CertiGuide to A+ (Core Hardware)  9  Chapter 0110:  Removable Media       9  IV  CD-ROM

Other Performance Factors 1 CD Digital Audio (CD-DA)

The most critical and confusing (of course) aspects of using a CD-ROM is the various different formats used to write data. Unlike a hard drive or floppy disk, there's really no way to 'format' a CD-ROM disk. There's also really no way of partitioning the disk. The differences lie in how the data is organized on the disk.

For example, a CD audio disc uses bits and bytes to store data. However, this method is completely different from the way information is written to a CD-ROM disk that stores PC data. They are encoded in two separate formats.

The first major difference in formats is whether a disk is recorded in single-session or multi-session. The reason that is so troublesome for many users is that many older CD-ROMs only supported single-session disks.

With a single-session disc, all of the data that is ever going to be stored on that disk is placed there when it is manufactured.

In a multi-session disc, one session of data can be recorded and then added to later. A simple analogy is that a single-session disk is like one book. The book begins with the table of contents and is followed by the body text. A multi-session disc would be like a library of books where there are multiple sets of text preceded by a table of contents for each body of text.

Some older CD-ROM drives only supported single-session disks. To further complicate matters, some CD-R drives will only support single-session disks.

However, all CD-RW drives are multi-session compatible. A single-session CD-ROM drive will simply not recognize a multi-session disk.

To complicate matters further, there is a myriad of different encoding formats that can be used to write data onto a disk, whether it be single or multi-session. The most commonly used formats are:

• CD Digital Audio (CD-DA)
  
  
• ISO 9660 “High Sierra”
  
  
• CD-ROM XA

Other Performance Factors 1 CD Digital Audio (CD-DA)