Optical Storage Devices

Optical Storage Devices - CD DVD Burner -Computer Hard Drive - Data Recovery - Storage Devices - CD Rom - DVD CD - DVD Storage - CD Rewritable - CD R - CD RW 

Today, the most widely used and reliable storage devices are the optical storage devices. These devices use laser technology to store and read data to and from the disk. The most popular optical storage devices are: CD-ROM drive, DVD-ROM drive, CD-Recordable drive, CD- Rewritable drive etc. Today, all PCs also contain one CD-ROM drive. These devices use laser light to write/read data to and from the optical storage media such as CDs (compact disks). A large amount oil data, software, movies and songs etc. can be stored on a single CD. Some optical storage media is read-only while others are read and write.

An optical storage media consists of a flat, round, portable metal disc, which is coated with a thin metal or plastic or other material that is highly reflective. These discs usually are 0.75 inches in diameter and less than one-twentieth of an inch thick.

The information on the optical disk is stored in the form of pits and lands. The pits are the tiny reflective bumps that are created with laser beam. The lands are flat areas separating the pits. A land reflects the laser light, which is read as binary digit 1. A pit absorbs or scatters light, which is read as binary digit 0. The high-powered laser beam creates the pits. A lower-powered laser light reads data from the disc. Like tracks on a magnetic disk, the tracks of an optical disk are divided into sectors but shape of these sectors is different than sectors of magnetic disk.

The operating system assigns a letter to the optical storage devices that come after all the hard disks and other portable disks. For example, if a computer has one floppy drive, one hard disk, one Zip disk drive and one CD-ROM drive then letters assigned to drives will be as under:

'A' for floppy disk drive

'C' for Hard disk drive

'D' for zip disk drive

'E' for CD-ROM drive

CD-ROM

CD-ROM stands for Compact Disc Read-Only-Memory. CD-ROM is a type of optical disc that uses laser technology to store and to read data to and from the disc. A large amount of data can be stored on a single disk. Once the information is stored on the CD-ROM, it becomes permanent and cannot be changed (altered). The information can only be read for processing. Therefore, it is called Compact Disc Read Only Memory.

Now-a-days CDs are commonly used in personal computers. The CD-ROM is removable and can be used to transfer data from one computer to another like a floppy disk. The storage capacity of CD-ROM is 1000 times greater than floppy disk. A typical CD-ROM has storage capacity from 650 MD to 1GB. Today, most of the software are available on the CDs. The software companies distribute their products on the CDs. For example Microsoft Office is available on one or two CDs. Similarly, Windows operating system is also available on one CD.

CD-ROM drive 

The CD-ROM drive is used with computer to read the information from the CD-ROM. The data transfer rate of first CD-ROM used with computer was 150 KBps (Kilobytes per second). It was known as single speed drive and is denoted by X. This rate is much slower than that of a typical hard disk drive that reads data at a rate of 5 to 15 MBps (megabytes per second). Manufacturers measure the speed of all CDROM drive relative to the first CD-ROM drive. Today, CD-ROM drives have transfer rates (or speeds) ranging from 48X to 75X or more. For example, a 48X CD-ROM drive has a data transfer rate of 7,200KBps (i.e. 48 x 150 = 7200) or 7.2 MBps. It. means that the higher the number, the faster the CD-ROM drive. However, the faster CD-ROM drives are more expensive.

DVD-ROM

DVD stands, for Digital Video Disc or Digital Versatile Disc. DVD-ROM is an extremely high capacity optical disc with storage capacity from 4.7 GB to 17 GB. DVD disc is specially used to store movie films. It is also used to store huge databases, music, complex software etc.

The latest generation of DVD-ROM disks actually uses layers of data tracks; it is because the storage capacity of DVD-ROM is very high. The DVD-ROM drive or DYD player reads data from the first layer, and then look through it to read data from second layer and so on.Some DVD-ROMs are double sided. It means data is stored on both sides of the disc. A DVD-ROM looks like a CD-ROM. Although the size and shape is similar to CD-ROM but DVD-ROM stores information in different manner A DVD-ROM drive can read ordinary CD-ROM disks.

CD-R

CD-R stands for Compact Disc Recordable. It is a blank disk that is used to store information. The user can also write data on an optical disc. The process of writing data on the optical disc is called burning. A locally developed CD-R can be used in any CD-ROM drive. A CD-R is functionally equivalent to a pre-recorded CDROM. Mostly the users use the CD-R to store their valuable data and software. It must be noted that once data is written on the CD-R. It cannot be changed. However, you can store data on other part of the disk until it is full. Each part of a CD-R can be written only one time and can be read as many times. Many utility programs are available to write data on CD-R but the most popular and commonly used software for personal computers is "Nero Burning ROM". Windows has its own built-in software to write data on CD-R.

Today most of the important data is backed up on the CD-R and it is the most reliable medium. The CD-writer is used to write data on CD-R.

The main disadvantage of CD-R is that information can be written only once. These cannot be overwritten and erased. The CD-ROM is also slow in accessing as compare to hard disk.

CD-Writer

A CD-writer or recorder (or simply CD-R drive) is used to write data on CDR disks. Usually, a CD-writer can read information from CD as well as write information on CD. The locally produced CD-R disks are created with CD Writers. Today, most of the PCs have CD writer.

The speed of these drives is up to 48X or more. These drives are more expensive than ordinary CD-ROM.

CD-RW

CD-RW stands for compact Disc Rewritable. The CD-RW is a new generation of optical disk. It is erasable disc. The user can write and over-write data on the CD-RW disc many times. The CD-RW disc is also referred to as erasable CD (or CD-E). The CD-RW acts like a floppy and hard disk that allow users to write and re-write data. However, the reliability of the disc tends to decrease, each time you rewrite data.

Both CD-R and CD-RW are used for taking backup of important data from a hard disk. These are also used to create audio CDs. For example, you can record your own music or movies from purchased CDs.

CD-RW Drive

You must have a CD-RW drive to write data on the CD-RW. These drives have read and write speed is up to 48X or more but the re-write speed is 10x or more. The CD-RW drive is advanced and more expensive than CD-R drive. It can write data on both CD-R and CD-RW discs and also can read data from them. Today, most of the PCs have CD-RW drive.