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Input/Output devices


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.

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