A full history of macOS (OS X) release dates and rates
If you search within the OS X category you should see downloads for all versions of OS X, at least from version 10.3 to 10.6. You may be able to access the Developer section of the website, but Download All versions including old versions of Mac OS X: El Capitan, Yosemite, Mavericks, Lion, Snow Leopard, and Snow. Nov 15, 2019 · How to Check if You Have the Latest Version. To see which version of macOS you have installed, click the Apple menu icon at the top left corner of your screen, and then select the “About This Mac” command. The name and version number of your Mac’s operating system appears on the “Overview” tab in the About This Mac window.
Apple Mac OS X Version 10.5.1 Leopard I knew I needed an upgrade to stay current with Apple offerings, but was very pleasantly surprised at the changes and improvements built into this retail copy of Apple's current Leopard operating system. Examples include: Improvements in wireless connections.
macOS and OS X version code-names | iMore
Apple Mac OS X Mavericks for Mac - Free download and
Unlike that old (original) operating system, macOS (since OS X) is based on the Unix operating system (current versions have UNIX 03 certification) and on technologies developed between 1985 and 1997 at NeXT, a company that Apple co-founder Steve Jobs created after leaving Apple in 1985. The "X" in Mac OS X and OS X is the Roman numeral for the Find out which macOS your Mac is using - Apple Support