CDROMs, DVDs, and Video Disks

1
CD-ROMs, DVDs, and Video Disks

• Media for external storage and transport of
  data
• Compact diskread-only memory
• Rewritable compact disk (CD-RW)
• DVD
• Video disk (laser disk) analog format

2
CD-ROMs

• Digital format
• Write once, read many times
• A rewritable version (CD-RW) is available, and in
  common use today
• Information is written by burning tiny holes in
  the disk surface with a laser
• The hole pattern is read by a laser and
  inter- preted as the bits comprising the data
• Can store 600-700 megabytes of data
  about 300,000 pages of double-spaced text,
  or more than an hour of high fidelity sound

3
Creating Multimedia CD-ROMs

• Requires a hard disk large enough to store 650
  megabytes of data to be written to the CD
• Requires a CD-ROM recorder that writes the data
  to the blank CD using a laser
• The developer creates the multimedia material,
  stores it on the hard disk, and then tests it as
  completely as possible
• When the material is in final form, it is written
  to the blank CD as if it were being copied from
  one disk to another

4
Video Disks orLaser Disks

• Much larger than a CD-ROM 12 in diameter
• Hold 54,000 video frames per side
• Hold 30 minutes of video per side
• Read-only
• Analog format
• Requires a conversion board to be used with a
  computer
• Excellent for large-scale, video-based multimedia
  projects