CD-ROM

In short: A CD for data instead of music. “ROM” stands for read-only memory: the content is pressed at the factory and can only be read. Typical capacity: 650 to 700 MB.

In more detail: The CD-ROM builds on the audio CD (“Yellow Book” standard) and adds extra error correction, because data must be error-free while music can tolerate small dropouts. File systems such as ISO 9660 and Joliet make the content readable on Windows, macOS and Linux.

In Depth

Use

In the 1990s the CD-ROM was the standard for software, games, encyclopaedias and multimedia programs, because one disc held as much as hundreds of floppy disks. Operating-system installers, driver CDs and magazine cover discs also came on CD-ROM.

Speed

The basic speed “1x” delivers 150 KB/s. Drives later reached 52x (about 7.8 MB/s). Because the disc spins very fast then, high factors are loud and only fully reached at the outer edge of the disc.

Successors

Larger amounts of data were taken over by the DVD, later Blu-ray, USB sticks and downloads. Older games and programs on CD-ROM often run on modern systems only with emulators or compatibility settings. How reading works is covered under optical drives.

See also: CD, DVD, Optical drives