Storage Ranking:

Any storage unit of a computer system is ranked according to the following criteria.

Access time:

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.

Storage capacity:

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.

Relevant Articles: Storage Ranking Storages Locations and Addresses Why More Bits Fixed and Variable Word Length Storage Bits, Bytes, and Words Internal Memory Devices External Memory Devices Organizing and Accessing Stored Data Types of Files Processing Stored Data