OPTICAL STORAGE DEVICES

Optical storage devices and the usefulness of optical storage media, such as the Compact Disk Read-Only-Memory (CD-ROM), Compact Disk Recordable (CD-R), Compact Disk Rewritable (CD-RW), and Digital Versatile Disk (DVD), have taken the computer industry by storm. Optical media were originally intended as a replacement for recordable cassette tapes in the music industry; but as we know, optical media offer many advantages to the data storage world and have put the beloved 1.44MB floppy disk to shame. Although optical storage devices have a much slower access time than hard drive technologies, they offer many benefits. We can store books, music, pictures, and files on optical storage media. We can watch movies with DVD technology. The possibilities are almost endless, at least until the next form of storage media comes around.

CD-ROM

A CD-ROM is an optical storage disk capable of storing large amounts of data. A typical CD-ROM can hold 600MB to 800MB of information. This is equal to the storage capacity of about 700 1.44MB floppy disks. CD-ROMs are well suited for storing graphics files, movies, and music. A CD-ROM is typically written to, or ‘burned,’ once with information provided by the manufacturers of the CD-ROM. Optical media such as CD-ROMs have information burned into them by a laser beam. Actually, the term burned is used quite loosely here. For information to be written to a CD-ROM, the actual process involves changing the reflective properties of an organic dye that covers a CD-ROM by using a laser. The data can only be written to a disk one time. Reading the data on a CD-ROM requires the use of a CD-ROM device or player.

CD-ROM players and writers can be installed internally or connected externally to a computer system. Most computers today come with an internal CD-ROM player installed. An internal CD-ROM device is typically installed as a slave device on either the primary or secondary IDE controller. An external CD-ROM device is connected to an SCSI, parallel, or USB port.

MSCDEX.EXE (Microsoft CD-ROM Extension) is a file that contains a 16-bit software driver, which enables older operating systems, such as DOS and Windows 3x, to interact with and control CD-ROM players. MSCDEX was later replaced in Windows 95 by the 32-bit CD-ROM File System (CDFS), which offered better performance.

CD-R

A CD-R is an optical form of media that allows information to be written to the CD-ROM one time and read many times by the end user. It is sometimes referred to as Write-Once, Read-Many (WORM). To create CD-ROMs using CD-R technology, you need a compact-disk recordable drive and a CD-R software program installed in your system.

CD-R technology is excellent for storing personal data and providing data backup capabilities. When purchasing such a unit and software, make sure that it has the capabilities for multisession recording. This is the ability to add files to a section of the CD-ROM that has not yet been written to. CD-R technology has become more affordable and is now commonplace.

CD-RW

CD-RW is the most popular CD technology at the present time. A CD-RW disk, with the use of a CD-ROM writing device, allows you to write information to the entire disk many times (approximately 25 times). CD-RW disks are more expensive than CD-R, but are well worth the price for the capabilities they offer. CD-RW technology will most likely be replaced by DVD technology when DVD storage advances become somewhat affordable.

DVD

DVD is quickly becoming the optical player and storage technology of choice. It has the capability to store up to 17GB of data, which is many times that of a CD-ROM, and can support several full-length motion pictures on one disk. DVD uses Motion Pictures Expert Group (MPEG) compression standards to provide its tremendous storage capabilities. Another great feature of DVD technology is that it is backward compatible with CD-R and CD-RW. This means that DVD can read CD-ROMs that you have created with CD-R or CD-RW technology.

Several types of DVD technology are available today:

DVD-ROM: This is the DVD drive installed in your computer.

DVD-R: Similar to CD-R technology, the DVD-R disk can record, or be ‘written-to’ one time. It is capable of recording up to 3.95GB of information.

DVD-RW: A DVD-based technology, this disk has the ability to be ‘written-to’ many times. It can store data on either side of the disk.

DVD-RAM: Similar to CD-RW, a DVD-RAM disk can be written to many times (approximately 100,000 times). However, a double-sided DVD-RAM can store up to 9.4GB, dwarfing the storage capacity of CD-RW and DVD-RW. DVD-RAM drives are most often backward compatible and can read most variations of both CD and DVD technologies.

Test-related Tips For Optical Devices

If a CD or DVD unit has become inoperative and you need to open the tray that holds the CD or DVD media, you can insert a pin or paper clip into the tiny hole on the front of the unit. This forces it to open the tray.

If you have inserted a music CD into your CD device and no sound is coming from the PC or connected stereo speakers, verify that the CD or DVD’s audio cable is connected to an installed sound card.

If you install a new CD-ROM, CD-RW, or DVD device into a computer and it doesn’t work after the installation, the first troubleshooting step should be to verify that the jumper settings on the device are configured properly.