Any storage unit of a computer system is ranked according to the following criteria.
This is the time required to locate and retrieve storage data from the storage unit in response to a program instruction. A fast access time is preferred.
It is the amount of data that can be stored in the storage unit. A large capacity is desired.
Types of Storage Unit:
Storage units are basically of two types - Primary and Secondary. As compared to secondary storage units, primary storage units have faster access time, smaller storage capacity, and higher cost per bit of storage.