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User Interfaces

User Interfaces

How do we make computers communicate with humans? The first computers, developed in the 1940s, were no more than huge boxes filled with complex electronics. The computer operators used binary code and primitive peripheral devices, such as punched card readers, to communicate with them. The next generation of computers used the typewriter as an input/output device. Since the end of 1960s, monitors and keyboards have become the standard way of communication between computers and humans. Other input devices, such as touch screen, mouse, joystick, scanner, and voice recognition modules, also became available to users. All these devices have made possible the development of interactive computer systems, which permit users to communicate with computers by entering data and control directions during program execution. A part of an interactive computer system that communicates with the user is known as a user interface.

How Computers and Humans Work Together

Interaction between humans and computers is a two-way communication. To interact effectively, users need appropriate tools that are designed specifically for human-to-computer and computer-to-human links. As in communication with each other, people have a natural desire to be able to use a combination of vision, movements, and speech to communicate with computers. Hence, visual, audio, and physical motion components of user interface are interconnected.

Two different visual interface methods, graphical- and character-based, utilize different kinds of actions. The character-based interface typically requires typing on a keyboard. A graphical interface incorporates the use of a mouse or joystick, which translates physical motion into motion of objects on a computer screen. In addition, visual information may be sent from scanners, digital cameras, and faxes, which are able to translate images into computer code.

Speech also may be used, through voice input devices, to deliver system commands and data directly into a system. It is a complex multi-stage process that involves digital sampling of the acoustic signal, recognition of the elements of speech, and even machine knowledge of the language.

All of these methods and devices can be categorized as human-to-computer communication elements. Prompts, messages, and light and sound signals are examples of computer-to-human interaction. A prompt is a signal on a screen indicating that the computer is waiting for a command or data. In response to users' usually brief commands, computers may provide them with reports, graphics, music, links to Internet web sites, and other digitized information or entertainment resources.

Visual Components

The way information is presented on the screen determines what type of user interface is being used. It could be text for DOS or UNIX commands or a graphical user interface (GUI) for a Window-based environment or web-style browser.

For example, Disk Operating System (DOS) is command-driven and requires a user to know more than fifty commands that the system will accept. All commands are entered at the computer prompt. Although it is a reliable operating system, it is not user-friendly since it is not based on the more familiar concepts of graphics and visual cues, which have subsequently been incorporated into the GUI design of window-based user interfaces.

The names and functions of basic GUI elements, such as files, menus, folders, and wastebasket, were selected to correspond to their familiar counterparts in a physical office environment. GUI requires a mouse to move the pointer or cursor, without a keyboard, and uses a point and click sequence. For instance, to select a menu item, an operator uses a mouse or similar device to move the cursor on the screen and highlights the menu item. Then a click or two on a mouse button indicates and executes the selection. Another technique involves choosing an option by entering a letter or number or simple combination of two or three characters that activate the desired option.

Certain software packages use pictures or icons to speed up the selection process. The user can access the function related to each icon by selecting it with the mouse. In this way the user can create, send, file, or discard documents by simply pointing at the appropriate icon. Data entry of specific information may be executed by filling in the appropriate blank fields on a screen form.

Development of the window-based interface was obviously a step forward compared to DOS but its presentation capabilities are limited to the traditional GUI elements that correspond to the paper world of print and graphic design. The emergence of the Internet and World Wide Web brought multimediaa combination of text, images, animation, audio, and videointo a format called a web page. Navigation through various electronic environments and possible connections became a very important concept for web users. While in a Windows software environment, all possible links are pre-defined and limited within each application, web users have full control of navigation, and users can access many types of links for almost unlimited "travel" through virtual environments, interactive files, and interconnected sources of content.

Using Multimedia

As computers become more knowledge- and media-oriented, their input and output devices become more sophisticated. In addition to graphics, other forms of data presentation, such as voice, music, and video are also available to users.

In voice input devices, speech produced by an operator is used to enter data or system commands directly into a computer system. Computers may also have speech-generation devices to deliver oral messages in response to signals from a data processing or control system. Messages are created by assembling elements of real speech or by the synthesis of sound waves of certain frequency.

A computer-vision system allows the user to create, save, and reproduce video images. The system consists of a camera connected to a personal computer to create images and software that permits the user to experiment with image processing.

Virtual reality (VR) environments project the user into a simulated three-dimensional space generated by a computer. The illusion of being surrounded by a world of computer-generated images, or a virtual environment, is created by linking the motion of a user's head with changes in the images presented in the visual display. The use of a data glove and head-mounted stereoscopic display allow users to point to and manipulate illusory objects that appear within their view.

Interfaces for Specialized Computers

Making computers widely accessible to people with varying physical abilities requires customization of interactive styles for different user communities. For example, users with fine motor disabilities may utilize alternative input devices, such as programmable keyboards, which permit them to operate computers with limited use of hands. They can enter letters, numbers, words, or even phrases by using functional keys. Another way to enter data into the computer is to operate an electronic pointing device, which allows a user to move the cursor on the screen using ultrasound or an infrared beam. Utilizing speech recognition software is another way to make computers accessible to users unable to use manually operated input devices.

