Cache memory:

The cache is a very high speed, expensive piece of memory, which is used to speed up the memory retrieval process. The idea of introducing a cache is that, this extremely fast memory would store data that is frequently accessed and if possible, the data that is spatially closer to it. This helps to achieve the fast response time.

Random-access memory / main memory:

RAM is a volatile memory, which me Answer: that the information stored in it is not permanent. As soon as the power is turned off, whatever data that resided in a RAM is lost. It allows both read and write operations.

Hard Disk:

Hard disk is a magnetic disk on which we can store computer data. In general, hard disks are less portable than floppies, although it is possible to port by removable hard disks. Two types of removable hard disks are disk packs and removable catridges.

Compact disk: 

A CD or CD-ROM is made from 1.2 millimeters thick, polycarbonate plastic material. A thin layer of aluminium or gold is applied to the surface. CD data is represented as tiny indentations known as “pits” , encoded in a spiral track moulded into the top of the polycarbonate layer. The areas between pits are known as “lands”. A motor within the CD player rotates the disk. The capacity of an ordinary CD-ROM is 700MB.

Digital versatile Disc (DVD): 

A DVD (Digital Versatile Disc or Digital Video Disc) is an optical disc capable of storing up to 4.7 GB of data, more than six times what a CD can hold. DVDs are often used to store movies at a better quality than with a VHS. DVDs can also have interactive menus and bonus features such as deleted scenes and commentaries. Like CDs, DVDs are read with a laser.