The bottom plastic layer has grooves pre-pressed into it, to guide the laser along the correct path. The write laser moves in exactly the same way as the read laser: It moves outward while the disc spins. There is a mechanism that spins the disc and another mechanism that slides the laser assembly. The machinery in a CD burner looks pretty much the same as the machinery in any CD player. When the beam passes over a bump, the light is bounced away from the optical sensor. When the laser passes over a flat area in the track, the beam is reflected directly to an optical sensor on the laser assembly. To read this information, the CD player passes a laser beam over the track. The bumps and flats are arranged in a continuous track that measures about 0.5 microns (millionths of a meter) across and 3.5 miles (5 km) long. In conventional CDs, these 1s and 0s are represented by millions of tiny bumps and flat areas on the disc's reflective surface. CDs store music and other files in digital form - that is, the information on the disc is represented by a series of 1s and 0s (see How Analog and Digital Recording Works for more information). If you've read How CDs Work, you understand the basic idea of CD technology. If you were to unwind this track, it would extend out 3.5 miles (5 km).

How to burn dvds on my computer