Aspects of User Interface Design

There are a large number of publications  that discuss how to design a good user interface, some offering ``standard'' interface design guidelines.

Two conclusions may be obtained from these publications. Firstly, the interface should be consistent with other applications on that platform. Secondly, when a user is required to perform a task, it should be consistent with their computing experience.

For evaluating the effectiveness and quality of user interface designs, Nielsen  has created a list of ten usability guidelines, which summarise most design guidelines.  

• Visibility of system status. The system should always keep users informed about what is going on, through appropriate feedback within reasonable time.

• Match between system and the real world. The system should speak the user's language, with words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order.

• User control and freedom. Users often choose system functions by mistake and will need a clearly marked ``emergency exit'' to leave the unwanted state without having to go through an extended dialogue. Support undo and redo.

• Consistency and standards. Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.

• Recognition rather than recall. Make objects, actions and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.

• Flexibility and efficiency of use. Accelerators, unseen by the novice user, may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.

• Aesthetic and minimalist design. Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.

• Help users recognise, diagnose, and recover from errors. Error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution.

• Error prevention. Even better than good error messages is a careful design which prevents a problem from occurring in the first place.

• Help and documentation. Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user's task, list concrete steps to be carried out, and not be too large.

The use of colour in a user interface is also an important consideration. While the use of colour can provide a lot of useful feedback to the user, the designer must consider the fact that monochromatic displays are still used, as well as the existence of problems such as colour-blindness. 1 in 11 males and 1 in 300 females are colour blind. 1 in 3 million people have complete colour blindness.