Module 1: Hardware and Operating Systems
Inside a Computer: Components and What They Do
When a user says "my computer is slow" or "it won't turn on", you need a mental picture of what is inside the box and how the parts work together. You do not need to be an electronics engineer, but you do need to know which component does what, how each one typically fails, and which symptoms point to which part. That knowledge lets you ask better questions, avoid replacing the wrong part, and explain problems clearly to users and managers.
The core components
| Component | What it does | Typical failure signs |
|---|---|---|
| CPU (processor) | Executes instructions; the "brain" | Overheating, shutdowns under load, very slow performance when fans are clogged |
| RAM (memory) | Short-term working space for running programs; cleared on power off | Slowness with many apps open, random crashes, blue screens, failure to start with beep codes |
| Storage (SSD or HDD) | Long-term storage for the operating system, programs and files | Very slow startup, clicking noises (HDD), files that will not open, "no boot device" errors |
| Motherboard | Connects all components and carries power and data between them | No power at all, ports not working, intermittent faults |
| Power supply / charger and battery | Converts mains power to the voltages components need | No power, shutdowns, laptop only works when plugged in, swollen battery |
| GPU (graphics) | Produces the display image; may be built into the CPU or a separate card | Screen artefacts, no display, crashes in video-heavy apps |
| Network adapter | Wired (Ethernet) or wireless (Wi-Fi) connection | Cannot see networks, frequent drops |
| Cooling (fans, heatsinks) | Removes heat from CPU, GPU and other parts | Loud fans, hot casing, thermal shutdowns |
How the parts work together
When you press the power button, the power supply sends power to the motherboard. The motherboard firmware (BIOS or, on modern machines, UEFI) runs a power-on self test (POST) to check basic hardware, then looks for a bootable storage device. It loads the operating system from storage into RAM, and the CPU starts running it. From then on, every program you open is loaded from storage into RAM, processed by the CPU, and shown through the GPU.
This sequence is useful in troubleshooting. If there are no lights or fans, think power. If there are lights but no display and beeps or flashing lights, think POST failure, often RAM or graphics. If you see the manufacturer logo and then a "no bootable device" message, think storage or boot order.
Key specifications to read
- Storage type and size: an SSD (solid state drive) is far faster than a traditional hard disk (HDD). Replacing an HDD with an SSD is often the single best upgrade for an older computer.
- RAM size: measured in gigabytes (GB). Check the operating system vendor's current recommendations and what the user's applications need, rather than relying on a fixed number.
- CPU model and generation: affects speed and which operating system versions are supported.
- Ports: USB-A, USB-C, HDMI, DisplayPort, Ethernet and audio. Knowing the ports helps when users need adapters for projectors or docks.
On Windows you can see the main specs in Settings > System > About, or by running msinfo32. On a Mac, use Apple menu > About This Mac.
Worked example: a laptop that will not start
A user at a Nairobi accounting firm brings in a laptop that "died" overnight. You follow the hardware sequence:
- Plug in a known-good charger. The charging light comes on, so power is reaching the laptop.
- Press power. Fans spin and the keyboard backlight comes on, but the screen stays black.
- Connect an external monitor via HDMI. The Windows login screen appears on the external monitor.
Conclusion: the laptop works; the problem is the built-in display or its cable, not the CPU, RAM or storage. You can now arrange a screen repair while the user carries on with an external monitor, instead of replacing the whole laptop.
Safety and good practice
- Shut down and unplug before opening any device; remove the battery if it is removable.
- Use an anti-static wrist strap or touch a grounded metal object before handling components.
- Never open a power supply unit; it can hold a dangerous charge.
- Stop using any swollen battery and dispose of it through a proper e-waste channel.
- Check the warranty before opening a device; opening it may void cover.
Common mistakes to avoid
- Assuming a black screen means a dead computer without testing an external display.
- Confusing storage with memory when talking to users ("my memory is full" usually means storage).
- Buying RAM or SSDs without checking compatibility with the exact model.
Exercise
On your own computer, find and write down the CPU model, RAM size, storage type and size, and the list of ports, using Settings or msinfo32 on Windows or About This Mac on macOS. Then write one sentence for each component describing a symptom a user might report if that part failed.
Key points
- Know what each component does and the symptoms of its failure.
- The boot sequence (power, POST, storage, operating system) helps you narrow down faults.
- An SSD upgrade is often the most effective improvement for an older computer.
- Work safely: power off, avoid static, never open power supplies, and check warranties.