Is it true apple computers use a Macintosh operating system?

No. Apple computers use two main OS systems depending on the CPU. These systems are called iOS and OSX.

Macintosh is a brand name used for some Apple computers. A Macintosh, a Mac, And a MacBook Pro all use OSX. The iphone, iPod Touch, and ipads all use iOS. iPod classics use a different OS called Pixo OS.