11.3 Principle for User Interface Design

The goal of designing a good user interface is to make the user interface pleasing to the eye and easy to use, and at the same time minimizing the user effort in accomplishing their task. There are several principles that need to be considered when designing a user interface.

11.3.1 Easy to Use

First and the most important things in designing a good interface is it should be designed clearly labeled with all controls, buttons and icons. If the images are used in the interface, select only images that users can understand easily. For example; house images, can be used to represent the go back command. Figure 11-7 shows an example of images and commands that can be used in any interface design. The interface also need to provide on-screen instructions that are logical, concise and clear. A good interface design is an interface which is easy to navigate or return to any level in the menu structure.

Figure 11-7: Icon and Commands

11.3 Principle for User Interface Design

11.3.2 An Attractive Layout

The important element in any user interface design is the basic layout of the screen, form, or report. When designing interface, we should have and follow a standard formats for computer-based forms and reports similar to those the paper-based one. Most of the screen is divided with at least three main components :

	Header
	Body or data details
	Comments or signatures

The above components apply when designing input and output. When designing layouts to records or display information from a paper-based forms, we should try to make is as similar as possible with computer-based forms and reports.

A good layout with creative and attractive design can attract users in using the system. Use appropriate colors in order to highlight different areas of the screen, but need to avoid gaudy and bright colors. The use of animations and sound might be effective in some situations, but not too many special effects. For example, when designing an e-learning system, it can attract users especially kids when the system contains animations and sounds. Every layout has its own title. Arrange the title of the screen accordingly in a consistent manner together with its messages and instructions.

11.3 Principle for User Interface Design

When a user enters data, please ask the users to reconfirm their input before it goes to the next field. Ensure that all the available commands have same meaning. For example, if NEXT control button indicates that the next screen will appears, the NEXT button should always perform the same command throughout the system.

11.3.3 Minimize Input Errors

One objective of user interface design is to reduce data input errors. As data input are entered into a system, steps must be taken to ensure that the input is valid. It's important to provide data validation checks. As a system analyst, we must anticipate the types of errors users may make and design features into the system's interface to avoid, detect, and correct data input mistakes. Establish a list of predefined values that users can click to select. Predefined values prevent spelling errors, avoid inappropriate data in a field and make the user's job easier - the input screen displays a list of acceptable values and the user simply points and clicks the choice. There are several types of tests conducted for catching the invalid data before saving or transmission. There are several validation tests that can be conducted such as class or composition, combination, expected values, missing data, range, self-checking digits, size and values. Most of these tests are widely used and since it is a straightforward technique. It is a need and easier to correct the data before permanently stored in a system. The other way is, the system can notify users of input errors as data are being entered.

In addition to data validation tests, control must be established to verify that all input records are correctly entered and that they are only processed once. A common method used to enhance the validity of entering data records is to create an audit trail of the entire sequence of data entry, processing and storage. If an error occurred, correction can be made by reviewing the contents of the log.

11.3 Principle for User Interface Design

When entering data, a user should also not be required to specify units of a particular value. Field formatting and the data entry prompt should make easier and clear the type of data being requested. The use of input mask, which is a template or pattern that make it easier for users to enter data. In other words, a caption describing the data to be entered should be in a same format to the requested data field. As with the display of information, all data entered onto a form should automatically justify in a standard form.

Figure 11-8: Status information provided by the System

11.3 Principle for User Interface Design

	Prompting cues
	It is a system feedback used to display prompting cues. When prompting the user for information or action, it is useful to be specific in your request. With a prompt, system designer assumes that the user knows exactly what to enter. For example :

Enter your Matric Number (XXX12345): ________

	Error or warning messages
	This system feedback display messages that is specific and free of error codes. This message should guide the users toward a resolution. For example :

Sorry, No Student Found with the Matric Number