Compact disc

A compact disc, or CD for short, was a device originating on Earth in the 20th century that was used to store digital data, such as audio recordings and computer files. Late 20th century computers were equipped with special drives known as CD-ROMs to read compact discs.

After Enterprise defeated Vosk on 1944 Earth of an alternate timeline, a compact disc being inserted into a computer's CD-ROM drive was among the images seen within the re-setting timestream.