Storage is the function that reads, writes and retains data. 

The ability to store and retrieve data is the major reason why computers are able to perform multiple tasks.

Other technologies invented by man are dedicated to performing one particular task; e.g. an oven cannot be easily modified to perform as a refrigerator. Computers can in a matter of seconds change from being a word-processor to managing businesses finance. 

In this section we examine different types of storage used by computers and how they work together to efficiently carry out storage functions.

There are a variety of different storage devices used in a typical computer system. These devices are commonly classified as primary storage and secondary storage or temporary and permanent storage. 

Primary storage works closely with the processor; it is generally very fast and apart from Read Only Memory (ROM), requires power to retain its contents. 

• Primary storage is often referred to as main memory or just memory. 
• It includes the registers within the CPU, cache, physical RAM, ROM and virtual memory. 
• Apart from ROM primary memory is volatile, meaning it only temporarily holds data whilst the power is on

Secondary storage generally has a far greater storage capacity and does not require power to retain data. Both these storage types work together to carry out the storage functions. 

• Secondary storage is permanent or non-volatile storage. 
• The contents of secondary storage remains when the power is turned off. 
• Most common secondary storage devices can be classified as either magnetic, optical or solid state. 
• Examples of magnetic devices include: hard disks and magnetic tapes. 
• CD-ROMs and DVDs use optical methods for reading and, where possible, for writing. 
• Network connections, including the Internet, provide further secondary storage on remote computers. 
• In this section we consider magnetic storage and hard disk drives, optical storage and CD/DVD reading and writing, and finally flash drives which use solid state storage.