User Interface

I

Introduction

User Interface, in computer science, components humans use to communicate with computers. A computer user directs the function of a computer with instructions called input. Input is entered by various devices, such as a keyboard, and is translated into electronic signals that a computer can process. These signals pass along circuit pathways known as buses and are coordinated and controlled by the central processing unit (CPU) (the computer circuitry that performs arithmetic and logical functions), and software known as the operating system. Once the CPU has performed the commands directed by the user, it may communicate the results by sending electronic signals, called output, back along the bus to one or more output devices, such as a printer or video display monitor.

In addition to a computer's speed the usability of the software and the ergonomic design of the physical components are important considerations. Usability is the ease with which a person learns to use an application, as well as how efficient and effective it is. Ergonomics determines how people function in relation to their environment, and with respect to computers, how to make input and output devices easy, comfortable, and efficient to use. For example, curved ergonomic keyboards prevent wrists from bending at unnatural angles, making the user more comfortable and input faster.

II

Input and Output Devices

A variety of devices are used to enter data. Most personal computers (PCs) include a keyboard because it is easy to use and efficient for everyday tasks such as word processing. A mouse, trackball, and joystick are other input devices that help the user point, select, and move objects on a video display monitor. Handwriting can be entered on a computer's screen using light pens, wands that contain sensors to translate the user's motions into data. Touch screens in which infrared light sensors detect a user's fingers are used in environments where keyboards are unsuitable, such as cash dispensing machines. Sound and speech recognition are popular for some applications, but these input devices are still imperfect and usually understand and respond to only a small vocabulary of commands.

The most familiar output devices are printers and color video display monitors. Audio output is also common, as well as sophisticated connections to synthesizers that produce a wide range of musical sounds (see MIDI).

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III

Command and Graphical Interface

Dialog between the user and the computer is usually accomplished by command-line or graphical user interfaces (GUIs). Command-line interfaces require the user to type brief commands on a keyboard to direct the computer's actions. GUIs use windows to organize files and applications represented by icons (small pictures) and menus that list commands. The user directly manipulates these visual objects on the video display monitor by pointing, highlighting, and dragging or by moving them with a mouse or trackball.

GUIs are easier to learn than command-line interfaces, since commands need to be memorized and tend to vary between different computer systems. Entering commands with a GUI is slower, however, so GUIs usually have optional command-line equivalents as a quick alternative for more experienced users.

IV

Special Systems

Some users require special interfaces. Visually impaired people, for example, use screen readers to translate individual lines of text from the screen into speech, and printers that produce text in the Braille system. Adopting graphical interfaces for the visually impaired is more difficult, although some word processors provide menus, windows, and icons with auditory properties that make sounds when the cursor passes over them, or when the cursor passes into off-screen areas. Some systems, however, have yet to be adequately developed for the visually impaired, such as web browsers, the visual interface system that accesses the global information database known as the World Wide Web.

In 2006 researchers reported the first interface device that directly links a human brain to a computer, allowing a user to perform tasks by brain cell activity alone. The experimental device, called the BrainGate Neural Interface System, allowed a paralyzed man to move a computer cursor, draw shapes, and play video games simply by imagining the movements. He also could manipulate a prosthetic hand and a robotic limb. A sensor implanted in his brain detected electrical activity from his motor cortex that an external processor then converted into computerized signals. The discovery that the brain signals that originally controlled a limb remain available and usable years after a spinal cord injury is a breakthrough. This pioneering neuroprosthetic system is seen as a first step toward computer interfaces with the brain that could bypass spinal cord injuries or disease-damaged nerves to reactivate paralyzed limbs. In addition to allowing greater movement and communication, future devices might be designed to write images into the brain of a blind person or to perform other complex functions.

Virtual reality (VR) provides users with the illusion of being in a three-dimensional (3D) world. There are two types of VR systems: immersive and nonimmersive. Immersive systems involve wearing a head-mounted display or helmet and data gloves that translate the user's hand motions into data the computer can process. This VR interface enables the user to directly experience a simulated environment. The user can turn, pick up, throw, or push computer-generated objects using gestures similar to those they would normally use. In VR, users are aware of the simulated environment and their actions through visual, auditory, and some tactile sensations. Immersive VR is used for applications such as pilot training systems, computer games, and medical training. Nonimmersive VR systems display alternate environments for the user to navigate through but do not require users to wear specialized equipment. Instead, users rely on conventional devices such as video display monitors, keyboards, and a mouse to manipulate the simulated environment.

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