The function of a BIOS (Basic Input/Output System) in a computer is to initialize and test the system hardware during the booting process and to load the operating system. The BIOS performs a POST (Power-On Self-Test) to check the integrity of hardware components such as the CPU and RAM. Once the hardware is confirmed to be operational, the BIOS locates and loads the boot loader, which then transfers control to the operating system. It also provides a low-level interface for hardware control and allows users to configure system settings. Thus, the BIOS serves as a crucial bridge between hardware and software.