Human Factors: User Interfaces

Every computer system has an interface that consists of software and hardware, which are needed for users interacting with the system. User interfaces allow people to input commands to the computer, read the computer's output, structure information, and complete certain tasks that may be related to business, education, government, medical, military, industrial, scientific, or home environments. Different types of interfaces allow users to perform a multitude of tasks on a computer, such as creating documents, searching the Internet, or sending and receiving e-mail messages. A user interface may enable a user to enter, locate, manipulate, analyze, monitor, or retrieve information.

Effective user interfaces are extremely important. Many users find computer interfaces difficult to use, and a user's ability to perform tasks on a computer is directly related to the effectiveness of the computer interface. Human-computer interactions should be structured and presented to ease learning, minimize errors, and facilitate use. A poorly designed interface display may lead to user mistakes, non-use of the computer system, and low user satisfaction. In general, interface design needs to answer questions about when, what, and how a user completes a task. User interface designers consider issues such as human memory, color perception, and task complexity to define the display requirements for a computer interface.

Computer games, such as Nintendo and Red Alert, are very popular with people of all ages. Popular computer games include sophisticated interfaces using multimedia effects such as color and sound. Many schools use software programs in the classroom to teach skills and make lessons more interesting for students. The importance of a well-designed user interface is more important than ever as the number of people using computer systems has dramatically increased over the last decade, fueled by the dramatic increase of the Internet on home computers.

Types of Displays

Humans interact with different computer interface displays, such as command line interfaces, menus, natural language, form-fill and spreadsheets, WIMP (windows, icons, menus, and pointers) interfaces, and three-dimensional interfaces. Displays vary in format, type, size, color, and content. Users find color displays attractive, which makes computer software easier to use.

Command line interfaces allow users to give instructions to the computer using commands and keywords. Most online search engines use command line interfaces. Menu-driven interfaces provide the user with a set of options from which to choose. For example, an automated teller machine (ATM) displays a list of options that allow users to deposit and withdraw money and check account balances. Natural language interfaces allow users to communicate with the computer through spoken or written sentences. For example, the Internet search engine "Ask Jeeves" allows users to ask questions when searching for information.

Fill-in forms or spreadsheets present users with a form to complete with numbers or words. For example, to book an airline ticket via the Travelocity web site, a user must complete a form by providing destination and travel details. WIMP interfaces combine various display types and allow users to complete multiple tasks at the same time, click on icons (or pictures), and use their mouse as a pointer. For example, Microsoft Windows allows users to use many software programs at the same time.

Three-dimensional (3D) interfaces are used in virtual reality (VR). For example, computer games often use 3D interfaces and helmet-mounted displays. As the power of personal computer systems increases, the use of 3D interfaces becomes more practical. New types of heads-up displays can project information or images on the windscreen of a car or airplane.

Agents, Direct Manipulation

Computer interfaces may include software agents that perform tasks for users. Agents may perform tasks directly specified by a user, or watch and learn from a user's actions and perform tasks without the user present. For example, an e-mail agent may filter a user's e-mail. Direct manipulation means that specific tasks are represented as pictures to make the task easier for the interface user. For example, to print a document in the word processing package Word, the user can click on a printer graphic to initiate printing.

Software

Software is the sequence of instructions in one or more programming languages or software tools that enable a computer application to automate a task. Computing languages, such as C++ or Java, are used by software engineers to create different types of interfaces with different features, depending on the task for which the interface was designed. Each software program provides users with an interface that allows them to complete a particular task or set of tasks. For example, a word processing interface that allows users to create and modify documents has different features than a web search engine interface. Better software design and software tutorials can make computer interfaces easier to use.

Hardware

Hardware refers to the type of computer used to interact with a software program such as a micro or personal computer. Computer hardware includes the keyboard, mouse, joysticks, and other devices that allow the user to interact with the computer system. New technologies such as speech input, touch screens, and 3D displays increase interface usability. Computers are also getting smaller and more powerful. Portable wireless computers allow users to access the Internet from any location at anytime.

The hardware used in any given system has a significant impact on the user interface that can be designed. For example, the limited screen resolution and processing power available on a wireless telephone limits its ability to perform the intensive 3D graphics that are available on a typical home computer. Improved computer hardware and software can allow users to complete tasks more quickly and effectively, reduce user errors, and minimize the training time and skill needed to use a computer. Specially designed user interfaces are helping younger, blind, elderly, and disabled people use computers. Better interface designs can continue to reduce the potential health risks of prolonged computer use. The interfaces of the future will take users into a 3-dimensional world of virtual reality sight, sound, smell, and touch.

Amanda Spink

Bibliography

Dix, Alan, Janet Findlay, Gregory Abowd, and Russell Beale. Human-Computer Interaction, 2nd ed. London: Prentice Hall, 1997.

Neilsen, Jakob. Designing Web Usability. Indianapolis: New Riders Publishing, 2000.

Shneiderman, Ben. Designing the User Interface: Strategies for Effective Human-Computer Interaction. Reading, MA: Addison Wesley Longman, 1998.