In addition to being an online audio player, storage system, and music store, iTunes may be used as a digital-audio editor too. Developed by Apple Computer, iTunes is available free for download and is compatible with both Mac and Windows operating systems. iTunes can play back a variety of file formats including AAC, AIFF, MP3, MPEG-4, and WAV. However, it is limited to ripping compact discs and converting digital audio from one format to another.