Have you ever wondered what all those numbers mean when you go to buy a CD burner? When you see a configuration that looks like 12x2x24 (three numbers separated by the letter "x"), these numbers indicate the drive speeds of the CD drive. The "x" stands for the transfer of 150 KB of data per second, and each number represents a different action that the CD drive can take. A CD-R drive has two actions -- recording onto and reading from compact discs. A CD-RW drive has three actions -- recording, rewriting (erasing and recording over) and reading. When looking at the drive speeds, the first number ("12" in the above example) indicates the speed at which the CD drive will record data onto a CD-R compact disc. So, in the above example, the CD drive will record data at 12 times 150 KB/second. The second number ("2" in the above example) indicates the speed at which the CD drive will rewrite data onto a CD-RW compact disc. So in the above example, the CD drive will rewrite data onto the compact disc at 2 times 150 KB/second. Typically, the second number, the rewrite speed, is lower than the first number, the write speed, because rewriting is a slower process than writing. The last number ("24" in the above example) indicates the speed at which the drive will read data from a compact disc. So in the above example, the CD drive will read data from a compact disc at 24 times 150 KB/second.
CD-R compact discs are discs that can be recorded on only once. Once the data has been burned, it is permanent and cannot be erased. CD-RW compact discs are discs that can be recorded, erased and re-recorded over. Most audio CD players, especially older models, can only read CD-R discs, so it is best to record music onto CD-Rs. CD-RWs are typically used to store data or used as back up files.
For more information, see:
Recordable CD Format Overview