Unit I : Evaluation of Computer System
Computers have become a vital part of our life. This Chapter introduces you to the computer and the way computer works. Different parts of the computer and how they work is also covered in this chapter.
Unit II : Hard Disk Drive
Unit III : Optical Media
Unit IV : Processor
Unit V : Hardware & Networking
CD Technologies (CD-R, CD-RW)
The CD-R Technology
In the CD-R technology, data on a CD can be written only once. In other words, you cannot erase the data once it is written on a CD using the CD-R Technology. The CD based on this technology is created by a CD-R drive, but such CD’s can be read by any CD-ROM drive.
The CD-R technology is also known as the Write Once Read Many (WORM) technology. You can use the CD’s created using the WORM technology for taking backups or distributing software. Such CDs have a temperature sensitive dye coating on their surface. While writing the CD, a laser beam falls on a particular area on the surface of the CD, changing the color of the area. You can see the difference in color by looking at the surface of the CD. You will notice that the area where data is written appears in a different color than the original color of the CD surface.
CD-R drives come in the IDE, SCSI and Universal Serial Bus (USB) interface models.
A disadvantage of writing data on a CD with using a CD-R drive is that if the CD-R drive does not receive data in a steady stream, an error occurs, resulting in damaging of the CD. You can avoid this problem by using a high end computer that has at least 512 MB of RAM.
Mini Disk is another type of CD which can be created using a CD-R drive. Most CD ROM drives accept a standard CD and mini disk.
The CD-RW Technology
CD-RW (also called Compact Disk Erasable) is a technology that allows you to create CDs on which data can be written multiple times. CD-RW are good for creating data backups, archiving or distribution. CD-RW CDs are written with the help of CD-RW drives and these drives can be connected with SCSI, IDE, USB or FireWire Port.
Originally the technology to write data multiple times on a CD was known as the Phase-change Dual (PD) technology, as a PD/CD drive used a normal laser beam to read a PD disk. Now a days PD/CD drive uses a high powered extensive laser to read PD Disk.
The CD created using a CD-RW drive can be read on any standard CD-ROM drive or a drive labelled with MultiRead. MultiRead or MultiRead2 is an Optical Storage Technology Association (OSTA) specification, ahich states that a CD-RW drive is compatiable with CD-ROM and CD disks.
The drawback of the CD-RW disc is that it gets damaged after multiple writes.