What is the function of CMOS in a computer system?

The function of CMOS in a computer system is primarily to store start-up information for the BIOS (Basic Input/Output System). This includes essential data such as system settings, hardware configurations, and configuration specifics required for the computer's initial boot process.

CMOS (Complementary Metal-Oxide-Semiconductor) technology uses minimal power and is well-suited for storing small amounts of memory that must be retained even when the computer is powered off, which is achieved through a small battery. This is crucial because the BIOS needs to know specific settings each time the system is powered on, such as the boot order of devices and system clock settings.

In contrast, other options list functions not associated with CMOS. For example, storing user files pertains to hard drives or SSDs, the main processing unit relates to the CPU, and internet connectivity is provided by network interface cards or modems. These distinctions highlight why the primary role of CMOS is centered around storing the vital information necessary for the BIOS to execute its start-up duties effectively.