CD-i Ready

CD-i Ready is a compact disc format for mixing audio and data content on a CD. It was developed by Phillips in 1991, based on the CD-i format. 
The CD-i Ready format uses a particular technique to get audio CD players to skip over the CD-i software and data. CD-i Ready places the software and data in the pregap of track 1 (index 0). Since most CD players assume that the pregap area contains only silence, they skip it. Because of this, CD-i Ready was presented as an alternative to CD-i (which stores data in the regular indexes of the first tracks of a disc), which was more compatible with audio CD players.
The term "enhanced CD" is sometimes used to refer to different CD formats that support a mix of audio and data content. Apart from CD-i Ready and CD-i, these formats include mixed mode CDs and the Enhanced Music CD format.