Secondary memory comprises of the storage devices that are in the computer and the ones that are connected to a computer. It has a non-volatile nature hence even if the computer is turned off, it permanently stores the data. The CPU does not have the authorisation to directly access the secondary memory. Therefore, the data in the secondary memory has to be transferred to the primary memory for the CPU to access it.
Some examples of secondary memory are optical disk, pen drive and hard disk.
It is a rigid magnetic disk located within a drive unit. It stores data permanently.
It contains plastic coating. Optical disks record data digitally after which the recorded data is read with laser that scans its surface.
Pen drive is a secondary storage device that has a compact nature. To store or retrieve data, it is connected to a computer through USB.