Computers use main memory such as random-access memory (RAM) and cache to hold data that is being processed. However, this type of memory is volatile - it loses its contents when the computer is switched off.
The secondary memory is always a non-volatile memory. Non-volatile memory is memory that retains its values even when power is removed.It is an external memory of the computer. Secondary memory is known as a Backup memory or Additional memory or Auxiliary memory.
Secondary memory is slower than primary memory. Data cannot be accessed directly by the processor. It is first copied from secondary memory to primary memory. Only then CPU can access it. Secondary or external storage devices have a much larger storage capacity and the cost of secondary memory is less as compared to primary memory.
Secondary memory is a physical device for the permanent storage of programs and data, such as read-only memory (ROM), flash drives, hard disk drives (HDD), magnetic tapes and other types of internal/external storage media.
Not all computers require secondary storage. Embedded computers, such as those found in a washing machine or central heating system, do not need to store data when the power is turned off.
Secondary Memory (non-volatile memory)
