How a computer works: hardware, software & the boot process

Hardware vs software

Every computer is two things working together. Hardware is the physical equipment you can touch: the processor, memory, drives, screen, keyboard, and the board that links them. Software is the set of coded instructions that tells the hardware what to do — the operating system and the apps you run.

A useful way to remember it: hardware is the body, software is the thoughts and instructions. Neither is useful without the other. As a helpdesk technician, half your job is deciding whether a problem is hardware or software, so this distinction matters from day one.

The model behind every computer

No matter how big or small, a computer follows the same loop: input → process → output → storage.

• Input: data comes in (keyboard, mouse, microphone, network).
• Process: the CPU does the calculations and decisions.
• Output: results go out (screen, speakers, printer).
• Storage: data is kept for later (drive) or held briefly while in use (RAM).

A calculator, a phone, and a data-centre server all follow this exact pattern.

The four core components

Nearly every machine has four essentials:

• CPU (the processor) — does the actual work.
• RAM (memory) — fast, temporary workspace for whatever is running right now.
• Storage (HDD or SSD) — keeps your files when the power is off.
• Motherboard — the main board that connects everything, fed by the power supply.

We will open each of these up in later lessons. For now, just learn the names.

The boot process, step by step

When you press the power button, a precise sequence runs:

1. Power flows from the power supply to the motherboard.
2. The motherboard firmware (BIOS on older PCs, UEFI on modern ones) starts first.
3. Firmware runs POST (Power-On Self-Test) to confirm RAM, CPU and other essentials are present and healthy.
4. Firmware finds the boot device (usually the main drive) and loads the bootloader.
5. The bootloader starts the operating system.
6. The OS loads drivers and shows you the login screen and desktop.

If POST fails, you may hear beep codes or see an error before any OS appears — a strong clue the problem is hardware.

BIOS/UEFI and the operating system

Think of firmware as the building’s caretaker who unlocks the doors and checks the lights work, then hands the keys to the operating system — the manager who actually runs the place. You can usually enter firmware settings by tapping a key like Del, F2, or F10 right after powering on.

You can confirm key system facts from inside Windows once it boots:

systeminfo | findstr /B /C:"OS Name" /C:"System Type" /C:"BIOS Version"

Your task

Watch a computer boot and narrate the stages out loud. Power on a PC and tap the firmware key (often Del or F2) to peek at the BIOS/UEFI screen, then exit without changing anything. Once Windows loads, open PowerShell, run the systeminfo command above, and write down the OS name, system type, and BIOS version. In two sentences, describe what happened between pressing power and seeing the desktop.