CD-RW

The CD-RW (Compact Disk-ReWritable^[1]) was made with a material that changed its crystal structure at different temperatures. When heated to about 200 °C, the material (silver-indium-antimony-tellurium) solidifies to a reflective polycrystalline state. When heated to 500 to 700 °C, the material returns to a less reflective amorphous state.

When CD-Rs emerged, they could not be altered after recording, so they still used CDFS. However, when CD-RWs were developed, a method of writing to the disk (packet writing) and a file system (UDF) was developed to use CD-RWs like a floppy disk (reading and writing at will). Initially, a special driver had to be installed to read and write to UDF-formatted disks. However, Microsoft's Live File System, introduced with Windows Vista, worked with UDF disks natively. However, UDF-formatted CDs tend to become corrupted more often than CDs using CDFS, so the format is rarely used.

At first, most audio equipment and CD drives couldn't read CD-RWs. However, "multiread" CD drives, which could read CD-RWs, soon dominated the market.

The recorded area of a CD-RW is difficult to see but can be seen if the disk is held at the right angle.