User interface design

Software engineer is responsible for user interface design. User interface to be text based or text based.

Characteristics of GUI

1- They are relatively easy to learn and use. Users with no computing experience can learn to use the interface after a brief training session.

2- The user ahs multiple screens (windows) for system interaction. Switching from one task to another is possible without loosing sight of information generated during the first task.

3- Fast, full screen interaction is possible with immediate access to anywhere on the screen.

Characteristics Description

Windows Multiple windows allow different information to be displayed

simultaneously on the user screen.

Icons Icons represents different type of information. On some system,

icons represent files, on other icons represents processes.

Menus Command are selected from menu rather than typed in a language.

Pointing A pointing device such as mouse is used for selecting choice from

menu.

Graphics Graphical elements can be mixed with text on the same display.

User interaction

The design of a user interface to a computer is faced with 2 key issues.

1- How can information from the user be provided to computer system.

2- How can information from the computer system be presented to user.

A coherent user interface integrates user interaction & information presentation. We have classified different forms of interaction into 5 primary styles.

Direct manipulation where user interact with objects on the screen. e.g. to delete a file.

Menu selection where user selects a command from list of possibilities.

User interface design principles

Principle Description

User familiarity The user should use terms and concept which are drawn from the

experience of the people who will make most use of the system.

Consistency The interface should be consistent in that wherever possible,

comparable operation should be activated in the same way.

Minimal surprise Users should never be surprised by the behavior of a system.

Recoverability The interface should include mechanism to allow user to recover from errors.

User guidance The interface should provide meaningful feedback when errors occur and provide context sensitive user help facility.

User diversity The interface should provide appropriate interaction facilities for different type of system user.

User interaction

Interaction style Main advantage Main disadv. Application ex.

Direct manipulation Fast & intuitive May be hard to Video games,

Interaction, easy implement, only CAD system

to learn suitable where there

is visual metaphor for

task & objects

Menu selection Avoid user error, Slow for experienced Most general

Little typing users, can become purpose

Required complex if many menu system

Option

Form fill in Simple data entry, Takes a lot of screen Stock control,

easy to learn space personal loan

processing

Command language Powerful & flexible Hard to learn, poor operating

Error management system, library

Information retrieval system

Natural language Accessible to casual Requires more typing, Time table

Users, easily natural language system,WWW

Extended understanding system information

are unreliable retrieval system

Information presentation

All interactive system has to provide some way of presenting information to users. Finding the best presentation needs knowledge of the background of the users & the way in which they used the system.

In deciding how to present information, the designer must take a number of factors into account.

1- Is user interested in precise information or in the relationship between different data values?

2- How quickly does the information value change? Should the change in a value indicated immediately to the user.

3- Must user take some action in response to change in information?

4- Does the user need to interact with displayed information via direct manipulation interface?

5- Is the information to be displayed textual or numeric? Are relative values of information items important?

Color in interface design

Color can improve user interface by helping users understand and manages complexity. However it is easy to misuse and to create user interface that are visually unattractive and error prone. Some important guidelines are:

1- Limits the number of colors used and be conservative how they are used. Not used more than four or five.

2- Use color change to show a change in system status. If a display changes color, this means a significant event occurs.

3- Used colors coding to support the task which are user are trying to perform.

4- Use color coding in a thoughtful and consistent way.

5- Be careful about color pairing, because of physiology of eye, people cannot focus on red & blue simultaneously.

Color should not used represent the meaning

1- Red color mean danger for driver

2- Red color mean hot for chemist.

User support

User interface provides some help system. Help system are one facet of a general part of a user interface design. There are three criteria for user support:

1- The message produced by the system in response to user actions.

2- The online help system

3- The documentation provided with system

Error message

Factors Description

Context The user guidance system should be aware of what the user is doing and should adjust the output message to the current context.

Experience

Skill level

Style message should be positive rather than negative. There should be active rather than passive. They should never be insulting or never trying to funny.

Culture

Help design system

Helps mean help when I am in trouble. Another help means help I want information.

User documentation

User documentation is not strictly part of user interface design. To cater different classes

of user, there are different types of documentation.

1- Functional description which should be describes, very briefly, the services which system provides. User should be able to read document with introductory manual and decides what system needs.

2- An installation document provides details how to install a system, it should

Describe the disks on which system is supplied, the files on these disks and minimal h/w configuration is required.

3- Introductory manual which presents an informal introduction to the system describing its normal usage. It should describe how to get started and now end users user the common system facilities.

4- A reference model should describe the system facility and their usage, provide a list of errors message and possibly caused & describe how to recover from detected errors.

5- An administrator manual provides same types of system. It describes the message generated when system interacts with other system & how to react to these messages. If system h/w is invalid it explains how to recognize & repair h/w related problems. How to connect peripherals.

Interface peripherals

Interface evaluation is process of assessing the usability of an interface and checking that it meets requirements. It is part of verification & validation process for s/w system.

Attributes Description

Learn ability How long does it take for a new user to became productive with the system.

Speed of operation How well does the system response match the user work practice.

Robustness how tolerant is the system of user error.

Recoverability how good the system at recovering from user errors.

Adaptability How closely is the system tied to a single model of work.