• In general, there are two forms of storage:
• Primary Storage (memory): This sort of storage is mostly used to temporarily store data. The CPU never uses the secondary memory directly, instead relying on the primary memory.
• Secondary storage: This sort of storage is usually used to store large amounts of data or for lengthy periods of time. External devices, such as hard drives, are used to store this form of memory.
• Any data on a disc or input device that cannot be accessed directly by the CPU should always be kept in main memory. The data from the disc memory is accessed by the control unit and stored in the main memory.
• The data remains in primary memory until the application that requires it is run or stopped.

Read More: Explain the difference between rdram and sdram.