MGMT 1050 Lecture Notes - Lecture 30: Blue Laser, Deportation
MGMT 1050 Lecture 30 Notes – Pitted Surface
Introduction
• A laser beam is reflected off the pitted surface of the disk as a motor rotates the disk.
• The reflection is used to distinguish between the pits and lands, and these are
translated into bits.
• On the disk itself, each 2352-byte data block, or large frame, is broken up into 98 24-
byte small frames.
• Bytes are stored using a special 17-bit code for each byte, and each small frame also
provides additional error correcting facilities.
• Translation of the small frames into more recognizable data blocks is performed within
the CD-ROM hardware and is invisible to the computer system.
• The bit-encoding method and additional error correction built into the small frames
increases the reliability of the disk still further.
• DVD technology is essentially similar to CD-ROM technology.
• The disk is the same size, and is formatted similarly.
• However, the use of a laser with a shorter light wavelength (visible red, instead of
infrared) allows tighter packing of the disk
• In addition, the laser can be focused in such a way that two layers of data can be placed
on the same side of the disk, one underneath the other.
• Finally, a different manufacturing technique allows the use of both sides of a DVD.
• Each layer on a DVD can hold approximately 4.7 GB.
• If both layers on both sides are used, the DVD capacity is approximately 17 GB.
• The use of a blue laser extends this capability even further, to approximately 50 GB.
• WORM, or write-once-read-many-times, disks were originally designed to provide an
inexpensive way for archiving data.
• WORM disks provide high-capacity storage with the convenience of compact size,
reasonable cost, and removability.
• As the name indicates, WORM disks can be written.
find more resources at oneclass.com
find more resources at oneclass.com
