FormsTypes of computers
The same computer hardware components are packaged differently depending on the job:
- Desktop computers put standard, replaceable parts in a case, which makes them the cheapest to repair and upgrade.
- Laptops trade upgradeability for portability: the processor and often the memory are soldered to the board.
- Workstations are desktops built for heavy processing, with more cores, more memory and professional graphics.
- Servers provide services to other computers and are built to run continuously.
- Phones and tablets combine the processor, memory and graphics in a single chip to save power.
- Embedded computers sit inside other equipment, from routers to cars, and run one job.
ComponentsThe main components of a computer
Every general-purpose computer has the same basic components, and a fault in any one of them produces a recognizable symptom.
| Component | What it does | When it fails |
|---|---|---|
| CPU, the central processing unit | The processor: it executes instructions and does the information processing. Speed depends on the number of cores, the clock speed and the cache | No boot, or crashes under load, often from overheating |
| Motherboard | The main circuit board that connects every other part and carries the chipset and firmware | No power, no display, or random faults across devices |
| RAM, random access memory | Holds the programs and data in use. Fast and volatile: it empties when the power goes off | Beep codes at startup, blue screens, corrupted data |
| Storage drive | Keeps the operating system, applications and files permanently, on an SSD or a hard disk | Slow operation, missing files, no boot device |
| Power supply unit | Converts mains power to the low voltages the components use | No power at all, or restarts under load |
| GPU, the graphics processing unit | Draws the display, and accelerates video, 3D and some computation. Built into the processor or a separate card | No display, artifacts on screen, driver crashes |
| Network adapter | Connects the computer to a wired or wireless network | No link, or an intermittent connection |
| Cooling | Fans, heat sinks and sometimes liquid loops that remove heat | Throttling, noise, shutdowns |
Two of these decide how fast a computer feels. The CPU sets how quickly work is processed, and the amount of RAM sets how much can be open at once before the computer starts using the much slower storage drive as overflow. A hard disk drive is the slowest part of any computer that still has one.
Memory and storage are the pair most often confused. Memory is the desk you work on; storage is the filing cabinet. SSD vs HDD covers the two kinds of storage drive, and the storage library covers everything beyond a single drive.
MechanicsHow the components work together
What happens between pressing the power button and seeing the desktop shows how the parts of a computer depend on each other:
- Power. The power supply brings up its voltages and signals the motherboard that they are stable.
- Firmware. The processor starts executing the firmware stored on the motherboard, the BIOS or its successor UEFI.
- Self-test. The firmware runs the power-on self-test, checking the processor, memory and essential devices. A fault here produces beep codes or a blank screen.
- Boot device. The firmware finds the drive that holds the operating system and hands control to its boot loader.
- Operating system. The kernel loads from storage into memory, starts the drivers that talk to each piece of hardware, and then starts the desktop.
After that the pattern never changes: data is read from storage into memory, the processor works on it there, and the results are written back or sent to an output device.
The processor is fast, memory is slower, and storage is slower still, which is why adding memory or moving to an SSD often helps an old computer more than a faster processor would.
PeripheralsInput, output and peripheral devices
- Input devices send data to the computer: keyboard, mouse, touchscreen, scanner, microphone, webcam.
- Output devices present its results: monitor, printer, speakers, projector.
- Devices that do both: a touchscreen, a headset, a network adapter, an external drive.
Each one needs a driver, the software that lets the operating system talk to it. Many problems blamed on hardware are driver faults; how to reset a graphics driver covers the most common case.
ConnectionsPorts and connectors
- USB connects most peripherals and carries power. The connector shape, Type-A or Type-C, says nothing about the speed, which depends on the USB version behind it.
- Thunderbolt uses the USB Type-C connector and carries data, video and power at higher speeds, for docks and external drives.
- HDMI and DisplayPort carry video and audio to a monitor.
- Ethernet (RJ45) is the wired network port.
- Audio jacks carry analog sound.
- Inside the case, SATA connects drives, M.2 slots take NVMe SSDs, and PCIe slots take graphics and expansion cards.
FirmwareFirmware, BIOS and UEFI
Firmware is the part of hardware that can be updated like software, and the motherboard's firmware controls how the computer starts.
The older standard is BIOS; nearly everything made in the last decade uses UEFI, which supports larger drives, starts faster and can verify what it boots. UEFI vs BIOS compares them, and what ROM is explains the kind of memory firmware is stored in.
- Secure Boot is the UEFI feature that refuses to start a boot loader that is not signed by a trusted key. Windows 11 requires a computer that supports it; see how to enable Secure Boot. It depends on the drive using GPT, covered in MBR vs GPT.
- Firmware updates fix bugs and security flaws, and carry a small risk if interrupted. BIOS update covers when it is worth doing and how to do it safely.
- Settings and errors: a checksum error at startup usually means the firmware settings were lost, often because the small battery on the motherboard has died.
ServersServer hardware vs desktop hardware
A server has the same components as a desktop, built to run all day, every day, and to be repaired without being switched off.
| Desktop | Server | |
|---|---|---|
| Memory | Standard RAM | ECC memory, which detects and corrects single-bit errors |
| Power | One power supply | Two, redundant and hot-swappable |
| Storage | One or two drives | Many hot-swap drives behind a RAID controller |
| Management | Someone at the keyboard | A management controller that gives remote access even when the server is off |
| Form factor | Tower or small case | Rack mount, measured in rack units: 1U is 1.75 inches high |
Most servers today run a hypervisor and host many virtual servers; the virtualization library explains how. RAID 5 vs RAID 10 covers how their drives are arranged.
CablingNetwork cabling and structured wiring
The cabling in the walls is hardware too, and it outlives every device plugged into it.
- Twisted pair: the copper cable behind every Ethernet port. UTP cable explains its construction, and Cat6 vs Cat6a explains which category a new installation needs.
- Termination: the order of the eight wires in the connector follows one of two standards, compared in T568A vs T568B.
- Patch panels: the wall cables end at a patch panel in the rack, so that moves are made with short patch leads and not by re-terminating cable.
- Power over Ethernet: the same cable can power phones, cameras and access points, described on the 802.3af page.
DiagnosticsIdentifying and troubleshooting hardware
Before upgrading or replacing a part you need to know what is installed. How to check your motherboard model shows how to read it from the operating system without opening the case; the same tools report the processor, memory and drives.
Hardware troubleshooting works from the simplest cause to the least likely:
- Power and cables. Reseat them; a surprising share of faults end here.
- What changed. A new device, driver or update is the usual suspect.
- Signs and codes. Beep codes, diagnostic lights and the blue screen of death stop code point at the component.
- Heat. Dust and a failed fan cause throttling and shutdowns.
- Swap one part at a time with a known-good one, starting with memory and the power supply.
GlossaryHardware terms worth knowing
The computer hardware basics above rest on a handful of terms that appear on every specification sheet:
- Core and thread: a core is an independent processing unit inside the CPU; a thread is a sequence of instructions it can run, and many cores run two at once.
- Clock speed: how many cycles a core completes per second, in gigahertz.
- Chipset: the motherboard circuitry that links the processor to everything else and decides which parts are compatible.
- Form factor: the physical size and layout standard, such as ATX for motherboards or 2.5 inch for drives.
- Bus: a pathway that carries data between components, such as PCIe.
- Driver: the software that lets an operating system use a piece of hardware.
- Hot swap: replacing a component while the system keeps running.
