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Software Engineering For Students: A Programming Approach Part 9. This fully revised version of Doug Bell's Software Engineering: A Programming Approach continues to use the successful formula of the previous editions. The author's approach is to present the main principles, techniques and tools used in software engineering, one by one, chapter by chapter. This book is a unique introduction to software engineering for all students of computer science and its related disciplines. It is also ideal for practitioners wishing to remain current with new developments in the area | 58 Chapter 5 User interface design Each of these qualities can be specified in greater detail as follows Learnability involves predictability - is the effect of any of the user actions predictable A user should never be surprised by the behavior of a system. synthesizability - can the user see the effect of their actions A counter-example of this characteristic is some Unix commands which give the user no information or even a confirmation of what they have accomplished. familiarity - are the facilities familiar to the user from their previous experience The interface should use terms and concepts which are drawn from the anticipated class of user. This attribute will clearly be more easily achieved with an direct manipulation interface. generalizability - can the user safely assume that the same operation in different circumstances gives the same outcome For example does clicking the mouse button on a folder icon have the same effect as clicking on a file icon consistency - are comparable operations activated in the same way For example in a word processor is the selection of a single character a word a line or a paragraph achieved in a consistent manner Flexibility involves user initiative - can the user initiate any valid task whenever they desire This is an issue of who is in control the user or the machine. multi-threading - can several tasks be carried out concurrently For example carrying out text editing while printing is in progress task migratability - can particular tasks be undertaken either by the user or the system or some combination of the two For example some e-mail systems provide for automatic response to e-mail while the user is on vacation. substitutivity - can a facility be used in different ways For example selecting font size either from a menu or by typing font size explicitly. customizability - can the user change the user interface For example hiding an unwanted tool bar adding macros or scripts. Robustness involves observability - does .
