Year 7 Digital Technologies · Digital Systems · 8m read

How Computers Work — Hardware and Software

Ever wondered why your phone slows down when you have too many apps open, or what actually happens when you click a button? Your computer is made of physical parts (hardware) like the processor and memory that work together with invisible instructions (software) like apps and operating systems to do everything you see on screen. Knowing how these pieces work together helps you troubleshoot problems, make smarter choices about devices, and understand the technology shaping your everyday world and future career options.

Learning objective: Describe the main components of a computer system and how hardware and software interact.

By the end of this lesson you can:

I name and describe CPU, RAM, storage, input and output devices.
I distinguish hardware from software.
I explain how the CPU processes data.

Computer system components

HARDWARE: physical components you can touch.
SOFTWARE: programs and operating systems (instructions for hardware).

HARDWARE COMPONENTS:

INPUT DEVICES: send data INTO the computer.
Keyboard, mouse, touchscreen, microphone, camera, scanner.

PROCESSING: the CPU (Central Processing Unit).
The "brain." Executes instructions. Speed measured in GHz (gigahertz).
Fetch → Decode → Execute → Store (the instruction cycle).

MEMORY:
RAM (Random Access Memory): fast, temporary. Holds data currently in use.
More RAM → more programs running at once.
Volatile: data lost when powered off.
ROM (Read Only Memory): permanent, small. Stores boot instructions.

STORAGE: permanent data storage.
HDD (Hard Disk Drive): magnetic, slower, cheaper, large capacity.
SSD (Solid State Drive): flash memory, faster, more durable, more expensive.
USB drives, DVDs, cloud storage.

OUTPUT DEVICES: send information OUT of the computer.
Monitor, printer, speakers, headphones.

OPERATING SYSTEM (OS): system software managing hardware and providing interface for applications.
Examples: Windows 11, macOS Ventura, Android, iOS, Linux.

Computer = human body analogy. CPU = brain (processes everything). RAM = short-term memory (what you're thinking right now). Storage = long-term memory (what you remember from years ago). Input devices = senses (eyes, ears). Output devices = actions (mouth, hands).

Key distinctions

RAM vs Storage: RAM is TEMPORARY (data gone when off). Storage is PERMANENT (data saved after shutdown). More RAM ≠ more storage.
Hardware vs Software: Hardware = physical. Software = instructions/code. Neither works without the other.
CPU speed vs RAM: Fast CPU + low RAM = bottleneck. The CPU waits for RAM. Both matter for performance.

Quick reference

| Component | Job |
|---|---|
| CPU | The "brain" — processes instructions |
| RAM | Short-term memory |
| Storage (SSD/HDD) | Long-term memory |
| Input devices | Keyboard, mouse, microphone |
| Output devices | Screen, speakers, printer |
| Software | Programs and operating system |

Worked example (Easy)

Your computer slows down when you open many programs at once, but still has plenty of storage space. Which component is likely the issue?

Analyse the symptom. Slow when many programs are open = too many things in current use at once.
Identify the component. RAM holds currently-running programs. If RAM is full, the OS uses slower storage as virtual memory → slowdown.
Conclusion. The issue is insufficient RAM, not storage.

Answer: Insufficient RAM is causing the slowdown.

Worked example (Hard)

A school needs computers for graphic design. Computer A: i5 CPU, 8 GB RAM, 256 GB SSD. Computer B: i7 CPU, 16 GB RAM, 1 TB HDD. Which is better and why?

Compare CPUs. i7 is faster than i5 — better for rendering and running demanding design software. Advantage: B.
Compare RAM. 16 GB (B) vs 8 GB (A). Graphic design software uses large amounts of RAM for editing. Advantage: B.
Compare storage. SSD (A) loads files much faster but 256 GB fills quickly with large image files. HDD (B) has more capacity but is slower.
Recommendation. Computer B is better overall (faster CPU, more RAM). Ideally upgrade its HDD to an SSD for faster file access.

Answer: Computer B (faster CPU, double the RAM) is better for graphic design, though an SSD upgrade would further improve it.

Common mistakes

Confusing RAM with storage Both store data but serve different purposes — students say "I need more RAM to save files." Fix: RAM = temporary workspace (lost when off). Storage = permanent filing cabinet. Running programs uses RAM; saving files uses storage.
Thinking a faster CPU alone fixes all slowness Performance depends on ALL components working together, not just the CPU. Fix: Identify the bottleneck: RAM (too many programs), storage (slow loading), or CPU (slow processing). The weakest component limits the system.

The fetch-decode-execute cycle and Moore's Law

Every instruction your CPU processes follows the same cycle: fetch the instruction from RAM, decode it to understand what operation is needed, execute the operation using the ALU, and store the result. This cycle repeats billions of times per second.

In 1965, Gordon Moore predicted that transistors on a chip would double approximately every two years — known as Moore's Law. The first Intel processor (1971) had 2,300 transistors; modern chips contain over 10 billion. More transistors means more calculations per second, enabling smartphones and AI.

However, Moore's Law is slowing as transistors approach atomic sizes. Engineers are exploring quantum computing, neuromorphic chips, and 3D chip stacking to continue improving performance. Understanding these physical limits helps explain why innovation in computer architecture remains one of technology's greatest challenges.

Practice questions

Which component is the PRIMARY processing unit of a computer?
1. RAM
2. SSD
3. CPU
4. GPU
(1 marks)
Explain the difference between RAM and storage with a real-world analogy.
(2 marks)

Summary

Name and describe CPU, RAM, storage, input and output devices.
Distinguish hardware from software.
Explain how the CPU processes data.