<P> iTunes acts as a front end for Apple's QuickTime media framework . Officially, it is required in order to manage the audio data of an iPod, iPhone, or iPad, although alternative software does exist . Users can organize their music into playlists within one or more libraries, edit file information, record Compact Discs, copy files to a digital audio player, purchase music and videos through its built - in music store (iTunes Store), download free podcasts, back up songs onto a CD or DVD, run a visualizer to display graphical effects in time to the music, and encode music into a number of different audio formats . </P> <P> In addition, users are able to add PDF files to their library . The PDFs can be synchronized with and read on several devices except the regular iPod . iTunes 8.0 saw the removal of several options in the Preferences window . For example, iTunes once gave users the option to display arrows beside the selected song's title, artist, album, and genre that link directly to the iTunes Store . These arrows are no longer removable, except through the direct editing of a preferences file . </P> <P> iTunes keeps track of songs by creating a virtual library, allowing users to access and edit a song's attributes . These attributes, known as metadata, are stored in a binary library file called iTunes Library, which uses a proprietary file format ("ITL"). It caches information like artist and genre from the audio format's tag capabilities (the ID3 tag, for example) and stores iTunes - specific information like play count and rating . iTunes typically reads library data only from this file . A second file can also be created if users activate a preference; the iTunes Music Library. xml file is refreshed whenever information in iTunes is changed . It uses an XML format, allowing third - party apps to access the library information (including play count, last played date, and rating, which are not standard fields in the ID3v2. 3 format). Apple's own iDVD, iMovie, and iPhoto applications all access the library . If the first file exists but is corrupted, such as by making it zero - length, iTunes will attempt to reconstruct it from the XML file . Detailed third - party instructions regarding this can be found elsewhere . Beginning with iTunes 10.5. 3 this behavior has been changed such that the XML file is not read automatically to recreate the database when the database is corrupted . Rather, the user should load the iTunes Library. xml file via File> Library> Import Playlist...</P> <P> It has also been noted that iTunes does not automatically track changes to actual files in the library . If a file is moved or deleted, iTunes will display an exclamation mark beside the library entry and the user will need to manually amend the library record . Several third party tools address this problem . </P>

What type of audio file does itunes use