These are optical devices. The storage medium is a 12-centimeter disk that has one spiral track on which data are stored. If this track is stretched, it will extend to over 5 kilometers. Types of CDs and CD drives are CD-read only memory (CD-ROM), CD-recordable (CD-R), and CD-rewritable (CD-RW). The typical capacity of discs ranges from 650 to 700 MB. All discs are single sided (data can be only stored on one of the two disk sides). Drives and disks usually support multiple speeds. Speeds are expressed as 24x, 36x, 52x, and so on, where x is the baseline speed and it corresponds to being able to transfer 150 KB of data per second. |
