What Is a CD Drive?

A compact disc, or CD, is a thin circular piece of equipment that can be used to store data, including graphics and music. It was developed in the late 1970s and was the first mainstream way to digitally store music. The term "compact" refers to its size relative to traditional phonograph records rather than other digital formats. Standard CDs are 12 centimeters, or about 4.7 inches, in diameter.

CDs are read using a laser and a light receptor that can capture the pattern of reflections off the surface of the CD as it is rotated in a drive or audio player. Audio CDs can store up to 74 minutes of music or other sounds, and a data CD can store between 650 and 700 megabytes. At the time data CDs and drives were first introduced, they were referred to as CD-ROM drives, where ROM stood for read-only memory. CD-ROM drives could read CDs but not write them. CD-ROM capacities are hundreds of times that of floppy disks, the most common type of removable media in computers at the time CD-ROMs were introduced. The CD-ROM made new types of graphics and data-intensive software and games possible.

Audio CDs and data CDs each use standardized formats, so a modern drive can read pretty much any standard CD. Unlike cassette tapes and records, which degrade slightly with each use, a CD can theoretically be played repeatedly without data loss or corruption. Scratched or otherwise damaged CDs can be hard to play or even useless, however, and mechanical parts in CD players and CD drives can wear out. Dust in CD drives or on CDs can also cause playback problems, so it's best to keep drives closed and discs in cases when they're not in use.

Starting in the late 1990s, user-writable CDs and drives that could read and write them became widely available. People used them for data storage, exchange and back up and for music storage. When music is recorded to writable CDs using a computer, it can also be played back in compatible stand-alone players, other computers, DVD players or car CD players. This was briefly a popular way to transport custom-made collections of music, but it's since been mostly replaced by digital music players and smartphones.

There are two basic types of writable CD. There are CD-R discs, which stands for CD-recordable. These discs are purchased blank and can be written to once using a compatible drive. Once files or music are written to them, they cannot be altered with standard hardware.

A second type of recordable CD is the CD-RW, for CD-rewritable. These discs can be written more than once, so if one has data on it, it can be rewritten with a new set of files or music.

When writable CDs were new, not all drives could handle CD-RW discs, and some were faster than others at writing to CDs. Speeds were typically advertised in terms of types of discs they could handle and how much faster they could write to CDs than the standard playback rate, such as 24x CD-R drives or 36x CD-RW drives. Now, most drives that write CDs can handle both types at relatively speedy rates. Drives that can write to CDs are sometimes referred to as CD burners.

There are a few more obscure types of CD that are less frequently used. If you come across one of these types of CD, you should make sure that you have the hardware and software to play it.

These formats include CD singles, designed to store one or a handful of songs. They're usually just eight centimeters in diameter and can hold about 20 minutes of music. Many audio CD players and computer drives can play them, but you should make sure yours can so you don't damage your drive or the disc. Some are also used to store music in the popular MP3 format and, since that format is compressed, they can store about three hours of MP3 music.

Another format of CD is known as the CD+Graphics, or CD+G, format. This format was designed to allow audio CDs to be accompanied by simplistic graphics, such as song lyrics. It was seldom used and is not widely supported.

CD-Interactive, or CD-i, was a later attempt at a graphical CD format with some support for interactivity without the need for full-fledged computers. It also was never popular with consumers. Some video game systems, including the Sega Saturn and original Sony Playstation, also distributed games on CDs. While it's sometimes possible to read the files off video game CDs using a modern computer, it's usually not possible to actually play the games without compatible gaming systems or specialized emulation software.

Other, more recent, types of optical media read with lasers include _digital versatile discs, or DVD_s. These were commonly used to distribute movies for home play, using DVD players attached to televisions, starting in the late 1990s. They could also be used to store files and held up to about 8.5 gigabytes worth of data, a dramatic increase from CDs. Most DVD drives and DVD players could also handle CDs.

More recently, a new format called Blu-ray disc has largely been used to distribute movies and store files. Blu-ray players, whether they're drives in computers or devices meant to hook up to a TV, can generally also play DVDs and CDs. A competing format known as HD-DVD was largely abandoned in the late 2000s, and those discs are usually not compatible with modern players.

Some computers today don't ship with any optical drives, and some movie and music fans don't have any devices that can play CDs, DVDs or Blu-ray discs.

On computers, many users have switched to USB memory sticks that can hold more data and operate more quickly than optical discs. Thanks to speedy Internet connections, people have also migrated in many cases to using cloud storage systems such as Dropbox, Microsoft OneDrive and Google Drive to store files and transfer them between devices, meaning they sometimes don't need any removable storage media at all.

When it comes to movies and music, many people prefer to use streaming services such as Netflix, Amazon Prime and Spotify. These make big libraries of music and movies available without the need to store discs and worry about discs or players getting damaged. Many modern smart TVs support streaming services without even needing special software or players. Cable providers also offer streaming, on-demand movies, sometimes included with existing packages of channels.

Whether it's a DVD, a CD or a USB stick, putting media from an unknown source into your computer can be a risk. Hackers can embed malware on such media, and depending on your system's configuration, it might immediately infect your system or do so when you access files on the drive. If you're not sure where a disc or USB stick came from, it's often best to keep it away from your computer.

If you're going to stick a CD or another type of disc in a drive or player, it's also a good idea to inspect it for dust or debris, which could scratch the disc or damage the player when you use it. If you spot dust, carefully wipe it off with a soft cloth.