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IB DP Computer Science Study Notes

1.2.6 Usability in System Design

Understanding and implementing usability in system design is critical in creating technology that is not only functional but also user-friendly and accessible. This section examines the intricacies of usability, focusing on the relationship between ergonomics, accessibility, and user satisfaction. Additionally, it identifies common usability problems in various digital devices and systems, and suggests methods to enhance user interaction and experience.

Defining Usability

Usability in system design is essential for ensuring that users can interact with a system effectively, efficiently, and satisfactorily to accomplish their goals. Key factors of usability include:

  • Ease of Learning: How straightforward is it for users to accomplish basic tasks the first time they encounter the design?
  • Efficiency of Use: Once familiar with the design, how quickly can users perform tasks?
  • Memorability: If users return to the design after a period of not using it, how easily can they reestablish proficiency?
  • Error Frequency and Severity: How often do users make errors, how serious are these errors, and how do they recover from them?
  • Subjective Satisfaction: How pleasant is it to use the design?

Ergonomics and Accessibility

  • Ergonomics: This aspect focuses on the logical, comfortable layout of interactive elements and physical ease of use, aiming to reduce user fatigue and discomfort. It considers factors such as screen placement, keyboard spacing, and mouse sensitivity.
  • Accessibility: Concerned with creating systems that are usable for people of all abilities and disabilities. This includes designing for various impairments like visual, auditory, motor, and cognitive challenges. The goal is to create systems that are not only usable but also equitable and inclusive.

Usability Problems in Digital Devices

Usability problems can vary significantly across different types of digital devices:


  • Complex User Interfaces: Often, PC software features cluttered interfaces with too many options, overwhelming users, especially beginners.
  • Inconsistent User Experience: Variations in software layouts and operating procedures can cause confusion and increase the learning curve.

Digital Cameras

  • Small Physical Controls: Can be difficult to manipulate, particularly for users with motor impairments or larger hands.
  • Complex Menu Systems: Extensive, multi-level menus can be confusing, making it hard to find specific settings or options.

Mobile Phones

  • Screen Size Constraints: Especially in older models, small screens can impede usability, affecting the visibility of content and the ease of touching controls accurately.
  • Touchscreen Accuracy: Users with motor difficulties or larger fingers may struggle with precise interactions, such as typing or selecting small on-screen items.

Games Consoles

  • Controller Design: Controllers that are not ergonomically designed can cause hand and wrist strain during extended use.
  • Interface Complexity: Non-intuitive interfaces can hinder non-gamers or beginners from fully enjoying the gaming experience.

MP3 Players

  • Interface Navigation: Small buttons and screens can make navigation and selection tasks challenging.
  • Physical Interaction: Limited physical feedback can hinder the user's ability to operate the device without looking directly at it.

Improving System Accessibility

To address these challenges, several strategies can be employed:

  • Touchscreen Technology: Offers a direct and intuitive way of interaction that can be easier for users with motor difficulties who find traditional input devices like mice or keyboards challenging.
  • Voice Recognition: Enables hands-free control and assists users with visual impairments or motor restrictions. It allows users to interact with devices through spoken commands.
  • Text-to-Speech (TTS): Particularly beneficial for users with visual impairments, TTS technology converts on-screen text into speech, enabling these users to receive the same information as sighted users.
  • Braille Keyboards and Displays: Essential for users who are blind, allowing them to input and read text through tactile means.

Usability Problems in Systems

System design often overlooks potential usability problems, impacting user efficiency and satisfaction:

Ticketing Systems

  • Complex Processes: Users often face difficulty understanding multiple steps or navigating through convoluted booking processes.
  • Screen Readability: Small font sizes and poor contrast in user interfaces can make reading and selection tasks difficult, especially on mobile platforms.

Online Payroll Systems

  • Jargon and Complexity: Payroll systems filled with professional jargon or complex navigation can be daunting for the average user, leading to errors or underutilisation.
  • Consistency and Familiarity: Lack of consistency with common software paradigms can confuse users. Familiar layouts and terminology can improve usability significantly.

Scheduling Systems

  • Interface Overload: Overwhelming amounts of data or features packed into a single screen can confuse users.
  • Adaptability: Systems that fail to cater to various user working styles or preferences can limit efficiency and satisfaction.

Voice Recognition Systems

  • Accents and Speech Variations: Systems often have difficulty accurately interpreting accents, dialects, and individual speech patterns, leading to errors or non-compliance.
  • Environmental Factors: Background noise and poor microphone quality can significantly affect the system's ability to understand commands correctly.

Feedback-Providing Systems

  • Response Timing: Systems that provide delayed feedback can frustrate users, who expect prompt reactions to their inputs.
  • Clarity and Helpfulness: Feedback that is vague, overly technical, or unhelpful can lead to user dissatisfaction and a feeling of being unsupported.

