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
Operation of CD ROM Drive
A CD-ROM drive reads a CD and displays its content on the screen. Every CD is coated with a reflective metallic aluminium alloy, which is covered with a thin layer of lacquer for protection. This aluminium metallic alloy layer stores data. This reflective metallic aluminium alloy generally found on both sides of the CD.
A CD contains thousands of spiral tracks. These tracks run from innermost area towards outside of the disc. The spiral tracks are somewhat same as grooves of a gramophone record.
A laser beam reads the data of a CD. The device that creates this laser beam is located inside the CD-ROM drive. When you insert a CD in the CD-ROM drive the laser beam shines through the protective coating of the aluminium alloy layer where the data is stored. From the aluminium alloy layer, the beam passes through an optical system which consists of series of lenses, prisms and mirrors.
A servomotor inside the CD-ROM drive positions the laser beam on the track.. After that, the laser beam reflects on a photo diode detector that converts it into a binary format, that is, in the format of 0’s and 1’s. Next the binary format is converted into ordinary language that can be understood by a user and displayed on the computer screen.