Computer Systems Exam Practice
This lesson provides exam-style questions and model answers covering the entire Computer Systems topic. Use this to consolidate your knowledge and practise the types of questions you will face in your AQA or OCR GCSE Computer Science exam.
Exam Technique
Before attempting the questions, remember these key principles:
| Principle | Detail |
|---|
| Read the question carefully | Identify the command word (define, describe, explain, compare, evaluate) |
| Use technical vocabulary | The mark scheme rewards precise, subject-specific language |
| Answer for the marks available | A 2-mark question needs two distinct points; a 4-mark question needs four |
| Show your working | For calculation questions, show each step — you may get marks even if the final answer is wrong |
| Use examples | Where appropriate, give a specific example to support your answer |
Command Words
| Command Word | What It Means |
|---|
| Define | Give the precise meaning of a term |
| State | Give a brief, factual answer |
| Describe | Set out the main features or characteristics |
| Explain | Give reasons or say how/why something happens |
| Compare | Identify similarities and/or differences |
| Evaluate | Weigh up the pros and cons; give a justified conclusion |
Topic Map
The Computer Systems topic links together hardware, systems software and applications. The diagram below shows how the major concepts interconnect.
graph TD
A["Computer Systems"] --> B["Hardware"]
A --> C["Software"]
B --> D["CPU (ALU, CU, Registers)"]
B --> E["Primary Memory (RAM, ROM)"]
B --> F["Secondary Storage"]
C --> G["Systems Software"]
C --> H["Application Software"]
G --> I["Operating System"]
G --> J["Utility Software"]
D --> K["Fetch-Decode-Execute Cycle"]
Practice Questions
Question 1 (2 marks)
Define the term "volatile memory" and give one example.
Model Answer:
- Volatile memory is memory that loses its contents when the power is switched off (1 mark).
- Example: RAM (1 mark).
Question 2 (3 marks)
Describe the roles of three registers used in the fetch-decode-execute cycle.
Model Answer:
- The Program Counter (PC) holds the memory address of the next instruction to be fetched (1 mark).
- The Memory Address Register (MAR) holds the address of the memory location currently being read from or written to (1 mark).
- The Memory Data Register (MDR) holds the data that has just been fetched from memory or the data that is about to be written to memory (1 mark).
Question 3 (4 marks)
Explain two factors that affect CPU performance.
Model Answer:
- Clock speed: A higher clock speed means the CPU completes more fetch-decode-execute cycles per second (1 mark), so more instructions are processed in a given time, improving performance (1 mark).
- Number of cores: More cores allow the CPU to process multiple instructions simultaneously through parallel processing (1 mark), which improves performance for software that is designed to use multiple cores (1 mark).
Question 4 (2 marks)
State two differences between RAM and ROM.
Model Answer:
- RAM is volatile (loses data when power is off); ROM is non-volatile (retains data when power is off) (1 mark).
- RAM is read and write (data can be changed); ROM is read-only (data cannot normally be changed by the user) (1 mark).
Question 5 (4 marks)
Compare magnetic storage (HDD) and solid-state storage (SSD). Give two advantages and two disadvantages of SSDs compared to HDDs.
Model Answer:
- Advantage 1: SSDs are much faster than HDDs because they have no moving parts and access data electronically rather than mechanically (1 mark).
- Advantage 2: SSDs are more durable because they have no moving parts, making them resistant to shock and vibration (1 mark).
- Disadvantage 1: SSDs have a higher cost per gigabyte than HDDs, so they are more expensive for the same storage capacity (1 mark).
- Disadvantage 2: SSDs generally have lower maximum capacity than HDDs at the same price point (1 mark).
Question 6 (6 marks)
Describe three functions of an operating system.
Model Answer:
- Memory management: The OS allocates RAM to running programs and deallocates it when programs close (1 mark). It also manages virtual memory when RAM is full, using part of secondary storage as overflow (1 mark).
- File management: The OS provides a file system to organise files into folders and directories (1 mark). It controls file naming, permissions, copying, moving, and deleting (1 mark).
- Peripheral management: The OS manages input and output devices using device drivers (1 mark). Device drivers translate between the OS and the specific hardware, allowing the computer to use printers, keyboards, and other devices (1 mark).
Question 7 (2 marks)
What is an embedded system? Give one example.
Model Answer:
- An embedded system is a computer system built into a larger device that is dedicated to performing a specific function (1 mark).
- Example: The control system in a washing machine (which controls the wash cycle, temperature, and spin speed) (1 mark).
Question 8 (4 marks)
Give two differences between an embedded system and a general-purpose computer system.
Model Answer:
- An embedded system is designed for a single, dedicated task (e.g., controlling a washing machine), whereas a general-purpose system can perform many different tasks and run a variety of software (1 mark for each, 2 marks total).
- An embedded system usually has a very limited or no user interface (e.g., buttons and LEDs), whereas a general-purpose system has a full user interface (screen, keyboard, mouse) (1 mark for each, 2 marks total).
Question 9 (3 marks)
Explain the difference between a compiler and an interpreter.
Model Answer:
- A compiler translates the entire program into machine code in one go, producing a standalone executable file (1 mark).
- An interpreter translates and executes the program one line at a time, without producing a separate executable file (1 mark).
- Compiled programs run faster because the translation has already been done; interpreted programs are slower because translation occurs at runtime (1 mark).
Question 10 (4 marks)
A school is buying new computers. Explain why adding more RAM would improve performance, and why having an SSD instead of an HDD would also help.