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How Do Computers Work? A Beginner’s Guide to Hardware

Photo by Christian Wiediger on Unsplash

Computers are ubiquitous in our modern society. We use desktops and laptops to do our daily work, and mobile devices to connect, communicate, and be entertained in our downtime. But how do computers work? This guide to hardware is a primer on the internal workings of modern computers and mobile devices.

What is the Difference Between Hardware and Software?

Hardware components are the physical components of a machine. For example, a laptop’s hard disk drive, a phone’s camera, and a USB mouse are all pieces of hardware. A computer is hardware.

This is generally opposed to software. Software is a series of digital instructions and data designed to carry out the functionality of a program. An app or a game is software.

Less commonly mentioned is firmware, which is technically software but is embedded into hardware devices to control their operation.

Hardware Components of a Computer

Let’s take a look at the different components that make up the hardware of a computer device.


The motherboard is a circuit board that connects all of the other components of a computer. When building your own computer, choosing the right motherboard for the build is important, as this choice dictates what compatible parts you will be able to use for the rest of the computer.

Motherboards come in different shapes and sizes. These are called form factors.

A motherboard usually contains slots for CPUs, RAM, interfaces for storage (like SATA ports for hard disk drives and solid-state drives), expansion slots (such as PCIe slots), and peripheral connectors (USB ports, audio jacks, video output ports, etc.).

Motherboards also contain chipsets to manage communication between all of the attached components.

Embedded in the motherboard is the BIOS/UEFI firmware that initializes hardware when the computer is turned on and provides configuration options to users.

Central Processing Unit (CPU)

Central processing units (CPUs) carry out arithmetic and logic operations, manipulate data, control the flow of programs, and handle input/output operations, among other things. They are like the brain of a computer.

CPUs contain: a control unit to manage the flow of data and the execution of instructions; an arithmetic logic unit (ALU) to perform arithmetic and logic operations; registers, high speed memory for storing data and instructions being used by the CPU.

CPUs get very hot, so there are usually cooling systems such air or liquid cooling in computers to draw away and dissipate heat from the CPU.

Modern CPUs can have multiple cores and threads. This is parallel processing and using it is essentially like running multiple CPUs at the same time, each able to carry out their instructions in parallel. This improves the performance and multi-tasking capabilities of a computer.

Primary Storage

Primary storage (also known as main memory or primary memory) is storage that is directly accessible by the CPU. It is used to store the data and instructions that the CPU is working with.

Primary storage is volatile memory. If you reset your computer or device, volatile memory is wiped clean.

The two main examples of primary storage are cache memory and RAM.

Cache Memory

Cache memories are small and extremely fast. They are located close to the CPU and store the data and instructions most frequently used by the CPU.

Modern computers have multiple levels of caches. L1 caches are closest to the CPU and are fastest but smallest. L2 and L3 are progressively slower and farther from the CPU.

Random Access Memory (RAM)

RAM is slower than cache memory but can store much more data.

RAM is measured in bits and bytes. In computers and laptops, it comes in the form of RAM sticks (chips that are inserted in matching pairs into the RAM slots of a motherboard).

The size and complexity of the programs you can run on your computer, and your computer’s speed when executing programs, are both highly dependent on the holy trinity of your motherboard, your CPU, and your RAM.

Secondary Storage

Secondary storage is also known as auxiliary storage or external memory. It is non-volatile memory (it retains data even when the computer is switched off) and because of that it is used for long-term storage of data and programs.

There are many forms of secondary storage, including hard disk drives (HDDs), solid-state drives (SSDs), optical disks (CDs, DVDs, Blu-rays), and flash memory (phones and USB drives). Modern computers most commonly have hard disk drives or solid-state drives for secondary storage. Many portable devices use flash memory.


A bus is a communication channel that allows components to transmit data between each other. Motherboards have buses for communication between components, such as the CPU and the cache, the CPU and the RAM, or the CPU and peripheral devices.

Different buses have different widths and speeds. The width determines how much data may be transferred at once while the speed determines how quickly it is transferred. More efficient buses are used for higher priority connections, such as the CPU to the primary storage.


A display is generally a screen connected to the motherboard through a port in a graphics card or a direct connection to the motherboard itself. Display types range from LCD calculators to mobile phone screens to ultra-high-definition televisions and monitors.

Touch displays can allow for user input through tapping, gestures, or a stylus.


Many devices have in-built speakers. Some desktops require external speakers that plug into the motherboard or a sound card expansion.


Most computer and laptop motherboards come with expansion slots that allow the addition of expansion cards such as graphics cards, network interface cards, and sound cards.

Graphics Cards

If you want to play anything with system-intensive graphics, then you need a graphics card. Graphics cards have specialized CPUs called Graphics Processing Units (GPUs) and their own primary storage to facilitate the efficient calculation and rendering of graphics to the display. Some graphics cards allow for multiple displays through standards such as HDMI, DisplayPort, and USB-C.

Most computers come with onboard graphics, but onboard graphics are not nearly as powerful as graphics card expansions.

If you want to play games, you need a good graphics card. If you want to play modern games, you need a modern graphics card. Graphics cards are also useful for other purposes, such as video editing or streaming to video platforms such as Twitch or YouTube.

Network Interface Cards (NICs)

Every device that connects to a network such as the Internet requires a network interface. Network interface cards can connect to networks through wired Ethernet connections, Wi-Fi, or both. They prepare, transmit, and receive data over networks using various communication protocols.


Various peripherals can be connected to motherboards, including USB ports and therefore anything that connects via USB. Audio jacks, video output ports, cameras, and other peripherals can be connected or incorporated into computers and devices. Wireless technology expands the range of peripherals even further.

Power Supply

The power supply provides power to the computer or device’s motherboard and components. Some components are powered through the motherboard while others might require wiring directly to the power supply.

Laptops and mobile devices use rechargeable batteries to allow for portability. Many desktops have no such battery system: they contain large power supplies that must be plugged directly into a wall socket or other power source in order to turn on and remain on.


We have covered the broad strokes of the essential hardware components in a modern computer:

  • Motherboard
  • Central Processing Unit (CPU)
  • Primary storage
  • Secondary storage
  • Buses
  • Display
  • Audio
  • Expansions
  • Peripherals
  • Power supply

Leave a comment on this blog article telling me whether you want to read more in-depth guides to computer hardware in the future, what you thought of this article, or any other thoughts you may have.

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I wish you all the best in your journey of learning and discovery.

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