OS X Mavericks powered half of all Macs that went online in March, the largest percentage of any individual version of Apple's operating system since 2009's Snow Leopard, statistics show. Mavericks, which carries the numerical designation of OS X 10.9, accounted for 49.5 percent of all Mac operating systems tracked by Web analytics company Net Applications last month. The six-month-old operating system gained about 4 percentage points in March, slightly more than the month before.