CD+RW

CD Re-Writable's are a type of CD that can be written to multiple times over the course of it's life. Unlike the CD-R, the CD-RW's reflective layer is made from silver-indium-atimony-tellurium. This material is special as in its normal state, it is a reflective, crystalline material, however when heated by the writing laser at full power, it will melt and become amorphous. The amorphous spots serve as the 'bumps' in normal CD's reading '0' and the reflective spots serve as the 'trenches', reading '1'.

CD-RW was introduced in 1997 and was preceded by the never released, CD-MO. The CD-RW requires a more powerful laser than previous CDs and so it may not work on some CD-ROMs released prior to 1997.