The CDROM, or Compact Disk Read Only Memory drive is a device that
reads,writes and can decode data stored on a cdrom disc. Data is stored
on this disc in the form of tiny pits in aluminum film. The data is organized
on tracks on the cdrom in about 682 megabytes.
The CDROM uses a controller to "talk" to the PC. The Interface is the actual
connection from the drive to the motherboard or expansion slot. CDROM drives are available
in the SCSI, the IDE and Parallel-Port interfaces.
Types of Disk Storage
There are basically two types of disk storage for computers: magnetic and optical. In magnetic storage, data is recorded magnetically on rotating disks. Optical disc storage is similar to magnetic disk
storage in basic operation, but it reads and writes using light (optically) instead of magnetism.
Although most magnetic disk storage is fully read and write capable many times over, many optical
storage media are either read-only or write-once. Note the convention in which we refer to magnetic
as disk and optical as disc. This is not a law or rule but is followed by most in the industry.
At one time, it was thought that optical storage would replace magnetic as the primary online storage
medium. However, optical storage has proven to be much slower and far less dense than magnetic
storage and is much more adaptable to removable-media designs. As such, optical storage is
more often used for backup or archival storage purposes and as a mechanism by which programs or
data can be loaded onto magnetic drives. Magnetic storage, being significantly faster and capable of
holding much more information than optical media in the same amount of space, is more suited
for direct online storage and most likely won’t be replaced in that role by optical storage anytime
Optical technology standards for computers can be divided into three major types:
■ CD (compact disc)
■ DVD (digital versatile disc)
■ BD (Blu-ray disc)
All of these are descended from popular music and video entertainment standards; CD-based
devices can also play music CDs, and DVD and BD-based devices can play the same video discs you
can purchase or rent. However, computer drives that can use these types of media also offer many
Inside The CDROM Drive
The Laser Diode emits a low-level beam toward the reflection mirror. A
servo motor is activated by a microprocessor onto the tracks on the disc.
This is done by moving the reflecting mirror.
When the beam hits the disc, refracted lights is then focused through the
first lens under the disc. It is then bounced off the mirror,and directed to the
beam splitter. The beam splitter sends returning laser light to the next focusing lens. And
the last lens sends the beam to a photodetector, which converts the light
into electric pulses.
The microprocessor then decode these electric pulses and send them to
the computer through the data cable and the controller.
Components Outside The CDROM Drive
When you look inside your computer you will notice that the CDROM Drive
is mounted at the top in all tower units and may be mounted in an assembly
at the front of the Desktop PC.
As with the Hard and the Floppy Drives,the CDROM Drive processes data
with the help of the Controller which may be mounted in an expansion slot
but in most cases it will be mounted directly unto the motherboard. The drive
and controller are connected by the Ribbon Cable which allows the data to
flow back and forth as needed.
At the rear of the CDROM Drive you will see a Jumper which is used to
assigned the drive as the Master drive or the Slave drive. Since the CDROM
is can be used to play music on compact disks, the Sound Card is connected
at the rear of the cdrom drive. At the other end of this connection you will see
the Power Supply connector.
Take the time to remove the cover of your PC and get to know each and
every component. Study the location of your CDROM drive and how its
mounted in the System Unit. By doing so you will become more confident
about understanding your computer system.