What is one of the main functions of a hard drive in a computer system?

One of the main functions of a hard drive in a computer system is to store data permanently. Hard drives are designed to retain large volumes of information, such as operating systems, applications, and user files, even when the computer is powered off. This persistence is crucial for ensuring that data is not lost when the device is not in use. Unlike RAM (random access memory), which is volatile and loses its contents when the power is turned off, hard drives maintain data over time, making them essential components for any computing system that requires long-term data storage.

The other functions mentioned in the other choices pertain to different hardware or components within a system, such as the CPU for calculations, input devices for processing user input, and the GPU or display hardware for controlling video output. These roles highlight the specialized functions of various parts of a computer, each contributing to the overall operation of the system.