Monday, 14 May 2012

Hardware : Storage

Information and documents are stored in computer storage so that it can be retrieved whenever they are needed later on.
Computer storage is the holding of data in an electromagnetic form for access by a computer processor.

Computer storage is important to help users store programs and data to be used at a later time.
It is also useful to keep current data while being processed by the processor until the information is saved in a storage media such as a hard disk or a diskette.
Computer storage also stores instructions from a computer program.


Primary storage is known as the main memory of a computer, including RAM (Random-Access Memory) and ROM (Read-Only Memory). It is an internal memory (inside the CPU) that can be accessed directly  by the processor.

Secondary storage is the alternative storage in a
computer. It is an external storage that refers to various ways a computer can store program and data.

  • Primary storage is installed internally. Two main types of primary storage are RAM and ROM.
  • Data from RAM can be read or retrieved and written or stored during processing whereas data from ROM can just be read only.
  • RAM is volatile, which means the program and data will be lost when the
  • computer is turned off.
  • ROM is non-volatile which means it holds the programs and data even when the computer is turned off.
  • Many complex functions, such as translators for high-level languages and
  • operating systems are placed in primary storage.
 volatile  : The content is lost when a computer’s power is turned off.


There are two types of primary storage which are RAM and ROM.
  1. RAM is an acronym for Random-Access Memory which means the data and program in RAM can be read and written.
  2. ROM is an acronym for Read-Only Memory. The data or program in ROM can just be read but cannot be written at all.
  • RAM is installed inside computers. RAM is also known as a working memory.
  • The data in RAM can be read (retrieved) or written (stored).
  • RAM is volatile which means the programs and data in RAM are lost when the computer is powered off.
  • A computer uses RAM to hold temporary instructions and data needed to complete tasks. This enables the computer's CPU (Central Processing Unit) to access instructions and data stored in the memory very quickly.
  • RAM stores data during and after processing.


  • ROM is another type of memory permanently stored inside the computer.
  • ROM is non-volatile. It holds the programs and data when the computer is powered off.
  • Programs in ROM have been pre-recorded. It can only be stored by the manufacturer; once it is done, it cannot be changed.
  • Many complex functions, such as start up operating instructions, translators for high-level languages and operating systems are placed in ROM memory.
  • All the contents in ROM can be accessed and read but cannot be changed.

Data and program
Stores during and after 
Stored by manufacturer
Stores information 
Stores instructions  (Information) permanently
Processing time
Very fast, but uses a lot 
of power
Fast, but uses very little power

Secondary storage is an alternative storage. It is very useful to store programs and data for future use. Secondary storage is required for two reasons.

1.   The working memory of the CPU is limited in size and cannot always hold the amount of data required.
2.    Data and programs in secondary storage do not disappear when the power is turned off.


Secondary storage is another alternative storage to keep your work and documents. It is very useful to store programs and data for future use.
It is non-volatile, which means that it does not need power to maintain
the information stored in it. It will store the information until it is erased.



Magnetic Medium is a non-volatile storage medium. It can be any type of storage medium that utilizes magnetic patterns to represent information. The devices use disks that are coated with magnetically sensitive material. The examples of magnetic storage are:

  1. magnetic disk such as:
  • a floppy disk, used for off-line storage
  • hard disk, used for secondary storage
  1. magnetic tape; including video cassette, audio storage reel-to-reel tape and others.

Optical Medium is a non-volatile storage media that holds content in digital form that are written and read by a laser. These media include various types of CDs and DVDs.

These following forms are often commonly used :

CD, CD-ROM, and DVD: Read only storage, used for distribution of digital information such as music, video and computer programs.
CD-R: Write once storage, the data cannot be erased or written over once it is saved.
CD-RW, DVD-RW, and DVD-RAM: Slow to write but fast reading storage; it allows data that have been saved to be erased and rewritten.

Optical media have a number of advantages over magnetic media such as the disk capacity. One optical disk holds about the equivalent of 500 floppy disks worth of data. Durability is another feature of optical media, they are able to last for up to seven times as long as traditional storage media.
Flash Memory is a solid-state, non-volatile, rewritable memory that functions like RAM and a hard disk drive combined. Flash memory store bits of electronic data in memory cells just like DRAM (Dynamic RAM), but it also works like a hard disk drive that when the power is turned off, the data remains in the memory. Flash memory cards and flash memory sticks are examples of flash memory.
Flash memory cards are also used with digital cellular phones, MP3 players, digital video cameras and other portable digital devices.
Flash memory is also called USB drives, thumb drives, pen drives or  flash drives, are the up-and-coming players in the portable storage market.
The advantages of flash memory are, it offers fast reading access times  among the secondary storage devices, (though not as fast as RAM) it is durable and requires low voltage. It is also light and small. The disadvantage is, it is more expensive than the magnetic disk of the  same capacity.

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