Because the operating system requires significantly fewer system ... The first IBM PCs went on sale in 1981, but this ...

Here we’ll fill you in on the names of the different versions of the Mac operating system in order: from the newest macOS to the first version of Mac OS X and the codenames that Apple used for them.

The operating system for iPhone is called iOS. It was based on Mac OS X and built for touch. Apps are distributed via the App Store, and Apple controls which apps are approved for sale.