Final answer:
The parts of the OS that remain on a storage medium until they are needed are classified as non-volatile, meaning they retain data without power.
Step-by-step explanation:
The question is asking about a characteristic of certain parts of an operating system (OS) in terms of how they are stored. The parts of the OS that are not immediately active and remain on a storage medium until needed are non-volatile. This means that the data is not lost when the power is turned off. Unlike volatile memory, which requires power to maintain the stored information, non-volatile memory preserves the data even when the device is powered down.