CD (compact disc) and DVD (digital versatile disc) are media for storing information. In that regard, they’re like any other type of disks like floppies, Zip disks, and hard disks. But unlike those other types of disks, CDs and DVDs are optical media, not magnetic media. That means they use a laser rather than a magnet to read and write data to and from the disk. When you copy information to a CD or DVD, the laser essentially burns the data to the disk. That’s why copying files to CDs is commonly referred to as burning to the disk. Copying files to CDs and DVDs is much slower and a lot more complicated than copying to magnetic media like jump drives and floppies. If you’re new to all of this, brace yourself for the complicated world of CDs, DVDs, ISO format, File System (UDF) format, and other bizarre new concepts.

Understanding CDs and DVDs

Even though CDs and DVDs look exactly alike, there’s a big difference in capacity. A CD holds about 650–700 MB of data. A DVD holds about 4.7 GB (or 4,700 MB). In other words, one DVD can hold more information than half a dozen CDs. This is also why albums are sold on CDs and movies on DVDs—there isn’t enough room on a CD to store a feature-length movie. As though to complicate matters, many different kinds of CDs and DVDs are available, including CD-ROM, CD-R, CD-RW, DVD-R, DVD-RW, DVD+R, DVD+RW, and DVD-RAM. So let’s untangle that mess, starting with the most common types of disks—the CD-ROM and DVD-ROM.

CD-ROM and DVD-ROM

The ROM in CD-ROM and DVD-ROM stands for read-only memory. The term “read only” means you can read (or play) the contents of the disk whenever you want. The disk is not writeable. You can’t add new files to the disk, remove files from the disk, or change files that are already on the disk.

CD-R, DVD-R, and DVD+R

The R in CD-R, DVD-R, and DVD+R stands for recordable. These are often referred to as distribution media because they’re the blank disks that software companies, record companies, and the movie industry use to stamp out thousands of copies of the programs, albums, and movies they sell. In other words, they buy –R disks to create the –ROM disks that they sell you.

CD-RW, DVD-RW, DVD+RW

The RW in CD-RW, DVD-RW, and DVD+RW stands for read/write. The -RW disks are often called backup media. You can use a CD-RW, DVD-RW, or DVD+RW disk to back up important files. You can erase the disk and start over if you like. And you can delete individual files. In short, the RW disks are much more like floppies and jump drives. Just not as fast!

Data CD versus audio CD

CDs come in two capacities, commonly referred to as data CDs and audio CDs. A data CD has a capacity of about 650 MB, or enough space to store about 74 minutes worth of music. Those are best to use when your goal is to use the CD to store backup copies of files on your hard disk, or to distribute copies of files to other people. An audio CD has a capacity of about 700 MB, or enough space to store about 80 minutes worth of music. Those are best to use when you want to create your own custom music CDs to play in your car stereo or in a CD player. You use Windows Media Player (Article 23) to create those custom music CDs.

DVD– versus DVD+

DVD is a relatively new medium, and there are still different factions warring over exactly how they should be used. The differences have little to do with DVDs as used in computers. They’re more subtle differences having to do with how DVDs store data for watching movies on TV. So for the average computer user, choosing between a + and – DVD is largely a matter of knowing what works with your DVD player, DVD burner, and whatever other equipment you have.

The only way to find out which types of disks your DVD equipment can handle is from the documentation for that specific equipment. As a rule, the DVD+ disks are compatible with more DVD players than the DVD-R disks.

Disc, Disk, What’s the Diff?

The only difference between a “disk” and a “disc” is the spelling. Computer people usually spell it “disk.” The people who invented CDs and DVDs decided to spell it “disc.” But no matter how you spell it, it’s a medium on which you can store information. I’ll use “disc” in places you’re likely to see it spelled that way. Otherwise I’ll stick with “disk” only because that’s the way you’ll see it spelled in other places throughout the article.

DVD Variations

In addition to the types of DVDs described so far, there’s DVD-RAM (random access memory), mini-DVD (small DVD disks used in some video cameras), and Double-Layer DVD (which doubles the capacity to 9.4 GB). There are also different modes to which you can store video on DVD. For example, a DVD recorder might use VR (Video Record) mode to record video. To use those disks in a computer, you have to close or finalize the disk. Things like the VR mode, closing and finalizing disks, and so forth vary greatly from one product to the next. There are hundreds of products on the market. There is no simple one-rule-fits-all that I can give you here that will tell you exactly how to work your equipment. The only way to learn about the equipment you own is to read the instructions that came with that equipment.

X marks the speed

CDs and DVDs have a basic spin speed referred to as 1x. If you listen to a CD that’s spinning at faster than 1x, it sounds like the Chipmunks. If you watch a movie that’s spinning faster than 1x, you get fast motion. You can record a disk at faster than 1x. Doing so means it takes less time to make the CD or DVD. For example, at 1x it would take 80 minutes to fill an 80-minute audio CD with music. At 16x it takes 1/16th that amount of time, about 5 minutes. The resulting disk will still play at 1x so it sounds normal. The 16x speed applies only to how long it takes to create the disk. Every CD drive and DVD drive has a maximum speed at which it can spin a disk, indicated by the x. For example, a CD burner rated at 48x can spin a CD at 48 times its normal speed. Hence, it can create a disk in 1/48th the amount of time it takes to play the disk. Blank CDs and DVDs also have a top recommended speed. If you want to take full advantage of your CD or DVD burner’s speed, find blank disks that have the same (or better) x rating as the drive.

