CD-ROM images

Caddy Load and Tray Load

Earlier CD-ROM drives used a caddy. The disc must be inserted into the caddy, and the caddy inserted into the drive. Today, CD-ROM drives are caddyless. The disc is placed into a tray.

Reading a CD-ROM

Digital data are carved into the CD-ROM as pits (low spots) and lands (high spots). As the laser shines into the moving pits and lands, a sensor detects a change in reflection when it encounters a transition from pit to land or land to pit. Each transition is a 1. The lack of transitions are 0s. There is only one laser in a drive. Two are used here to illustrate the difference in reflection.

More CD-ROM images

Learn more about CD-ROM