How does DVD technology differ from CD?
Like CDs, DVDs store data in microscopic grooves running in a spiral around the disc. All DVD drive types use laser beams to scan these grooves: Minuscule reflective bumps (called lands) and nonreflective holes (called pits) aligned along the grooves represent the zeros and ones of digital information. But that’s where the similarities end. DVDs use smaller tracks (0.74 microns wide, compared to 1.6 microns on CDs) as well as new modulation and error correction methods. These technologies allow them to store data seven times as large as that of a CD. The narrow tracks require special lasers–which can’t read CD-ROMs, CD-Rs, CD-RWs, or audio CDs. DVD drive makers managed to solve the problem.
