When Mac OS X was introduced it was a significant change from Mac OS, as it was based on Unix-like operating systems FreeBSD. NetBSD and NeXTSTEP/OPENSTEP. OS X introduced a more reliable platform and multiple applications could efficiently be run at the same time. Mac OS X 10.7 (“Lion”) was the first version to support 64-bit Intel processors. It came pre-installed on all Macs beginning in 2011.