Input/output (I/O), in computing, is a communication process (information
processing system) between a computer and the outside world, possibly a
human or another information processing system.
Its most basic level, an
information system, such as a software application, is installed on a computer
and its users in the outside world operate the computer to get solutions to
problems.
Input refers to the signals or instructions sent to the
computer. Output refers
to the signals sent out from the computer.
This term is also known as I/O operations, which
references the input and output actions.
There are input and output
operations performed in a computer context everywhere. Simple common I/O
devices include a keyboard or 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.
INPUT / OUTPUT DEVICE
An input/output (I/O) device is a hardware
device that has the ability to accept inputted, outputted or other processed
data. It also can acquire respective media data as input sent to a computer or
send computer data to storage media as storage output. An I/O device is
also known as an IO device.
INPUT
DEVICE
An input device is a hardware
or peripheral device used to send data to a computer. An input device allows
users to communicate and feed instructions and data to computers for
processing, display, storage and/or transmission.
Examples of input devices include:
- Keyboards
- Mouse
- Joystick
- Scanner
- Digital Camera
OUTPUT DEVICE
An output device is any device
used to send processed data from a computer to another device or
user. Most computer data output that is meant for humans is in the form of
audio or video. Thus, most output devices used by humans are in these
categories.
Examples of output device
include :
- Projectors
- Speakers
- Printers
INPUT
/ OUTPUT INTERFACE
Input/output interface provides a method for
transferring information between internal storage and external I/O devices.
Peripherals connected to a computer need special communication links for
interfacing them with the central processing unit. The purpose of the
communication link is to resolve the differences that exist between the central
computer and each peripheral.
The major differences
are :
Peripherals are electromechanical and
electromagnetic devices and their manner of operation is different from the
operation of the CPU and memory, which are electronic devices. Therefore, a
conversion of signal values may be required.
The data transfer rate of peripherals is usually
slower than the transfer rate of the CPU, and consequently, a synchronization mechanism
may be needed.
Data codes and formats in peripherals differ
from the word format in the CPU and memory.
The operating modes of peripherals are different
from each other and each must be controlled so as not to disturb the operation
of other peripherals connected to the CPU.
To resolve these differences, computer systems
include special hardware components between the CPU and peripherals to
supervise and synchronize all input and output transfers. These components
are called interface units because they interface between the processor bus and
the peripheral device.
Need for I/O interface
Peripherals are electromechanical devices. But
CPU and Memory are electronic devices. Therefore conversion of signal values
may be required.
Data codes and formats in peripherals differ
from the word format in CPU and memory.
Data transfer rate of peripherals are slower
than CPU, so synchronization may be needed.
The operating modes of peripherals are
different. So they must be controlled so as not to disturb the operation of
other peripherals that are connected to CPU.
HIGHER-LEVEL IMPLEMENTATION
Higher-level operating system and
programming facilities employ separate, more abstract I/O concepts and primitives. For
example, most operating systems provide application programs with the concept
of files. The C and C++ programming languages, and operating
systems in the Unix family, traditionally abstract files
and devices as streams, which can be read
or written, or sometimes both. The C standard library provides functions for manipulating streams for input and output.
In the context of the ALGOL 68 programming language, the input and output facilities are collectively referred to as transput.
The ALGOL68 transput library recognizes the
following standard files/devices:
stand in, stand out, stand errors and stand back.
An
alternative to special primitive functions is the I/O monad, which permits
programs to just describe I/O, and the actions are carried out outside the
program. This is notable because the I/O functions
would introduce side-effects to any programming language, but this
allows purely functional programming
to be practical.
CHANNEL I/O
Alternatively
referred to as the input channel, the I/O channel is a line of communication between the
input/output bus or memory to the CPU or
computer peripherals.
PORT-MAPPED I/O
Port-mapped I/O also
requires the use of special I/O instructions. Typically one or more ports are
assigned to the device, each with a special purpose. The port numbers are in a
separate address space from that used by normal instructions.
Post by : Prema Santhini a/p Balasathiah (B031410001)
source 1
: www.techopedia.com
source 2 : http://en.wikipedia.org/wiki/Input/output
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