Primary Storage, also known as main storage or memory, is the main area in a computer in which data is stored for quick access by the computer's processor. Information must be transferred to primary storage. On today's smaller computers, especially personal computers and workstations, the term random access memory (RAM) - or just memory - is used instead of primary, main storage, core memory, or immediate access storage, internal storage, and the hard disk, diskette, CD, and DVD collectively describe secondary storage or auxiliary storage.
It allows very fast access to data. It is relatively move expensive. A CPU has three element or parts primary storage, arithmetic logic unit (ALU), and control unit. Primary storage is fast and expensive as compared to secondary storage.
The terms main storage and auxiliary storage originated in the days of the mainframe computer to distinguish the more immediately accessible data storage from storage that required input/output operations.