CD Extra - Computer Definition
Also called "CD Plus," "Enhanced CD" and "Enhanced CD-ROM," it is a Compact Disc (CD) format that contains both audio and data. It uses the multisession capability to store up to 98 audio tracks in the first session and one CD-ROM XA data track in the second session. Audio CD players will play the first session and ignore the second. A multisession CD-ROM drive (all newer drives) will read the last session first, and the software in the data session can cause the audio session to be played. See Mixed Mode CD.