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The Memory Devices

  • Memory is an essential area which is needed to store the data.
  • Without memory storage, it is not possible for the computer to perform any task.
  • It helps in storing and retrieving data.
  • There are two types of memory available
  • They are
    • Primary memory or Main Memory
    • Secondary memory

Primary Memory

  • It is used as a component, device and recording media that stores digital data used for computing, for some interval of time.
  • It is one of the preliminary components of all modern computers and merged with a CPU.
  • Semiconductor is used to store the data as a memory location.
  • There are two types of primary memories
  • They are
    • Random Access Memory (RAM): It is a semiconductor storage and fast but it is a temporary storage.
    • Read Only Memory (ROM): It is a memory unit that performs read only operation. It is a non-volatile memory. Once the program is written, if the system is shut down the data will remain in the memory. They are of many types. They are
      • PROM - Programmable Read Only Memory
      • EPROM - Erasable Programmable Read Only Memory
      • EEPROM - Electronically Erasable Programmable Read Only Memory
      • OROM - Optical Read Only Memory
Note: OROM is used to store Holographic data.

Secondary Memory Devices (Secondary Memory)

  • All computer data cannot be stored in the primary memory, where it does not have enough memory to store.
  • Hence we use the secondary storage devices to store data.
  • They are transferable, portable and easy to use
  • They are as follows
    • Hard disks
    • Floppy disks
    • Compact Disk Read only memory
    • Digital versatile disk

Hard disks

  • It is a permanent storage device.
  • It is not possible for the PC to work without this hard disk
  • It stores data in a circular platters or disks.
  • The information is stored in the surface of the rotating disk by magnetic heads as a tiny magnetic spots.
  • The following figure explains the part of the hard disk.
  • Its capacity of storage starts from 10 MB, 40 MB and so on.
  • The latest storage capacity of a hard disk is .1 GB(Giga Byte)

Note: The circular path has a set of concentric circles in the hard disk called the tracks. The track contains the data.

Floppy Disk

  • It is a portable and removable device.

  • It is capable to storage data of 1.44 Mb.

  • It stores fewer amounts of graphical data like sound, video, images and animation.

  • They are made of flexible plastic disks coated with magnetic material on both the sides.

  • For safety, they are placed inside a protective plastic envelope, which is provided with a slot for reading and writing data on the surface of the disk.

  • Data is written on the disks in the form of tiny magnetic spots.

  • The floppies have labels to identify their data contents and an index hole to indicate the starting location on the floppy.

  • The following figure shows the part of the floppy disk and its appearance.

  • There were various size of floppy disk in the olden days.

  • They are shown below.

Compact Disk (CD-ROM)

  • These players are an integral part of the multimedia development of workstation, and are an important delivery vehicle for large, mass-produced projects.
  • They are optical devices which are written in laser.
  • The data stored are Read Only.
  • Their capacity is up to 700MB
  • They are of different types
    • CD-R: Compact Disk Recordable
    • CD-RW: Compact Disk Rewritable.

Note: These devices are used to store all types of data like images, video, sounds, movie etc.

Digital Versatile Disk

  • It is an optical storage device.
  • It is also called Digital Video Disk.
  • It is mainly used for video and storage.
  • It is a multilayered disk; hence it stores more amount of information.
  • They are called as Super density disk (SD)
  • There are of many varieties. They are
    • DVD-ROM
    • DVD-R (DVD- Recordable)
    • DVD-RW (DVD-Rewritable)
Note: Blu-ray is a next generation optical device to transfer data.

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