1. How a CD-ROM Works Bill Holmes Chandler-Gilbert Community College

2. Overview CD is standard for installing computer programs Uses CD-ROM media ( C ompact D isk R ead O nly M emory)  650 Mb. capacity compared to 1. 44 Mb. for floppy disks  Pits (holes) and Lands (plateaus) store the data (1s and 0s) http://entertainment.howstuffworks.com/cd1.htmhttp://www2.h-net.msu.edu/~filmhis/resources/CD-ROM.gif

3. Parts Overview Tray motor  Ejects and pulls in CD tray Read head  Shines light on CD and reads reflection Spin motor  Spins the CD at various speeds

4. Reading Data From a CD Laser shines light on disk Pits and lands reflect light differently Reflected light is picked up by sensor Sensor changes light to electrical signal for the computer Motor moves the head to read all parts of the spinning CD. Demo: http://entertainment. howstuffworks.com/ cd2.htm http://entertainment. howstuffworks.com/ cd2.htm

5. CD Finish CD spins between 200 and 500 RPM depending on position of the head  Faster near center  Slower near edge  That way data comes off disk at same rate  Demo: bottom of http://entertainment.howstuffworks.com/cd2.htm http://entertainment.howstuffworks.com/cd2.htm Clean with soft damp cloth Handle by edges only, don’t touch surface