What is contained in Read Only Memory and cannot be modified by the operator?

Read Only Memory (ROM) is a type of non-volatile memory that is used to store crucial data that is not intended to be modified during regular operation. Among the options presented, the BIOS, which stands for Basic Input/Output System, is a specific example of firmware stored in ROM.

The BIOS is responsible for initializing and testing the system hardware during the booting process and providing an interface between the operating system and the hardware. Since it is stored in ROM, the information contained within is designed to be permanent; users or operators typically cannot modify it without specialized tools or processes, such as firmware updates performed by a manufacturer.

In contrast, operating systems and application software are stored on other types of memory (like hard drives or SSDs), allowing for regular updates and modifications. While firmware may sometimes undergo updates, these updates are typically managed by the manufacturer and not by the average user. Thus, the best answer is the BIOS, which encapsulates the characteristics of being stored in ROM and not modifiable in the typical operational context.