How Does a Compact Disk (cd) Work?

TABLE OF CONTENTS

Introduction ................................................................................................pg. 2

Factors Creating the Demand For Secondary Storage ............................pg. 2

Why Buy Optical ........................................................................................pg. 3

CD Physical Characteristics.......................................................................pg. 4

How Does a CD Work.................................................................................pg 5

What is a CD-R............................................................................................pg 5

What is CD-RW...........................................................................................pg 5

How Does A CD-RW Work .......................................................................pg. 5

Advantages of CD-RW ..............................................................................pg. 5

DVD.............................................................................................................pg 6

DVD VS. CD...............................................................................................pg 6

Glossary ......................................................................................................pg 7

Questions ....................................................................................................

INTRODUCTION

The use of optical storage continues to grow at an incredible pace. The word optical in the computer industry refers to any storage method which uses a laser to store and retrieve data from media. This term includes such devices as CD-ROM , rewritable optical, WORM, CD-R, and optical jukeboxes or autochangers.

Most of us are familiar with CD-ROM, but other terms such as rewritable optical, WORM, and CD-R, may be foreign. Rewritable optical devices use media that allows data to be written repeatedly, while WORM technology writes data permanently to disk. CD-R , stores information permanently to a compact disc and is read on low-cost CD-ROM drives. These devices are currently sold as single or standalone items.

The continuing development of optical technology has opened up many new avenues and created limitless possibilities. Migration software now allows unused data to be moved from its original location to an optical device where it resides until it is needed. Since the only thing that touches the media is the laser, it is the most durable way to store and archive data. Optical storage solutions are also used in a wide variety of applications such as document timing, records retention, backup systems, and desktop publishing.

FACTORS CREATING THE DEMAND FOR SECONDARY STORAGE

Because of its high capacity, low cost, durability, and random access to large amounts of networked information, secondary storage satisfies an essential need of data intensive organizations. This need for secondary storage arises from a number of factors:

Digital convergence. The move towards graphical user interfaces and the success of operating systems, such as Windows, Windows 95, and Windows NT, have resulted in a significant increase in the average size of a stored document. Industry estimates indicate that the average document size has grown almost tenfold (PC Magazine, 03/10/98, "To Write or Rewrite?")

The information superhighway. The explosive growth of on line services, led by the Internet, has resulted in unprecedented use of such services to reach potentially huge new customer base.

Another consideration for the need of reliable secondary storage is the increasing cost of managing storage on network servers. According to Strategic Research Corporation, as storage requirements explode, organizations are finding that the cost of managing the storage is almost four times the cost of the actual storage due to server downtime, backup procedures, and hard disk failures. Low cost secondary storage alleviates many of these additional