Overall, usability in system design is a multifaceted discipline that plays a crucial role in the effectiveness and success of a digital product or system. By prioritising user-centred design, considering ergonomic and accessibility factors, and regularly testing with real users, designers and developers can significantly improve the usability of their products. This not only enhances the user experience but also contributes to the broader accessibility and inclusiveness of digital technologies.


Feedback in user interfaces is vital for communicating the system's status and responses to the user's actions, enhancing the overall usability. Immediate and clear feedback, such as visual cues or audio signals after a user interaction, confirms that the system is processing the user's request. For example, highlighting a button when it's clicked or providing a loading animation during data processing helps users understand that their input has been received and the system is working as expected. This kind of feedback is particularly important in preventing users from repeating inputs unnecessarily, reducing the chances of errors, and improving user confidence and satisfaction. Inadequate or delayed feedback can lead to confusion, making the interface feel unresponsive and less intuitive.

Animations in a system can both enhance and hinder usability, depending on their implementation. When used effectively, animations can make interfaces more intuitive and engaging. They can guide users' attention to important elements, demonstrate how to interact with certain features, and provide satisfying and informative feedback on actions taken. However, excessive or poorly executed animations can distract users, slow down interactions, and potentially cause confusion or annoyance. For users with certain cognitive disabilities or motion sensitivity, these animations can be disorientating or even physically uncomfortable. Therefore, it's crucial to use animations purposefully and sparingly, with an option for users to reduce or disable them, ensuring that the system remains accessible and comfortable for all users.

The layout of a user interface is fundamental to its usability. An intuitive and well-organized layout allows users to navigate and interact with the system efficiently. Key elements should be easily accessible and arranged logically, following natural reading patterns (left to right, top to bottom in most Western cultures). Consistency in the layout across different parts of the system also aids in user familiarity and reduces the learning curve. Grouping related items together and ensuring sufficient spacing can prevent user errors and cognitive overload. Poor layout designs, such as those with overcrowded screens, hidden essential functions, or inconsistent navigation paths, can lead to user frustration, increased errors, and ultimately, a decrease in system efficacy and user satisfaction.

Considering different age groups in user interface design is crucial due to varying needs, abilities, and technology familiarity. Younger users might prefer fast-paced, visually rich interfaces with interactive elements, while older users often benefit from simpler, clearer, and more consistent designs with larger text and clickable areas. To accommodate these differences, designers can implement adaptable user interfaces with customisation options like adjustable text sizes and contrast settings. Including various difficulty levels or tutorial modes can cater to differing levels of tech-savviness and cognitive abilities. By designing with a broad user demographic in mind, a system can become more inclusive, reaching a wider audience and ensuring a better user experience for all age groups.

Colour schemes play a crucial role in interface design, significantly impacting usability. A well-chosen colour scheme can enhance readability, draw attention to key elements, and create an intuitive experience. For instance, high contrast between text and background improves readability, especially for users with visual impairments like colour blindness or reduced vision. It's vital to avoid colour combinations that are difficult for colour-blind users to distinguish (such as red/green). Moreover, using colours consistently across an interface can help in indicating similar types of content or actions, aiding users in quickly navigating the interface. However, overuse or poor choice of colours can lead to user confusion, eye strain, and a general decrease in the system's usability.

Practice Questions

Describe two usability problems that might be encountered in mobile phone interfaces and suggest one improvement for each.

A notable usability problem in mobile phone interfaces is the challenge of navigating through complex menu systems. These systems can be particularly daunting for older users or those not familiar with advanced technology. An improvement could be the simplification of menus, consolidating related functions, and employing a more intuitive graphical layout to facilitate ease of use. Another common issue is the small touchscreen keyboard, which can be problematic for users with larger fingers or motor impairments. To improve this, predictive text and voice-to-text features can be integrated, enabling users to input text more comfortably and accurately.

Explain how voice recognition technology can enhance the usability of digital devices for users with disabilities. Provide one example.

Voice recognition technology significantly enhances device usability for users with disabilities, particularly those with motor or visual impairments, by enabling hands-free and sight-free operation. For example, a user with limited hand dexterity can efficiently perform tasks on a smartphone – such as sending texts, making calls, or browsing the internet – just by using voice commands. This hands-free approach allows users who face challenges in physically navigating a touchscreen or keyboard to interact with their devices effectively. The technology's capacity to interpret and execute verbal instructions offers these users greater independence and easier access to digital technology's wide range of functionalities.

Alfie avatar
Written by: Alfie
Cambridge University - BA Maths

A Cambridge alumnus, Alfie is a qualified teacher, and specialises creating educational materials for Computer Science for high school students.

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