COMPUTER MEMORY

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COMPUTER MEMORY DATA STORAGE
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ROM

• ROM is short for Read Only Memory.
• It is permanent, long-term memory which cannot be
  erased or changed in any way
• It is also known as Non-Volatile Memory because
  it doesnt disappear after the computer is
  switched off.

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ROM contd

• ROM chips instruct the computer how to load the
  operating system from the hard drive into the
  computers memory.
• Dont confuse the hard drive with ROM the hard
  drive is an internal backing store (storage
  device).

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RAM

• RAM (Random Access Memory) is-
• Temporary, short-term working memory
• Only works when the computer is turned on
• It is also known as Volatile Memory because
  data disappears if the power is switched off.
• Each time you start a program e.g. MS Word, it is
  loaded into RAM.
• The amount of RAM influences processing power,
  speed and how many programs can run at the same
  time.
• Many computers are now sold with 128 or 256 MB of
  RAM.

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Measurement of Memory

• Computer memory is measured in bytes.  A single
  byte is made up of a series of 1's and 0's, which
  are known individually as binary digits or
  bits. 
• This is the way the computer communicates and
  stores information.  With each keystroke or
  character a byte of memory is used.
• 8 bits 1 byte
• 1024 bytes 1 kilobyte
• 1024 kilobytes 1 megabyte
• 1024 megabytes 1 gigabyte

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Data Storage - Internal Backing Store

• Hard Disks are the main internal backing store
  usually found inside computers.
• The main benefit of hard drives is that they have
  a large storage capacity 20 gigabytes or more.
  (1 Gb 1024 Mb).

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External Backing Store

• Floppy disks are a common external backing store,
  however only store up to 1.44 Mb of data.
• When are they useful?
• Excellent for transferring small files of data
  from one machine to another and for backing up
  important small files stored on your hard disk.

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External Backing Store

• CD-ROM (Compact Disk Read Only Memory) disks are
  optical disks that use the same technology as
  musical compact disks.
• They store up to 700 Mb of data and a laser beam
  is used to read the data off the disk.
• What can they be used for?
• As CD-ROMs are much bigger than floppy disks,
  they can be used for multimedia applications such
  as encyclopaedias and can store pictures, sounds
  and video clips.

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3.5 inch Floppy Disk
Head Contact Area
Positioning Drive Hole
Metal Hub
Centre Hole
Disk inside plastic case
Write Protect Notch