What is a modem ?

When we want to share data between computers, we may use telephone lines, cables or even air as a means of communication. In a computer, information is stored in the form of binary digits, such as zeroes and ones. However, information transferred over the telephone or cable lines is transferred in the form of analog signals. Analog signals are similar to the waves because they vary continuously along with their length.

When two computers communicate with each other over a telephone line, the binary information from the sending end needs to be converted into analog signals that can be sent over a telephone line. Again, at the receiving end, these analog signals need to be converted back to the binary information so that a computer can use the information. The process of converting the binary information into analog signals is called modulation. The    process of converting the analog signal back to the binary information is called demofulation. Modem is a communication device that enables a computer to transfer data over the telephone or cable lines. The word modem is a short form for Modulator / Demodulator.