In simple terms
A friendly intro before the formal notes — no formulas yet.
Designing Systems That Work for People
System design is the process of defining the parts and structure of a system to meet specific needs. Good design considers not just what the system does, but how easily and pleasantly people can use it.
Think about building a flat-pack wardrobe. The wooden panels, screws, and handles are the system's 'components' (hardware/software). The instruction booklet is the 'documentation'. How easy it is to follow the instructions, build the wardrobe, and then use it to store clothes is its 'usability'. A clear manual and well-made parts make for a highly usable wardrobe.
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First, identify the system's purpose and its core components, such as the hardware (e.g., CPU, RAM), software (e.g., OS, applications), and peripherals (e.g., printer, scanner).
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Next, evaluate the system's usability. Assess its effectiveness (does it achieve the goal?), efficiency (how quickly/easily?), and user satisfaction (is it a good experience?).
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Then, consider the documentation. Differentiate between user documentation (for the end-user) and technical documentation (for developers and maintainers).
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Finally, connect these elements. Explain how the choice of components and the quality of documentation directly impact the overall usability and success of the system.
Explore the concept
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Full topic notes
Formal explanation with the rigour you need for the exam.
Components of a Computer System
A computer system is more than just the box on your desk. It is an integrated set of components working together. For the IB syllabus, we must be able to identify and describe these parts.
Hardware: The physical parts of the computer you can touch. This includes internal components like the Central Processing Unit (CPU), Random Access Memory (RAM), and storage drives (SSD/HDD), as well as external ones.
Software: The set of instructions and programs that tell the hardware what to do. This is divided into system software (e.g., operating systems like Windows, macOS) and application software (e.g., word processors, web browsers).
Peripherals: External devices connected to the computer to add functionality. They are broadly categorised into input devices (keyboard, mouse, scanner), output devices (monitor, printer, speakers), and storage devices (external hard drive).
Human Component: The user who interacts with the system. Their needs, skills, and goals are the primary drivers for the system's design.
Usability
Usability is a measure of how easy a system is to use. It is not a single property but a combination of factors that contribute to the quality of a user's experience. A system with high usability is intuitive, efficient, and enjoyable to use, while one with low usability can cause frustration, errors, and abandonment. We evaluate usability using three key metrics.
Effectiveness: Can the user achieve their goal? For example, can a user successfully book a flight on a travel website? It's a binary measure of success or failure.
Efficiency: How much effort (time, clicks, mental energy) does it take to achieve the goal? A system where a task takes 3 clicks is more efficient than one where it takes 10 clicks.
Satisfaction: How does the user feel about their experience? This is a subjective measure, often gathered through surveys or feedback, concerning whether the interaction was pleasant, frustrating, or confusing.
In exam questions about usability, avoid vague statements like 'it's user-friendly'. You must explicitly use and apply the terms 'effectiveness', 'efficiency', and 'satisfaction'. Always justify your evaluation by referencing specific details from the scenario provided.
System Documentation
Documentation is any form of written or illustrated information that describes, explains, or instructs on a system. It is vital for both using and maintaining the system. There are two main categories of documentation, aimed at completely different audiences.
User Documentation: Aimed at the end-user. Its purpose is to teach someone how to use the software without needing to know the technical details. It includes user manuals, tutorials, help files, and FAQs. Good user documentation is clear, concise, and task-oriented.
Technical Documentation: Aimed at developers, programmers, and system administrators. Its purpose is to explain how the system was built and how it works internally. It includes information on the system architecture, data structures, algorithms, APIs, and code comments. This is essential for debugging, maintenance, and future development.
Worked examples
See the formulas applied — reveal one step at a time, like the exam.
A new automated ticketing system is installed at a train station. It consists of a touchscreen monitor, a credit card reader, a ticket-and-receipt printer, and a central server in a back office that runs the booking software and connects to the national rail network. A passenger uses the system to buy a ticket. Identify two hardware components, one software component, and one peripheral, explaining the role of each in this system. [4 marks]
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Here is a possible solution:
A company is deciding between two inventory management systems for its warehouse staff.
- System A is a modern tablet-based app with a graphical user interface (GUI). On average, staff take 30 seconds to locate and update an item's stock level. Most staff describe it as 'intuitive'.
- System B is an older system running on a terminal with a command-line interface (CLI). Experienced staff can update an item in 15 seconds using keyboard shortcuts, but new staff take over 2 minutes and make frequent errors. New staff report feeling 'stressed' when using it.
Evaluate the usability of System A compared to System B. [6 marks]
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Here is a model answer:
How it all connects
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Tap a linked idea to see how it connects back to the main topic — that connection is what examiners reward.
Glossary
Try to recall each definition before you reveal it.
Quick check
Answer in your head first — then tap to check. No pressure.
Revision flashcards
Flip the card. Test yourself before the exam.
What is a computer system?
A combination of hardware and software components that work together to process data and perform specific tasks.
Key takeaways
Review these before you close the topic — retrieval beats re-reading.
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Hardware: The physical parts of the computer you can touch. This includes internal components like the Central Processing Unit (CPU), Random Access Memory (RAM), and storage drives (SSD/HDD), as well as external ones.
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Software: The set of instructions and programs that tell the hardware what to do. This is divided into system software (e.g., operating systems like Windows, macOS) and application software (e.g., word processors, web browsers).
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Peripherals: External devices connected to the computer to add functionality. They are broadly categorised into input devices (keyboard, mouse, scanner), output devices (monitor, printer, speakers), and storage devices (external hard drive).
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Human Component: The user who interacts with the system. Their needs, skills, and goals are the primary drivers for the system's design.
Practice — then mark it
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Test your knowledge on System Design Basics
Test your knowledge on System Design Basics
Extra simulations & links
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Frequently asked
Checkpoint
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