Discuss various storage units.

Various storage units are as follows:

1. Hard Disks — Hard disk memories store information on spinning circular platters coated with magnetic material and stacked with space between them. Magnetic heads record tiny magnetic spots on the rotating disk surface to store information.
2. Compact Disks (CDs) — Compact disks (CDs) are optical media with storage capacity up to 700 MB. They come in various forms, such as CDROM (CD-Read Only Memory), CD-R (CD-Recordable), and CD-RW (CD-Rewritable), and are relatively inexpensive.
3. DVDs — DVD is an optical storage device resembling a compact disc but with approximately 15 times more storage capacity and 20 times faster data transfer than a CD-ROM. It can hold up to 17 GB of data. DVDs come in various varieties: DVD-ROM (DVD-Read Only Memory), DVD-R (DVD-Recordable), and DVD-RW (DVD-Rewritable).
4. Pen/Thumb Drives — It uses a memory technology called 'Flash'. Flash is a 'solid state' memory i.e., it has no moving parts. It retains data even when the power is switched off.
5. Blu-Ray disc — Blu-ray is the successor to DVD. It is called Blu-ray because it uses a blue laser to read from and write to the disc. It offers significantly higher data storage in the same 12-centimeter space, with common capacities of 25 GB and 50 GB.
6. Memory Stick — A memory stick is a removable memory card used to store information in devices like digital cameras, smartphones, music players, and portable PlayStations. Capacities range from 4 GBs to 128 GBs.