A variety of interface systems are widely used by health care practitioners and scientists. Medical doctors are able to study body organs by manipulating three-dimensional digital images. Chemists may observe the progression of simulated chemical reaction in slow motion. Scientists can rotate and re-size objects in hypothetical models, and change their angle and point of view. Environmental scientists and geographers may compile, retrieve, and visualize various geographic data, including maps in a three-dimensional format.

Telecommunication devices enable users to transmit text, graphics, video, and voice over a distance using computers. PC users now send electronic- or voice-mail all over the world and can exchange ideas and news in chat rooms and via instant messaging software programs.

Computer interface designers are challenged by the goal of creating an interface that resembles human-to-human interaction as closely as possible. Design considerations should include not only technical aspects but ergonomic factors as well. The ideal interface would allow one to concentrate on his or her work without even being aware of the presence of the interface itself.

see also Ergonomics; Interactive Systems; Window Interfaces.

Marina Krol and Igor Tarnopolsky


Dertouzos, Michael L. The Unfinished Revolution: Human-Centered Computers and What

They Can Do for Us. New York: HarperCollins, 2001.

Shneiderman, Ben. Designing the User Interface: Strategies for Effective Human-Computer Interaction. Reading, MA: Addison Wesley Longman, Inc., 1997.

Weinschenk Susan, Sarah C. Yeo, Pamela Jamar, and Theresa Hudson. GUI Design Essentials for Windows 95, Windows 3.1, World Wide Web. New York: John Wiley & Sons, 1997.

Weiss, Elaine. Making Computers People-Literate. San Francisco: Jossey-Bass Inc., 1994.

Internet Resources

"Human-Computer Interaction." IBM Research web site. <>

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User Interface


For a long time, the ease with which humans and computers interacted was not a primary area of focus. The earliest computers relied on interfaces that by modern standards were very primitive and cumbersome. As computing became a part of life for more than just a handful of scientists, academics, and businesspeople, it became necessary to devise user interfaces that were not terribly difficult to understand and use. The field of human-computer interaction evolved, leading to systems that were much easier for the average person to operate.

In general, the term user interface can apply to the many different means humans have for interacting with computer systems, applications, and networks. These include everything from physical tools like monitors, mice, light pens, keyboards, and microphones (for voice recognition commands and audio input) to elements that appear on screen, such as basic text characters used for writing programs and issuing commands, help modules in software applications, search tools, and the graphical user interfaces (GUI) characteristic of the Macintosh and Windows operating systems. The term user interface even applies to the ways in which Web sites, wireless devices, and e-commerce applications are set up for interaction with customers.

The earliest user interfaces were limited to only a few buttons on a computer device or punch cards that contained instructions. Text-based, on-screen interfaces, such as a list of menu choices, eventually became available. They evolved into the GUIscontaining toolbars, pointers, pop-up windows, virtual desktops, and iconsthat were very pervasive across different computing platforms, systems, and devices in the early 2000s. Because GUIs rely heavily on visual elements, these interfaces became increasingly sophisticated and subjective, and were received and interpreted by a diverse population of computer users in different ways.

When users find a particular interface appealing and understandable, it becomes possible to take full advantage of all the capabilities the underlying system or application has to offer. Otherwise, a poor interface can limit the power and potential uses of the system or application. Although it was arguably easier to operate computers and operating systems in the early 2000s than it was at the beginning of the computer age, poorly designed user interfaces were an issue for many software programs. Making matters worse was the fact that bad interface precedents set by leading software companies were sometimes followed by other players throughout the industry. Isys Information Architects Inc. was one company specializing in information systems design during the early 2000s. According to Isys, among the leading roadblocks to effective interfaces were hard-to-understand terminology, improperly used metaphors and visual element design, unclear or incorrect error messages, and the misuse of color.

The degree to which a user finds an interface easy to understand and use not only affects the extent to which he or she can take advantage of what the system has to offer, it also may impact how often the user operates a system. For companies engaging in e-commerce, this can have serious implications. Even if a company has a product or service that consumers want, and at a price that is competitive, a frustrating or confusing online experience can kill a potentially lucrative sale. Therefore, it is necessary for e-commerce Web sites and their underlying systems to be well designed.

In the early 2000s, personal digital assistants (PDAs) like the Palm Pilot, and various kinds of handheld computers and wireless Internet-enabled phones were exploding in popularity. These devices held great promise for e-commerce. The development of user interfaces for these devices was an emerging area that presented a variety of challenges. Among them was the issue of getting modern wireless devices to not only communicate with older legacy systems (common at many companies), but to then present the data in a format that was easy to understand and navigate.


"Interface Hall of Fame/Interface Hall of Shame." Isys Information Architects Inc. July 31, 2001. Available from

Zetlin, Minda. "The Web's Master Builders." Computerworld, January 22, 2001

SEE ALSO: Web Site Design

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user interface

user interface (UI) The means of communication between a human user and a computer system, referring in particular to the use of input/output devices with supporting software. Examples include the graphical user interface (GUI) and command-line interface (CLI).

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