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El Torito Added support to enable bootable CD-media. All bootable CDs use the El Torito standard, which is supported by the BIOS on all modern PCs.

Apple Extensions Apple’s added support for their HFS file system. Windows systems cannot read these CDs without third-party tools.

It is important to appreciate that all of these file systems are extensions, not replacements for ISO-9660. That means a single CD/DVD can have both regular ISO-9660 information and the extension. For example, it’s very common to have a CD-media that is ISO-9660 and Joliet. If you place the CD into a device that cannot read Joliet, it will still be able to read the ISO-9660 information.

CD-ROM Speeds

The first CD-ROM drives processed data at roughly 150,000 bytes per second (150 KBps), copying the speed from the original CD-audio format. Although this speed is excellent for listening to music, the CD-ROM industry quickly recognized that installing programs or transferring files from a CD-ROM at 150 KBps was the electronic equivalent of watching paint dry. Since the day the first CD-ROM drives for PCs hit the market, there has been a desire to speed them up to increase their data throughput. Each increase in speed is measured in multiples of the original 150 KBps drives and given an × to show speed relative to the first (1×) drives. Here’s a list of the common CD-ROM speeds, including most of the early speeds that are no longer produced:

Keep in mind that these are maximum speeds that are rarely met in real-life operation. You can, however, count on a 32× drive to read data faster than an 8× drive. As multipliers continue to increase, so many other factors come into play that telling the difference between a 48× and a 52× drive, for example, becomes difficult. High-speed CD-ROM drives are so inexpensive, however, that most folks buy the fastest drive possible—at least installations go faster!

CD-R

Making CD-ROMs requires specialized, expensive equipment and substantial expertise, and a relatively small number of CD-ROM production companies do it. Yet, since the day the first CD-ROMs came to market, demand has been terrific for a way that ordinary PC users could make their own CDs. The CD industry made a number of attempts to create a technology that would let users record, or burn, their own CDs.

In the mid-1990s, the CD industry introduced the CD-recordable (CD-R) standard, which enables affordable CD-R drives, often referred to as CD burners, to add data to special CD-R discs. Any CD-ROM drive can then read the data stored on the CD-R, and all CD-R drives can read regular CD-ROMs. CD-R discs come in two varieties: a 74-minute disc that holds approximately 650 MB, and an 80-minute variety that holds approximately 700 MB (see Figure 13-21). A CD-R burner must be specifically designed to support the longer 80-minute CD-R format, but most drives you’ll encounter can do this.

Figure 13-21 A CD-R disc, with its capacity clearly labeled

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NOTE Some music CD players can’t handle CD-R discs.

CD-R discs function similarly to regular CD-ROMs, although the chemicals used to make them produce a brightly colored recording side on almost all CD-R discs. CDROM discs, in contrast, have a silver recording side. CD-R technology records data by using special organic dyes embedded into the disc. This dye is what gives the CD-R its distinctive bottom color. CD-R burners have a second burn laser, roughly ten times as powerful as the read laser, that heats the organic dye. This causes a change in the reflectivity of the surface, creating the functional equivalent of a CD-ROM’s pits.

Once the CD-R drive burns data onto a CD-R, the data cannot be erased or changed short of destroying the disc itself. Early CD-R drives required that the entire disc be burned in one burn session, wasting any unused part of the CD-R disc. These were called single-session drives. All modern CD-R drives are multisession drives so you can go back and burn additional data onto the CD-R disc until the disc is full. Multisession drives also have