What is the main function of a modem?

The primary function of a modem is to modulate and demodulate signals for data transmission. This process allows digital data from a computer to be converted into analog signals suitable for transmission over telephone lines or other communication channels. Conversely, when receiving data, the modem demodulates the incoming analog signals and converts them back into digital data that the computer can understand. This modulation and demodulation is essential for enabling devices to communicate over various types of networks, such as the internet.

In contrast, enhancing graphical quality pertains to the function of graphics cards or display adapters, which are responsible for rendering images and visuals. Managing user accounts is typically handled by operating systems or specific application software designed for user management, and is unrelated to modem functionality. Providing wireless connectivity is a role fulfilled by equipment such as routers or wireless access points, not modems, although some modern modems do integrate these functionalities. Thus, the correct answer about the modem's role in signal modulation and demodulation accurately captures its essential function in data communication.