O Level Computer Science: Hardware (Cambridge 2210)

Topic 3 Hardware sits in the “Computer systems” half of Cambridge O Level Computer Science (2210), examined on Paper 1. Cambridge builds 2210 on the same content as Cambridge IGCSE Computer Science (0478) – the two share identical topic names, order and subject content, so teachers using IGCSE-endorsed textbooks can use them directly with this O Level too. This guide covers Topic 3 in full: computer architecture, input and output devices, data storage, and network hardware.

3.1 Computer architecture – the fetch-decode-execute cycle

Start with the CPU’s job: it processes the instructions and data that are input into the computer so that a result can be output. A microprocessor is a type of integrated circuit that packages this processing capability onto a single chip.

For a computer built on Von Neumann architecture, you need to know three families of internal component and how they interact during the fetch-decode-execute (FDE) cycle:

Category	Components
Units	Arithmetic logic unit (ALU), control unit (CU)
Registers	Program counter (PC), memory address register (MAR), memory data register (MDR), current instruction register (CIR), accumulator (ACC)
Buses	Address bus, data bus, control bus

The FDE cycle fetches instructions and data from RAM into the CPU, stores them in the appropriate registers, transmits data, addresses and signals along the buses, and uses the ALU and CU to fetch, decode and execute each instruction in turn.

Beyond the cycle itself, examiners can ask about cores, cache and clock speed and how each affects CPU performance (more cores, a larger cache and a higher clock speed can all improve it), the instruction set (the fixed list of machine-code commands a CPU can process), and embedded systems – devices built to perform one dedicated function (domestic appliances, cars, security systems, lighting systems, vending machines), in contrast to a general-purpose computer such as a PC or laptop that runs many different applications.

3.2 Input and output devices – know the list, know the context

This sub-topic rewards precise recall of named devices over general familiarity, since Cambridge limits examinable devices to specific lists:

Input: barcode scanner, digital camera, keyboard, microphone, optical mouse, QR code scanner, touch screen (resistive, capacitive, infra-red), 2D and 3D scanners.

Output: actuator, digital light processing (DLP) projector, inkjet printer, laser printer, LED screen, LCD projector, LCD screen, speaker, 3D printer.

Sensors, examined separately, are limited to: acoustic, accelerometer, flow, gas, humidity, infra-red, level, light, magnetic field, moisture, pH, pressure, proximity and temperature. You need to understand what a sensor is and its purpose, then identify what data each named sensor captures and select the most suitable sensor for a given context – for example, a moisture sensor in an automated plant watering system, or a pH sensor in a swimming pool monitoring system. Scenario questions on this sub-topic are answered well by matching the sensor to what it physically measures, not by guessing from the sensor’s name alone.

3.3 Data storage

Three storage categories are distinguished here.

Primary storage is accessed directly by the CPU: RAM (volatile, holds data and instructions currently in use) and ROM (non-volatile, typically holds startup instructions). Know why a computer needs both and what separates them.

Secondary storage is not directly accessed by the CPU and provides more permanent storage:

Technology	How it works	Examples
Magnetic	Platters divided into tracks and sectors; read/written using electromagnets	Hard disk drive (HDD)
Optical	Lasers create and read pits and lands	CD, DVD, Blu-ray
Solid-state (flash)	NAND/NOR technology; transistors as control and floating gates	SSD, SD card, USB drive

Virtual memory describes how pages of data are transferred between RAM and virtual memory when needed, and why this is necessary when physical RAM is insufficient. Cloud storage is assessed for both its advantages (remote access from any location) and disadvantages (dependence on physical servers and storage hosted elsewhere, compared with the direct control of storing data locally).

3.4 Network hardware

The final sub-topic covers what a device needs to join and be identified on a network:

• A network interface card (NIC) is required to access a network.
• Every NIC carries a MAC address, assigned at manufacture, built from a manufacturer code and a serial code, and usually written in hexadecimal.
• An IP address is allocated by the network itself and can be static or dynamic; know the characteristics of, and differences between, IPv4 and IPv6.
• A router directs data to a specific destination on a network, can assign IP addresses, and connects a local network to the internet.

This sub-topic builds directly on Topic 2 (Data transmission): a router’s role in directing packets connects straight back to the packet-switching content there, so revise the two together.

How to approach it

Computer architecture is the single hardest sub-topic to hold in memory reliably, so practise tracing one instruction through the full FDE cycle by hand, naming which register or bus is active at each step, rather than trying to memorise the component list as isolated facts. For 3.2, make yourself a sensor-to-application table and test yourself against unfamiliar scenarios, since exam questions reward matching a sensor to what it measures rather than recognising its name. Across 3.3 and 3.4, the syllabus repeatedly asks for explicit comparisons – RAM vs ROM, primary vs secondary storage, local vs cloud storage, IPv4 vs IPv6 – so practise writing short, structured “difference between” answers for each pair rather than treating them as separate topics to learn independently.

Official syllabus

Cambridge International, Cambridge O Level Computer Science (2210) syllabus for examination in 2026, 2027 and 2028 (Version current as of December 2025): official syllabus PDF, Subject content, section 3 “Hardware”. Verified 2026-09-02 – content confirmed identical to the equivalent Cambridge IGCSE Computer Science (0478) section, consistent with Cambridge’s own statement that this O Level shares its subject content with 0478.