The term usability describes how useable software is in relation to its intended purpose. A key feature of usability is the way that the human computer interface is designed. An intuitive interface makes using software a lot easier than a ‘clunky’ interface that requires some guess work on the part of the user. Standards in usability vary but a growing trend encourages designers to consider:
- learnability
- memorability
- efficiency
- error handling / reporting
- customisability
Learnability
The term learnability considers how easy an interface is to learn.
If an interface is intuitive with a clear and consistent layout, it is more likely to be usable.
Interfaces that are hard to learn may prevent users from feeling that they can use the software.
Memorability
Memorability describes the concept of how easy an interface is to return to, having not used the software for a period of time.
Software should be designed in such a way that a user can easily return to a level of operation without having to invest time in re-learning the way the interface reacts to user commands.
Efficiency
Different from the efficiency of code mentioned earlier. This is the efficiency of the user experience.
A user interface is efficient if it allows a user to perform a task in the smallest number of steps possible.
Unnecessary navigation to multiple menus is not as efficient as one screen that incorporates the features of each menu.
The use of shortcut keys improves efficiency for experienced users.
Error reporting/handling
Error reporting/handling is the process of designing an interface with easy access to help and/or tutorials if necessary.
Errors that are caused by the user should always result in clear advice on how to proceed.
Customisability
Users vary in experience and skill.
They may have disabilities which make it hard to use a particular size of font or colour scheme.
Being able to customise the user interface of a software package is important for users.
Usability testing
Usability testing is the process of testing software to measure how usable it is. A target group of users is often asked to perform a series of tasks under controlled conditions.
A list of tasks will be given to the test group and measurements such as the amount of time taken to navigate to a certain page will be recorded. Test users are also given a survey or questionnaire to provide feedback to the design team.
To identify a design’s most important usability problems, testing five users is typically enough, often in a one-to-one setting. It is a more efficient use of resources to run many small tests and revise the design between each one so that usability flaws can be fixed as they are identified.
