This document discusses computer memory and storage devices. It defines storage devices as components that can read and write to storage media like CDs/DVDs. Memory can be primary (RAM and ROM) or secondary (hard disks, CDs, DVDs). Primary memory is volatile and temporary while secondary memory provides permanent storage. The document also defines units of storage like bits, bytes, kilobytes, megabytes and gigabytes. It describes different types of storage access and various backup methods and solutions.

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STORAGE
DEVICESAN 2015

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Storage Devices vs Storage Media
 A storage device
 is something that has the ability to read and write information
to and from a storage media
 Eg. CD/DVD writer
 Storage media
 The components that store the information
 Eg CD/DVDs, Hard disks, etc
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Computer memory is any physical device
capable of storing information temporarily or
permanently.
All computers have memory that is used to
hold the program instructions that the CPU
executes. The CPU can also write to and
store information in the memory.
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Memory
Primary
RAM ROM
Secondary
Hard Disk CD DVD
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Memory
PRIMARY SECONDARY
RAM ROM
To store data permanently
• Hard Disk
• CD
• DVD
Aka ‘backing storage’
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Primary Memory
RAM ROM
 is a Volatile memory
 is temporary memory
 is memory that loses its
contents when the computer is
turned off
 the more RAM a system has –
the faster it will run
 is Non-volatile memory
 is permanent memory
 is memory that keeps its
contents even if the power is
lost
 usually used to store the
essential program drivers to
start the computer
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Backing storage
 Any type of data storage device apart from RAM or ROM
 Used to store data permanently even when the computer is
turned off
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How Computer Memory Is Measured
 Bit
 All streams of input symbols to a digital system are evolved with 2
distinct symbols. These symbols are 0 (zero) and 1 (one), and are known
as Binary Digits or Bits.
 Byte
 A byte consists of eight bits
 Kilobyte
 A kilobyte (KB) consists of 1024 bytes
 Megabyte
 A megabyte (MB) consists of 1024 kilobytes
 Gigabyte
 A gigabyte (GB) consists of 1024 megabytes
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Secondary Storage Devices
[also known as . . .
. . . external memory and auxiliary storage]
Secondary storage is a storage
medium that holds information
permanently until it is deleted or
overwritten even when the computer is
turned off
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Memory Terms
 Main or Internal memory
 RAM & ROM
 Backing storage
 Any other memory other than RAM & ROM
 Serial or Sequential Access
 Data is stored in a sequential sequence so that information stored can
only be accessed by scanning through the data to that point. Eg. Tapes
 Direct or Random Access
 Any piece of information stored on a random access device can be
accessed without having to scan through its whole contents. Much
faster than serial access. Eg. CD, DVD
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Backing Up – Backup Models
 Unstructured Backup
 Selecting files
 Full System Backup
 Incremental Backup
 Backups after Full System Backup
 Off-site Backup
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Backup Solutions
 Manually copying
 Software backup
 Mirroring (RAID)
 Two or more hard discs are linked such that information is written to
both of them at the same time, creating clones
 Online or Remote backup
 Files backed up via the internet to an online server usually by a third
party software installed on computer. Cloud computing !
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Thank You 
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