Apple CEO Steve Jobs and Microsoft co-founder, Bill Gates are to make a historic joint appearance at the fifth annual 'D: All Things Digital' conference.

The two men are expected to discuss the history and future of the digital revolution during an unscripted onstage chat with the Wall Street Journal's Walt Mossberg and Kara Swisher.

Both men have appeared in the 'D' conference sessions in the past, but the decision to speak freely is an unusual one.

Jobs will also appear alone during a separate segment of the event to talk about the latest developments at Apple, including the iPhone.

Additional speakers will include: Google CEO Eric Schmidt, CBS President Les Moonves, Cisco CEO John Chambers, film director George Lucas, online pioneer Steve Case, Time CEO Ann Moore, News Corp president Peter Chernin, Palm founder Jeff Hawkins, and Steve Chen and Chad Hurley of YouTube.

The event will take place 29-3 May near San Diego, California.