Foundations for Interactivity,

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Storage

• Foundations for Interactivity,
• Multimedia, Knowledge

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Storage

• Primary Storage also known as main memory,
  internal memory, or RAM, is a working storage
  that holds
• data for processing
• instructions for processing the data
• processed data that is waiting to be sent to an
  output or secondary-storage device
• Secondary Storage consists of devices that store
  data and programs permanently on disk or tape.
  Secondary storage is nonvolatile that is, data
  are permanent, or remain intact when the power is
  turned off .

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DATA HIERARCHY

• Character a single letter , number , or special
  character such as _at_.
• Field a unit of data consisting of one or more
  characters.
• Record is a collection of related fields.
• File a collection of related records.
• Database a collection of interrelated files.

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Compression And Decompression

• Compression is a method of removing redundant
  elements from a computer file so that it requires
  less storage space.
• Compression and decompression techniques are
  often called codec techniques.
• The two principal compression techniques are
  lossless and lossy.
• Lossless compression techniques achieve
  compression by avoiding repetition but still
  preserving every bit of data that was input.
• Lossy compression techniques permanently
  discard some data during compression.

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JPEG MPEG

• Still images -- JPEG A lossy technique
• The JPEG codec looks for a way to squeeze a
  single image , mainly by eliminating repetitive
  pixels, or picture element dots, within the
  image .
• Moving images -- MPEG
• MPEG1 Provides VHS-like quality of images.
• MPEG2 Provides digital-TV-quality video for use
  with cable network.
• MPEG4 For wireless videoconferencing.

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Compression
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Rating Secondary-Storage Devices

• Storage capacity
• Access time the average time needed to locate
  data on a secondary memory storage device.
• Transfer rate the speed at which data is
  transferred from secondary storage to main
  memory.
• Size
• Cost

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Diskettes

• 31/2 inches The smaller size,now by far most
  common,is 31/2 inches across.
• 51/4 inches The older and larger size is 5/14
  inches across.

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Diskette Anatomy
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Diskette drives
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Characteristics of Diskettes

• Tracks and sectors data is recorded in rings
  called tracks. Each track is divided into eight
  or nine sectors.
• Data capacity
• Side There are single-sided and double-sided
  capacity.
• Density There are single, double, and
  high-density disk.
• Unformatted and formatted disks Unformatted
  disks are manufactured without tracks and sectors
  in place. Formatting means that you must prepare
  the disk for use so that the operating system can
  write information on it .
• Write-protect features It allows you to protect
  a diskette from being written to .

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Removable High-Capacity Diskettes

• EZ135
• Zip 100MB
• Jazz 1, 2 GB
• MO 230MB, 640MB, 1.3GB
• LS120 120MB

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Hard-Disk Technology for Large Computer Systems

• Removable packs This system contains several
  hard disks aligned one above the other in sealed
  unit. All tracks with the same track number,
  lined up one above the other, thus form a
  cylinder.
• Fixed-disk drives They are high-speed,
  high-capacity disk drives that are housed in
  their own cabinets. Although not removable or
  portable, they generally have greater storage
  capacity and are more reliable than removable
  packs.
• RAID (Redundant Array of Inexpensive Disks)
  storage system This system, which consists of
  several disk drives within a single cabinet,
  sends data to the computer along several parallel
  paths simultaneously.

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Overview of RAID Levels

• Level 0, striping striping data across multiple
  disks without any redundant information.
• Level 1, data mirroring maintaining duplicate
  sets of all data on separate disk drives.
• Level 3, Striping and Parity data is striped
  across a set of disks. In addition, parity is
  generated and stored on a dedicated disk.
• Level 5, Striping and Parity both parity and
  data are striped across a set of disks.

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Disk packs and cylinders
All tracks with the same track number,lined up
one above the order,thus form a cylinder.
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Hard disks
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Speeding Up Slow-Running Hard disk

• Fragmentation
• a data file becomes spread out across the hard
  disk in many noncontiguous clusters.
• Defragmentation
• data on the hard disk is reorganized so that data
  in each file is stored in contiguous clusters.

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Power Portability

• Miniaturization
• External hard-disk drives
• Hard-disk cartridges

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Optical disks
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Optical Disks
Optical disks are removable disks on which data
is written and read through the use or laser
beams.

• CDROM can hold data up to 650MB, with a data
  transfer rate 150KB/sec single speed.
• CD-R compact disk-recordable,cant be erased.
• CD-RW compact disk rewritable.
• WORM Disk write once, read many. A technology
  similar to CD-R, but is a bit older and more
  expensive.
• DVD A single DVD (Digital Versatile Disk, was
  Digital Video Disk) can hold 4.7 GB on a single
  side, single layer disk. A double layer double
  side DVD can store 17GB data.

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CD-ROMCompact disk read-only memory

• Entertainment and games
• Music,culture,and films
• Encyclopedias,atlases,and reference works
• Catalogs
• Education and training
• Edutainment
• Books and magazines

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Photo CD

• A technology that allows photographs taken with
  an ordinary 35-millimeter camera to be stored
  digitally on an optical disk.

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DVD DVD-ROM

• More storage capacity, faster data transfer
• Better audio
• Better video
• DVD-ROM and recordable and rewritable capabilities

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Flash-memory Cards and Magnetic tape

• Flash-memory cards consist of circuitry on
  credit-card-size cards that can be inserted into
  slots in a microcomputer.
• Magnetic tape is thin plastic tape on which data
  can be represented with magnetized spots.
• Cartridge tape and DAT are used to back up data
  from a microcomputer hard disk onto a tape
  cartridge.

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Magnetic Tape

• Representing data on magnetic tape
• Magnetic-Tape units for large computers
• Cartridge tape units

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The Future of Secondary Storage

• Advanced Compression Schemes
• Wavelet compression
• Fractal compression
• Compression by object-oriented programming
• compression using neural networks
• CD-ROM Jukeboxes
• Higher-Density Diskettes
• Digital VCRs Video disk Players
• Video Severs
• Molecular ElectronicsStorage at the Subatomic
  Level

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Three levels of multimedia specifications