2. INPUT AND OUTPUT
DEVICES
I/O devices are the pieces of hardware used by a human (or other system) to
communicate with a computer. For instance, a keyboard or computer mouse is
an input device for a computer, while monitors and printers are output devices.
Devices for communication between computers, such as modems and network cards,
typically perform both input and output operations
3. A computer keyboard is a typewriter-style device which uses an arrangement of
buttons or keys to act as mechanical levers or electronic switches. Replacing
early punched cards and paper technology, interaction via teleprinter-style keyboards
have been the main input method for computers since the 1970s, supplemented by
the computer mouse since the 1980s
4. MOUSE
A computer mouse (plural mice, rarely mouses) is a hand-held pointing device that
detects two-dimensional motion relative to a surface. This motion is typically
translated into the motion of a pointer on a display, which allows a smooth control of
the graphical user interface of a computer.
The first public demonstration of a mouse controlling a computer system was in 1968.
Mice originally used a ball rolling on a surface to detect motion, but modern mice often
have optical sensors that have no moving parts. Originally wired to a computer, many
modern mice are cordless, relying on short-range radio communication with the
connected system.
5. JOYSTICK
A joystick is an input device consisting of a stick that pivots on a base and reports its
angle or direction to the device it is controlling. A joystick, also known as the control
column, is the principal control device in the cockpit of many civilian and military
aircraft, either as a centre stick or side-stick. It often has supplementary switches to
control various aspects of the aircraft's flight.
Joysticks are often used to control video games, and usually have one or more push-
buttons whose state can also be read by the computer. A popular variation of the
joystick used on modern video game consoles is the analog stick. Joysticks are also
used for controlling machines such as cranes, trucks, underwater unmanned vehicles,
wheelchairs, surveillance cameras, and zero turning radius lawn mowers
6. LIGHT PEN
One of the first more widely deployed uses was in the Situation Display consoles of
the AN/FSQ-7 for military airspace surveillance. This is not very surprising, given its
relationship with the Whirlwind projects. See Semi-Automatic Ground Environment for
more details
Because the user was required to hold their arm in front of the screen for long periods
of time (potentially causing "gorilla arm") or to use a desk that tilts the monitor, the
light pen fell out of use as a general-purpose input device
7. SCANNER
An image scanner—often abbreviated to just scanner, is a device that optically
scans images, printed text, handwriting or an object and converts it to a digital image.
Commonly used in offices are variations of the desktop flatbed scanner where the
document is placed on a glass window for scanning. Hand-held scanners, where the
device is moved by hand, have evolved from text scanning "wands" to 3D
scanners used for industrial design, reverse engineering, test and
measurement, orthotics, gaming and other applications. Mechanically driven scanners
that move the document are typically used for large-format documents, where a
flatbed design would be impractical.
8. A computer monitor is an output device that displays information in pictorial form. A
monitor usually comprises the visual display, circuitry, casing, and power supply.
The display device in modern monitors is typically a thin film transistor liquid crystal
display (TFT-LCD) with LED backlighting having replaced cold-cathode fluorescent
lamp (CCFL) backlighting. Older monitors used a cathode ray tube (CRT). Monitors are
connected to the computer via VGA, Digital Visual
Interface (DVI), HDMI, DisplayPort, Thunderbolt, low-voltage differential signaling (LVDS)
or other proprietary connectors and signals.
Originally, computer monitors were used for data processing while television sets were
used for entertainment. From the 1980s onwards, computers (and their monitors) have
been used for both data processing and entertainment, while televisions have
implemented some computer functionality. The common aspect ratio of televisions, and
computer monitors, has changed from 4:3 to 16:10, to 16:9.
