Output devices are pieces of computer hardware that allow a computer system to communicate information to a user or another system. This information can be in any form, and includes sound, images, and even tactile experiences. Output devices can usually only be used to send data from the computer; items called input devices allow users and other systems to send data to the computer.
Some of the most common output devices allow computers to present information visually. The visual display unit called a monitor that can be found connected to almost every personal computer is the best example of this. Text, pictures, and other images are displayed on the monitor, allowing users to interact with computer programs and receive data. Video projectors are another type of output device. They function in a way similar to monitors, but display images over a much larger area. Computer printers are another type of output device that can be easily found. Printers allow the computer to produce documents, pictures, and images on paper through the use of inks and other dyes.
Audio output devices are also common. Computer speakers are the primary source of this form of output. They allow the computer to emit sounds that include music, audio tracks to digitized television shows, and even the voices of other users. Headphones also do the same thing, but are placed closer to the ears so that the sounds can not be heard by others.
Computers can even communicate with users through the sense of touch. Refreshable Braille displays, or Braille terminals, allow computers to send information by way of raised dots that are “read” with the fingertips. Force feedback devices, or haptic devices, are sometimes built into joysticks and mice so that users can feel vibrations and pressure. Tactile output devices are less common than many other types, but can still be extremely important to users.
Rarely, output devices can also be input devices. A storage device such as a CD-RW drive is an excellent example of this. The computer uses it as an output device when it is writing information to a CD-ROM or other media that can be read by other computers. However, the computer uses it as an input device when reading information from a CD-ROM or other piece of storage media that has data written on it from another system.