In computer networking, a modem (modulator–demodulator) is used primarily for which purpose?

Introduction / Context:
The term modem is short for modulator–demodulator. Modems have played a crucial role in enabling computers to communicate over telephone lines, cable systems and other communication media. This question asks what modems are mostly used for in practical computing and networking, focusing on their primary function rather than on unrelated computer tasks.

Given Data / Assumptions:
- We consider typical usage of modems in home and office networks.
- Options describe uses related to internet connectivity, memory, file systems and general computer functions.
- We assume a standard definition of a modem as an interface device for communication lines.

Concept / Approach:
A modem converts digital signals from a computer into analog or otherwise suitable signals for transmission over communication lines (modulation) and converts incoming signals back into digital form (demodulation). Its main role is to enable data communication between a local computer or router and a remote network such as the internet. It is not a memory component, does not directly manage the file system, and does not perform all computer functions. Therefore, the correct answer involves connecting to networks, typically the internet.

Step-by-Step Solution:
Step 1: Recall that a modem stands for modulator–demodulator, indicating its signal conversion function. Step 2: Understand that in traditional dial-up networking, modems converted digital computer data to audio tones for telephone lines and back again at the receiving end. Step 3: Modern cable and DSL modems perform similar roles for broadband connections, converting between digital signals on the local network and signals suitable for the service provider's infrastructure. Step 4: Recognise that this conversion allows computers and routers to connect to remote servers on the internet through these communication lines. Step 5: The modem is not used as memory, does not manage file systems and does not automatically perform all computer operations. Step 6: Therefore, the primary use of a modem is to connect computers or local networks to wider networks such as the internet.

Verification / Alternative check:
In a typical home setup, an internet service provider supplies a modem or modem–router combination. The modem connects to the external line (telephone, cable or fibre) and to a router or directly to a computer. The device's documentation describes it as enabling internet connectivity rather than as a memory component or file manager. This practical experience confirms that the correct purpose is network or internet connection.

Why Other Options Are Wrong:
Providing empty memory modules inside a computer: Memory is handled by RAM and storage devices such as hard drives or SSDs, not by modems.
Managing the internal file system on a hard disk: File systems are managed by the operating system and storage controllers, not by the modem.
Performing all possible computer functions automatically: This is too broad and incorrect; a modem is a specialised communication device, not a general-purpose processor.

Common Pitfalls:
Some learners may see the word modem used in a casual way and think it refers to any network device or even the entire router. While many home devices combine modem and router functions into one box, the modem portion specifically handles the conversion between local digital signals and the external communication line. Keeping this distinction in mind helps answer conceptual exam questions about modems correctly.

Final Answer:
A modem is used mostly for connecting computers or local networks to communication lines, such as the internet.