Prior to the introduction of the Macintosh in early 1984, Apple had several operating systems for the Apple II series, Apple SOS for the Apple III series, and Lisa OS and MacWorks XL for the Apple Lisa series; those were introduced between 1977 and 1983.
The original operating system for the Macintosh was the classic Mac OS, which was introduced in early 1984 as System Software. In 1997, System Software was renamed Mac OS.
From the release of Mac OS X 10.0 until early 2007, Mac OS X was the only software platform. In early 2007, iPhone OS was introduced, increasing the number of software platforms by one, from one to two. In 2010, iPhone OS was renamed iOS. In 2011, Mac OS X was renamed OS X. In early 2015, the number of software platforms rose by one, from two to three, as watchOS was introduced. In late 2015, tvOS was introduced, increasing the number of software platforms again by one, from three to four. In 2016, OS X was renamed macOS. In 2019, iPadOS was introduced as the derived version of iOS for iPad, increasing the number of software platforms again by one, from four to five. In 2020, macOS received an increment in its version, from 10 to 11. In 2023, the number of software platforms rose again by one, from five to six, as visionOS was introduced.[citation needed]
Starting with Lion, there is no separate Mac OS X Server operating system. Instead the server components are a separate download from the Mac App Store.
