Storage Devices

There are two types of storage devices. They are:

• Primary storage
• Secondary Storage

Primary Storage

Primary storage is also known as immediate access storage. There are two main types of primary storage:

• RAM - Read Only Memory
• ROM - Random Access Memory

Random Access Memory (RAM)

RAM is uses to hold data and instructions (programs) temporarily that is being worked on by the CPU. RAM is volatile (i.e. temporary/changeable). Once the computer is turned off the information that it holds will be lost.

Read Only Memory (ROM)

These are chips that hold the information necessary for starting of the computer when it is switch on (BIOS - Basic Input/Output System). ROM is non-volatile thus the information stored is not lost when the computer is turned off. The various types of ROM are:

• Programmable Read Only Memory (PROM) - This type of ROM can be programmed using special equipment. It can be written to but only once.
• Erasable Programmable Read Only Memory (EPROM) - This type of ROM can be erased and reprogrammed. EPROMs are erased by exposing it to ultra-violet light and then reprogrammed using special equipment.
• Electronically Erasable Programmable Read Only Memory (EEPROM) - This type of ROM can be erased and reprogrammed repeatedly by user. It is erased by exposing it to an electric charge. Flash memory is a type of EEPROM.

Secondary Storage

Secondary storage, also known called auxiliary or backup storage, is used to store data and instructions when they are not being processed. Secondary storage is more permanent than primary storage (main memory), since data and instructions are retained when the power is turned off. Secondary storage is also much cheaper than primary storage and is unlimited. Here are various secondary storage devices:

• Magnetic Tape
• Magnetic Disks
  1. Floppy Disks
  2. Hard Disks
• Optical Disks
  1. CD-ROM (Compact Disk-Read Only Memory)
  2. CD-R (Compact Disk-Recordable)
  3. CD-RW (Compact Disk-Re-Writable)
  4. DVD (DVD-ROM, DVD-R, DVD+R, DVD-RW)
  5. Bluray
• Flash Memory
  1. CompactFlash (CF)
  2. SmartMedia (SM)
  3. MultiMediaCard (MMC)
  4. SecureDigital (SD)
  5. Memory Stick (MS)
  6. Picture cards (xD)
• USB Drive

I/O Devices

I/O Devices - Input/Output Devices. These are devices that are used to get data and information into or out of a computer system respectively. These devices are connect to the computer and is also known as peripherals.

Input Devices

These peripherals are used to put data and information in the computer system. Here are examples of input devices:

• Mouse
• Keyboard
• Joystick
• Digitizing Tablets
• Track Pad
• Track Ball
• Light Pen
• Camera
• Scanners
• Microphone
• Sensors
• Interactive Whiteboard
• Touch-sensitive screen

Output Devices

These peripherals are used to get data and information out of the computer system to a user. Here are examples of output devices:

• Monitor (CRT or Flat Screen)
• Printer (Impact or Non-Impact)
• Plotter
• Speaker
• Projector