AOL Instant Messenger (AIM) is an instant messaging and presence computer program which uses the proprietary OSCAR instant messaging protocol and the TOC protocol to allow registered users to communicate in real time. It was released by AOL in May 1997. Stand-alone official AIM client software includes advertisements and is available for Microsoft Windows, Mac OS, Mac OS X, and Linux. The software, maintained by AOL, LLC, has a large share of the instant messaging market, especially in the United States (with 52% of the total reported as of 2006).