Input/output In computing, input/output or I/O (or informally, io or IO) is the communication between an information processing system (such as a computer) and the outside world, possibly a human or another information processing system. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it. The term can also be used as part of an action; to "perform I/O" is to perform an input or output operation. I/O devices are used by a person (or other system) to communicate with a computer. For instance, a keyboard or a mouse may be an input device for a computer, while monitors and printers are considered output devices for a computer. Devices for communication between computers, such as modems and network cards, typically serve for both input and output. Note that the designation of a device as either input or output depends on the perspective. Mouse and keyboards take as input physical movement that the human user outputs and convert it into signals that a computer can understand. The output from these devices is input for the computer. Similarly, printers and monitors take as input signals that a computer outputs. They then convert these signals into representations that human users can see or read. For a human user the process of reading or seeing these representations is receiving input. These interactions between computers and humans is studied in a field called human–computer interaction. In computer architecture, the combination of the CPU and main memory (i.e. memory that the CPU can read and write to directly, with individual instructions) is considered the brain of a computer, and from that point of view any transfer of information from or to that combination, for example to or from a disk drive, is considered I/O. The CPU and its supporting circuitry may provide memory-mapped I/O that is used in low-level computer programming, such as the implementation of device drivers, or may provide access to I/O channels. An I/O algorithm is one designed to exploit locality and perform efficiently when data reside on secondary storage, such as a disk drive. Input Devices: Keyboards A 'keyboard' is a human interface device which is represented as a layout of buttons. Each button, or key, can be used to either input a linguistic character to a computer, or to call upon a particular function of the computer. Traditional keyboards use spring- based buttons, though newer variations employ virtual keys, or even projected keyboards. Pointing devices Keyboard devices are the most commonly used input devices today. A pointing device is any human interface device that allows a user to input spatial data to a computer. In the case of mice and touchpads, this is usually achieved by detecting movement across a physical surface. Analog devices, such as 3D mice, joysticks, or pointing sticks, function by reporting their angle of deflection. Movements of the pointing device are echoed on the screen by movements of the pointer, creating a simple, intuitive way to navigate a computer's GUI. High-degree of freedom input devices Some devices allow many continuous degrees of freedom as input. These can be used as pointing devices, but are generally used in ways that don't involve pointing to a location in space, such as the control of a camera angle while in 3D applications. These kinds of devices are typically used in CAVEs, where input that registers 6DOF is required. Composite devices Input devices, such as buttons and joysticks, can be combined on a single physical device that could be thought of as a composite device. Many gaming devices have controllers like this. Technically mice are composite devices, as they both track movement and provide buttons for clicking, but composite devices are generally considered to have more than two different forms of input. • Game controller • Gamepad (or joypad) • Paddle (game controller) • Jog dial/shuttle (or knob) • Wii Remote Imaging and input devices Video input devices are used to digitize images or video from the outside world into the computer. The information can be stored in a multitude of formats depending on the user's requirement. • Digital camera • Digital camcorder • Portable media player • Webcam • Microsoft Kinect Sensor • Image scanner • Fingerprint scanner • Barcode reader • 3D scanner • Laser rangefinder • Eye gaze tracker • Medical Imaging • Computed tomography • Magnetic resonance imaging • Positron emission tomography • Medical ultrasonography Audio input devices In the fashion of video devices, audio devices are used to either capture or create sound. In some cases, an audio output device can be used as an input device, in order to capture produced sound. • Microphones • MIDI keyboard or other digital musical instrument Storage input devices In this device data can be stored. Basic computer components • Keyboard • Image scanner • Microphone Input • Pointing device devices o Graphics tablet o Joystick o Light pen o Mouse o Pointing stick o Touchpad o Touchscreen o Trackball • Webcam o Softcam • Refreshable braille display • Monitor • Refreshable braille display Output • Printer devices • Speakers • Plotter • Optical disc drive o CD-RW o DVD+RW Removable • Disk pack data • Floppy disk storage • Memory card • USB flash drive • Central processing unit (CPU) • HDD / SSD / SSHD • Motherboard • Network interface controller Computer • Power supply case • Random-access memory (RAM) • Sound card • Video card • Ethernet • FireWire (IEEE 1394) • Parallel port Data ports • Serial port • USB • audio jack Types of output Some types of output are text, graphics, tactile,[4] audio, and video. Text consists of characters (letters, numbers, punctuation marks, or any other symbol requiring one byte of computer storage space) that are used to create words, sentences, and paragraphs. Graphics are digital representations of nontext information such as drawings, charts, photographs, and animation (a series of still images in rapid sequence that gives the illusion of motion). Tactile output such as raised line drawings may be useful for some individuals who are blind. Audio is music, speech, or any other sound. Video consists of images played back at speeds to provide the appearance of full motion.[3] Display devices A display device is an output device that visually conveys text, graphics, and video information. Information shown on a display device is called soft copy because the information exists electronically and is displayed for a temporary period of time. Display devices include CRT monitors, LCD monitors and displays, gas plasma monitors, and televisions Audio An audio signal is a representation of sound, typically as an electrical voltage. Audio signals have frequencies in the audio frequency range of roughly 20 to 20,000 Hz (the limits of human hearing). Audio signals may be synthesized directly, or may originate at a transducer such as a microphone, musical instrument pickup, phonograph cartridge, or tape head. Loudspeakers or headphones convert an electrical audio signal into sound. Digital representations of audio signals exist in a variety of formats.[1] Printer (computing) In computing, a printer is a peripheral which makes a representation of an electronic document on physical media. Individual printers are designed to support local and network users at the same time. Some printers can print documents stored on memory cards or from digital cameras and scanners. Consumer and some commercial printers are designed for low-volume, short- turnaround print jobs; requiring virtually no setup time to achieve a hard copy of a given document. However, printers are generally slow devices (30 pages per minute is considered fast, and many inexpensive consumer printers are far slower than that), and the cost per page is actually relatively high. However, this is offset by the on-demand convenience and project management costs being more controllable compared to an out- sourced solution. The printing press remains the machine of choice for high-volume, professional publishing. However, as printers have improved in quality and performance, many jobs which used to be done on printing presses are now done by print on demand or by users on local printers; see desktop publishing. Local printers are also increasingly taking over the process of photofinishing as digital photo printers become commonplace. The world's first computer printer was a 19th-century mechanically driven apparatus invented by Charles Babbage for his difference engine.[1] A virtual printer is a piece of computer software whose user interface and API resembles that of a printer driver, but which is not connected with a physical computer printer. Speech-generating device Speech-generating devices (SGDs), also known as voice output communication aids, are electronic augmentative and alternative communication (AAC) systems used to supplement or replace speech or writing for individuals with severe speech impairments, enabling them to verbally communicate their needs.[1] SGDs are important for people who have limited means of interacting verbally, as they allow individuals to become active participants in communication interactions.[2] Stephen Hawking, physicist and SGD user Projector A projector or image projector is an optical device that projects an image (or moving images) onto a surface, commonly a projection screen. Most projectors create an image by shining a light through a small transparent lens, but some newer types of projectors can project the image directly, by using lasers. A virtual retinal display, or retinal projector, is a projector that projects an image directly on the retina instead of using an external projection screen. Graphics Graphical output displayed on a screen. A digital image is a numeric representation of an image stored on a computer. They don't have any physical size until they are displayed on a screen or printed on paper. Until that point, they are just a collection of numbers on the computer's hard drive that describe the individual elements of a picture and how they are arranged.[5] Some computers come with built-in graphics capability.