There are devices that
perform the activities of an input devices in addtition to those of an output
device. Such devices are called input/output devices or I/O devices.Modems and
network interface cards are examples of input/output devices.
Modem
The term modem stands for
modulator-demodulator. Data can be transmitted over different media, such as
telephone cables and terrestrial transmission. Telephone cables cab carry
waveform called analog signals, analog signals are prone to disturbances from
noise and magetic pilses. A relativerly new form of transmission called digital
uses binary format (an encoding/decoding system based on 0s and 1s) to send and
receive data. This is the format used by computers to send and receive.
However, digital signals to cannot be sent through telephone lines. Hence,
there is a need to convert the digital signals to analog signals before they
are transmitted through telephone cables. Similary, the transmitted data has to
be converted to digital signals at the receiving end. A modem is an electronic
device used to perform the function of converting the digital signals to analog
signals and vice versa.
When you send a massage
from your computer to another computer,
the modem acts as an output device. However,when your computer receives a
message, the modem acts as an input device. A modem can be external or internal to the system
unit. Modems that are connected to the system unit through cables are called
external modems.
Modems are also available
as part of system unit. Modems that are built-in to the system unit are called
internal modems.
Network interface card
A network interface card
(NIC) is a card that is installed in a computer so that it can be connected to a
network. Network interface cards provide a dedicated, full-time connection to
other computers, for example in a classroom.most network interface cards are
designed for a particular type network,although some can serve multiple
networks.in classrooms,thmost typical network is Ethernet. Ethernet is a
network standard of computer communication using either coaxial or twisted pair
cable. Other standards include Tokenring and Framerelay, but these are less common in classroom environments.
