Definition

• A CD is a portable, optical disc device used to store digital information, such as music, software and other audio and digital data. CDs can be played in a CD player or a CD drive.
  
  

Process

• The surface of a CD contains a number of indentations, or pits. A CD's surface also contains lands, which is the area between each pit. The CD reader device can access the CD via a laser. The laser shines through the CD's bottom layer and sees the height differences between pits and lands as changes in light. These changes in light intensity are measured and changed into binary code, or a series of ones and zeros that a computer system can read.
  
  

Capacity

• A blank, standard CD has a diameter of 120 mm, and can hold up to 700 megabytes (MB) of digital data. A megabyte is equal to 1,048,576 bytes, or units of digital data, and 700 MB is the equivalent of approximately 80 minutes of audio.