The metal recording surface of a compact disc, features a series of grooves and bumps. The grooves (also called lands) reflect laser light, while the bumps (also called pits) scatter the light. Reflected light strikes a photo-receptor and is read as a 'one', or 'on'. The scattered light from the pits is read as a 'zero', or 'off'. This sequence of the lands and pits represents binary code. This is imprinted by the manufacturer, and cannot be altered.
