CD-ROM XA (Compact Disc - read-only-memory, extended architecture) is a modification of CD-ROM that defines two new types of sectors that enable it to read and display data, graphics, video, and audio at the same time. CD-ROM XA was developed jointly by Sony, Philips, and Microsoft, and its specifications were published in an extension to the Yellow Book.
CD-ROM XA (for eXtended Architecture) discs contain Mode 2 sectors (areas left free for extra data by the omission of error detection and correction code) and were designed to allow audio and other data to be interleaved and read simultaneously. Formerly, images had to be loaded before the audio tracks could be played. The CD-ROM XA specifications include 256 color modes, which are compatible with PC formats and CD-I, and Adaptive Differential Pulse Code Modulation (ADPCM) audio, which is also defined for CD-I. Photo CD, Video CD and CD-EXTRA have all subsequently been based on CD-ROM XA, although it has not survived as a separate technology.