Computer architecture
Cambridge IGCSE Computer Science (0478) · Unit 3: Hardware · 10 flashcards
Computer architecture is topic 3.1 in the Cambridge IGCSE Computer Science (0478) syllabus , positioned in Unit 3 — Hardware , alongside Input and output devices, Memory and storage and Logic gates. In one line: The CPU (Central Processing Unit) is the brain of the computer. It executes instructions in a program by performing calculations, making logical decisions, and controlling the other components of the system.
This topic is examined in Paper 1 (computer systems theory) and Paper 2 (algorithms, programming and logic).
The deck below contains 10 flashcards — 7 definitions and 3 key concepts — covering the precise wording mark schemes reward. Use the 7 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.
The term 'CPU' and describe its main function
The CPU (Central Processing Unit) is the brain of the computer. It executes instructions in a program by performing calculations, making logical decisions, and controlling the other components of the system.
What the Cambridge 0478 syllabus says
Official 2026-2028 specThese are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.
- Understand Understand the role of the central processing unit (CPU) in a computer
- Understand Understand what is meant by a microprocessor
- Understand Understand the purpose of the components in a CPU in a Von Neumann architecture including ALU, control unit, registers (PC, MAR, MDR, CIR, accumulator), and buses (address, data, control)
- Describe Describe the process of the fetch-decode-execute (FDE) cycle including the role of each component
- Understand 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 Understand the purpose and use of an instruction set for a CPU
- Describe Describe the purpose and characteristics of an embedded system and identify devices in which they are commonly used
Define the term 'CPU' and describe its main function.
The CPU (Central Processing Unit) is the brain of the computer. It executes instructions in a program by performing calculations, making logical decisions, and controlling the other components of the system.
What are the three main components of the CPU, and what is the role of each?
The three main components are the ALU (Arithmetic Logic Unit), the Control Unit, and Registers. The ALU performs calculations and logical operations. The Control Unit manages the execution of instructions. Registers are small, high-speed storage locations used to hold data and instructions.
Explain the purpose of the Program Counter (PC) and how it is used in the fetch-decode-execute cycle.
The Program Counter holds the address of the next instruction to be executed. During the fetch stage, the address in the PC is used to retrieve the instruction from memory, and then the PC is incremented to point to the subsequent instruction.
Describe the functions of the Memory Address Register (MAR) and the Memory Data Register (MDR).
The MAR holds the address of the memory location being accessed. The MDR holds the data being transferred to or from that memory location, acting as a buffer between the CPU and memory.
What is the role of the Current Instruction Register (CIR) in the fetch-decode-execute cycle?
The CIR holds the instruction that is currently being decoded and executed. After the instruction is fetched from memory, it's stored in the CIR for further processing by the Control Unit.
Explain the difference between the address bus, the data bus, and the control bus.
The address bus carries the memory address from the CPU to memory. The data bus carries the actual data being transferred. The control bus carries control signals (
Describe the fetch-decode-execute cycle, outlining the steps involved in processing an instruction.
The fetch-decode-execute cycle is the fundamental operation of a CPU. It involves fetching an instruction from memory, decoding the instruction to determine what operation to perform, and then executing the instruction.
Explain how clock speed affects the performance of a CPU.
Clock speed, measured in Hertz (Hz), determines the rate at which a CPU can execute instructions. A higher clock speed generally means faster processing, as the CPU can complete more cycles per second.
Describe the purpose of cache memory and explain how it improves performance.
Cache memory is a small, fast memory located closer to the CPU than main memory. It stores frequently accessed data and instructions, allowing the CPU to retrieve them more quickly, thereby reducing access time and improving performance.
What is a 'core' in the context of CPUs, and how does having multiple cores benefit performance?
A core is an independent processing unit within a CPU. Multiple cores allow a CPU to execute multiple tasks simultaneously, improving performance for multi-threaded applications and multitasking.
Key Questions: Computer architecture
Define the term 'CPU' and describe its main function.
The CPU (Central Processing Unit) is the brain of the computer. It executes instructions in a program by performing calculations, making logical decisions, and controlling the other components of the system.
Explain the purpose of the Program Counter (PC) and how it is used in the fetch-decode-execute cycle.
The Program Counter holds the address of the next instruction to be executed. During the fetch stage, the address in the PC is used to retrieve the instruction from memory, and then the PC is incremented to point to the subsequent instruction.
Describe the functions of the Memory Address Register (MAR) and the Memory Data Register (MDR).
The MAR holds the address of the memory location being accessed. The MDR holds the data being transferred to or from that memory location, acting as a buffer between the CPU and memory.
What is the role of the Current Instruction Register (CIR) in the fetch-decode-execute cycle?
The CIR holds the instruction that is currently being decoded and executed. After the instruction is fetched from memory, it's stored in the CIR for further processing by the Control Unit.
Explain the difference between the address bus, the data bus, and the control bus.
The address bus carries the memory address from the CPU to memory. The data bus carries the actual data being transferred. The control bus carries control signals (
More topics in Unit 3 — Hardware
Computer architecture sits alongside these Computer Science decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 0478 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Key terms covered in this Computer architecture deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
How to study this Computer architecture deck
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