Compact disks (or CDs) are made of pits and lands noticeable as bumps on the underside of the disk, coated with a thin layer of aluminum that results in a reflective surface. Data is written in concentric circles further split up into sectors of 512 bytes, each known as tracks on the CD from inside to outside (or edge) of the disk:

• Diameter: 120 millimeters
• Type of laser used to write data: 780 nm (nanometer) infrared laser
• Maximum capacity of a CD: 650-700 MB

Various types of CDs:

• Compact Disk - Read-Only Memory (CD-ROM): This disk comes with data on it in the form of programs, games, music, and so on, and can only be read from
• Compact Disk Recordable (CD-R): Data can be written to this disk, but only once
• Compact Disk - ReWritable (CD-RW): Data can be written to this disk many times