Disk and drive compatibility

Buying CDs and DVDs that already contain music or a movie is easy. You just go to the store and buy the album or movie of your choice. Of course, you need a stereo or CD player to listen to commercial CDs. And you need a DVD player and a TV to watch DVD movies. But you don’t have to worry about all the different types of disks. When buying blank disks to make your own CDs or DVDs, things are a little more complicated. First, you need to know the capabilities of the CD/DVD drive in your computer. This isn’t always easy because most people buy computers without even realizing there’s a difference.

What Kind of Drive Do I Have?

Getting information about your CD/DVD drive isn’t quite as easy as you might expect. You might be able to get some information right from your Computer folder. First make sure there isn’t a disk in the drive. Then open your computer and take a look at the icon for the empty drive. The icon and description may provide

some clues. You can right-click that icon, choose Properties, and click the Hardware tab for more specific information.

Unfortunately, knowing the make and model of the drive doesn’t tell you all the different types of disks it can handle. For instance, the Sony DRU-510A example shown previously can read and write virtually all CD and DVD disk types. But after you know the make and model of the drive, you can search the manufacturer’s Web site for the model number for more detailed specs. Or you can use a general search engine like Google to search for both the make and model name (Sony DRU-510A in my example) and hope you don’t get too many irrelevant links. Of course, there’s always the old-fashioned method of calling your computer manufacturer on the phone, or contacting them by e-mail, and asking about the drive. At the very least, you’ll need to know the model of your computer. Then ask them what kinds of disks the drive can handle. This route may take some patience maybe even some money.

Using Disks that Already Contain Data

Using disks that already have information on them isn’t too tough. Starting with the basics, if you have a DVD drive, you can read (use) both CD and DVD disks. If you have a CD drive, you can only use CD disks. Playing the kind of CD that you buy in a music store is usually pretty easy. You stick the CD in your CD drive and, most likely, Windows Media Player will play it for you. To copy songs from that kind of CD, you rip the CD in Media Player. See Article 23 for the goods on how all that works. To watch a DVD movie, you stick the DVD in your DVD drive and hope it plays. If you have a CD drive (not a DVD drive), it won’t play at all. To copy files from DVDs, you typically have to use DVD ripping software. See “Ripping DVDs” in Article 24 for more information.

If you have Windows Media Center, that program might open rather than Media Player Movie Maker.

What kind of disk is this?

Each example is showing the same drive with a different disk in the drive. You might notice it’s referred to as CD Drive F:. It’s actually the kind of drive that can read and write many different kinds of CD and DVD disks. Windows often shows the general title CD Drive for those kinds of multipurpose drives. The look of that icon varies a lot depending on the disk that’s in drive at the moment, as follows:

- CD-ROM: The disk is a CD that contains a program I purchased. The disk has 0 bytes free because it’s a CD-ROM, and you can’t add files to a CD-ROM. (In other words, it’s not a writeable disk.) The title, PVRMCE_A50_2_4A, was put there by the company that created the disk. It’s an acronym for the name and version of the program that’s on the CD. A CD-ROM that contains only music might show only a musical note on the icon.

- CD-R: The drive contains a blank CD-R disk. All of that disk’s space is free (available for saving files). The disk has no title because I haven’t given it one yet.

- CD-RW: The drive contains a CD-RW disk titled Movie (a title I created myself). The disk has 664 MB of free space available.

- DVD: The drive contains a DVD like the kind you rent in a video store. The disk title is also the movie’s title. This is not a writeable disk as indicated by the fact that there are 0 bytes free.

- DVD-R: The disk in the drive is a DVD-R disk that’s empty. It has no title and has 4.37 GB of space available for storing files. It could also be a DVD+R disk because they’re functionally the same as DVD-R disks.

- DVD-RW: The disk in the drive is a partially filled DVD-RW disk with 2.33 GB of space left. The disk might also be a DVD+RW disk, because they’re functionally the same as DVD-RW disks.

The 4.37 GB capacity is typical, even though the official specs state 4.7 GB. That’s because the 4.7 GB rating is based on the decimal binary system. Windows shows capacities using the binary numbering system.

I’ll talk about how you copy files to the writeable disks (disks that have more than 0 bytes free) a little later in this article.

Viewing a disk’s contents

To see what’s already on the CD or DVD in a drive, right-click its icon in your Computer folder and choose Explore. You’ll see its contents in Explorer. As with folders on your hard disk, any folders on the CD appear as manila file folders. Files are represented by document icons. If the disk is empty, no icons show.

Copying files from a CD or DVD

To copy files or folders from a CD, use any method described in Article 29. But first, for those of you who skipped straight here without reading anything else, some quick reminders on when not to use the method described here: - To copy songs from a commercial CD where songs are titled Track1, Track2, and so forth, and have .cda extensions, rip the CD using Windows Media Player (Article 23). - To copy a movie from a video DVD that has a folder named Video_TS, use DVD ripping software to copy and convert to a more computer-compatible format like .avi, .mpg, or .wmv. See Article 24 for more information.

Often you can copy the .vob files to a folder on your hard disk, then change the extension to .mpg. Typically the largest .vob file is the most important one. Smaller .vob files are often just background video scenes.