1997 Apple introduces Mac OS 8.
1997 Apple buys NeXT Software Inc. for $400 million and acquires Steve Jobs, Apples cofounder, as a consultant.
1999 Apple introduces Mac OS 9.
2001 Apple introduces Mac OS X 10.0 code named Cheetah and becomes available March 24, 2001.
2001 Apple introduces Mac OS X 10.1 code named Puma and becomes available on September 25, 2001.
2002 Apple introduces Mac OS X 10.2 code named Jaguar and becomes available on August 23, 2002.
2003 Apple introduces Mac OS X 10.3 code named Panther October 25, 2003.
2004 Apple introduces Mac OS X 10.4 code named Tiger at the WWDC on June 28, 2004.
2007 Apple introduces Mac OS X 10.5 code named Leopard October 26, 2007.
2008 Apple introduces Mac OS X 10.6 code named Snow Leopard and MobileMe at the WWDC on June 9, 2008.