Alternative Methods of Input Devices for the Hand

With a pen-based system, you use a "pen" (also called a stylus) to write on a special pad or directly on the screen. Pen-based computers are handy for writing notes or selecting options from menus, but they are not well suited for inputting long text documents because handwriting-recognition technology has not yet achieved 100 percent reliability.

Touch-screen systems accept input directly through the monitor. Touch-screen systems are useful for selecting options from menus, but they are not useful for inputting text or other types of data in large quantities.

A game controller is a special input device that accepts the user's input for playing a game. The two primary types of game controllers are joysticks and game pads.

Optical Input Devices

Bar code readers, such as those used in grocery stores, can read bar codes, translate them into numbers, and input the numbers into a computer system.

Image scanners convert printed images into digitized formats that can be stored and manipulated in computers. An image scanner equipped with OCR software can translate a page of text into a string of character codes in the computer's memory.

Audiovisual Input Devices

Microphones can accept auditory input. Using speech-recognition software, you can use your microphone as an input device for dictating text, navigating programs, and choosing commands. To use a microphone or other audio devices for input, your computer must have a sound card installed. A sound card takes analog sound signals and digitizes them. A sound card can also convert digital sound signals to analog form.

PC video cameras and digital cameras can digitize full-motion and still images, which can be stored and edited on the PC or transmitted over a LAN or the Internet.

Monitors and Sound Systems Monitors

Computer monitors are roughly divided into two categories: CRT and flat-panel displays.

Monitors can also be categorized by the number of colors they display. Monitors are usually monochrome, grayscale, or color. A CRT monitor works with one or more electron guns that systematically aim a beam of electrons at every pixel on the screen. Most LCD displays are either active matrix or passive matrix. When purchasing a monitor, you should consider its size, resolution, refresh rate, and dot pitch.

The video controller is an interface between the monitor and the CPU. The video controller determines many aspects of a monitor's performance; for example, the video controller lets you select a resolution or set the number of colors to display. The video controller contains its own on-board processor and memory, called video RAM.

Pc Projectors

A PC projector is a portable light projector that connects to a PC. This type of projector is rapidly replacing traditional slide projectors and overhead projectors as a means for displaying presentations. Many PC projectors provide the same resolutions and color levels as high-quality monitors, but they project the image on a large screen. The newest PC projectors use digital light processing to project bright, crisp images. A DLP projector uses a special microchip that contains tiny mirrors to produce images.