IGCSE Computer Science (0478) · Paper 1 — Computer Systems
Hardware
The fetch–decode–execute cycle and register roles (PC, MAR, MDR, CIR, Accumulator) are the most commonly mis-sequenced answers on this topic — examiners mark the order of operations, not just the register names.
3.1 Computer architecture
- Understand the role of the central processing unit (CPU) in a computer.
- Understand what is meant by a microprocessor.
- Understand the purpose of the components in a CPU in a computer with Von Neumann architecture: units (ALU, CU), registers (PC, MAR, MDR, CIR, ACC) and buses (address, data, control).
- Describe the process of the fetch-decode-execute (FDE) cycle, including the role of each component in the process.
- Understand what is meant by a core, cache and clock in a CPU and explain how they can affect the performance of a CPU.
- Understand the purpose and use of an instruction set for a CPU.
- Describe the purpose and characteristics of an embedded system and identify devices in which they are commonly used (e.g. domestic appliances, cars, vending machines), distinguishing from a general purpose computer.
3.2 Input and output devices
- Understand what is meant by an input device and why it is required, including barcode scanner, digital camera, keyboard, microphone, optical mouse, QR code scanner, touch screen and 2D/3D scanners.
- Understand what is meant by an output device and why it is required, including actuator, DLP/LCD projector, inkjet/laser printer, LED/LCD screen, speaker and 3D printer.
- Understand what is meant by a sensor and the purposes of sensors, limited to acoustic, accelerometer, flow, gas, humidity, infra-red, level, light, magnetic field, moisture, pH, pressure, proximity and temperature.
- Identify the type of data captured by each sensor and understand when each sensor would be used, including selecting the most suitable sensor for a given context.
3.3 Data storage
- Understand what is meant by primary storage, including the role of RAM and ROM and why a computer needs both.
- Understand what is meant by secondary storage and why it is necessary for more permanent storage of data.
- Describe the operation of magnetic (HDD), optical (CD, DVD, Blu-ray) and solid-state (SSD, SD card, USB drive) storage and give examples of each.
- Describe what is meant by virtual memory, how it is created and used (pages transferred between RAM and virtual memory) and why it is necessary.
- Understand what is meant by cloud storage, accessed remotely versus storing data locally.
- Explain the advantages and disadvantages of storing data on the cloud in comparison to storing it locally.
3.4 Network hardware
- Understand that a computer needs a network interface card (NIC) to access a network.
- Understand what is meant by, and the purpose of, a media access control (MAC) address, including its structure (manufacturer code + serial code, written as hexadecimal).
- Understand what is meant by, and the purpose of, an internet protocol (IP) address, allocated by the network as static or dynamic.
- Understand that there are different types of IP address, including the characteristics of, and differences between, IPv4 and IPv6.
- Describe the role of a router in a network: sending data to a specific destination, assigning IP addresses, connecting a local network to the internet.
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