A modem or a router typically converts a computer's data into a format suitable for transmission on a network. The modem modulates digital data from the computer into an analog signal for transmission over telephone lines or cable systems and demodulates incoming signals back. Routers, while primarily responsible for directing data between networks, can also perform similar conversions. Together, these devices facilitate the communication of data across diverse networking architectures, ensuring that the information reaches its intended destination effectively, whether in local or wide area networks.