The CD-ROM disk is a thin circular piece of aluminum film. This film contains the information that the CD-ROM drive reads. This aluminum is covered with a clear plastic coating called polycarbonate> which protects the aluminum film. A label is put on top of the disk. All reading of information occurs on the bottom of the disk.

The CD-ROM disk, unlike its floppy and hard disk relatives, has one spiraling track that starts at the outside of the disk and spirals into the center. If you were to stretch this track out into a straight line it would be over three miles long! This track is divided up into sectors of 2,352 bytes each.