Reading data from a CD-ROM

CD-ROM (Compact Disk – Read Only Memory) is a metal disc into a plastic protective housing. There is a process of creating CD and placing data on it that each disk to be mastered. CDs are Write Once, Read Many (WORM) memory, there is no way to change data on it. 

These steps are for reading from a CD-ROM: 

1. A single track runs in a spiral pattern from the Centre of disc to outside. Track is made of lands and pits to represent once and zeros of binary data. 
2. A low-powered laser is shored on a metallic surface and reflection is captured in a photodiode sensor, lands reflects differently to posts, that means it can differentiate a 0 and a 1. 
3. Disk spins and lasers follow the track. 
4. Binary data are put together and CD-ROM has been read. 
   

So, that’s how to read data from CD-ROM. 

Advantages of using CD-ROM :-

• These are not costly. 
• Data can not be written over by the consumer, that’s another advantage. 
  

Disadvantages of using CD-ROM:-

• Data can not be written over once it is written. 
• It has slow seek time. 
• Data degrades with time.