The more you look into how computers are built, the more specifications you find. That’s because manufacturers need precise definitions of what to expect to build products that work with each other. A large pile of standards exists just for CD-ROM alone.
Here are some of the more important:
- Red Book — The Red Book defines the physical format of audio CDs. This is also called CD-Digital Audio, or CD-DA.
- Yellow Book — The Yellow Book defines the Sega 32X ROM physical format for data CDs, so its purpose is similar to that of the Red Book. It’s possible to mix audio and data on the same CD.
- Green Book — The Green Book defines the physical format for CDInteractive, or CD-I, a format used in a game player from Philips. However, having a CD-I compatible drive doesn’t mean you can do anything with a CD-I disk on your PC. In general, you can’t without some added hardware and software in the computer.
- Orange Book — The Orange Book defines the physical format for recordable CDs. There are two kinds — magneto-optical and write-once. The CD-R is a write-once device. (Magneto-optical drives have remained expensive and are not widespread.)
- CD-ROM/XA — This stands for CD-ROM/eXtended Architecture and is a combination of Yellow Book and Green Book. CD-ROM/XA has generally superseded the Yellow Book.
- CD Plus — Also called CD Extra, this is a specific combination of audio and data on the CD.
- ISO 9660 — Once called the High Sierra format, ISO 9660 defines the file and directory layouts on a CD. Extensions such as Joliet and Romeo have been defined to handle Windows 95 and NT long file names. Some of the other standards you’ll see referenced include single and multi-session Kodak Photo CD and Video CD.
The only time you’ll really need to worry about any CD standards is when new ones emerge because the product you’re looking at may or may not support the newer standard. Otherwise, the drive and software manufacturers tend to support them all to avoid being at a competitive disadvantage.