Secondary storage

In computer storage,  secondary storage, or  external memory, is computer memory that is
not directly accessible to the central processing unit of a computer, requiring the use of computer's
input/output channels. Secondary storage is used to store data that is not in active use. Secondary
storage is usually slower than  primary storage, or internal memory, but also almost always has
higher storage capacity and is non-volatile, preserving the stored information in an event of power
loss.
Storage devices in this category include:
•  CD, CD-R, CD-RW
•  DVD
•  Flash memory
•  Floppy disk
•  Hard disk
•  Magnetic tape
•  Paper tape
•  Punch card
•  RAM disk