The main OS for Mac can be found on a Mac when it is switched on. The current main OS is called Mac OS X.
Mac OS Extended Journaled
I have a Mac OS X but I know Mac OS is a computer made by the brand/company, Apple.
The second name of Mac OS X v10.4.5 is Mac OS X v10.4 Intel.Mac OS X 10.4 was known as Mac OS X Tiger.
You cannot without erasing your hard drive and installing Mac OS 9 from scratch. Even then Mac OS 9 may not run on modern Mac hardware because Mac OS 9 needs the ROM chip to boot. Modern Mac OS X hardware uses EFI to boot the system instead of a ROM chip to boot. Mac OS X v10.0 - Mac OS X v10.4 support Mac OS 9 applications and can run them, you just need to install the Mac OS 9 compatibility program which can be found on the Mac OS X Install CD.
The oldest mac OS is System 1
Mac OS Leopard
Mac OS X 10.4 (Tiger) needs to be purchased as it is not possible to update from Mac OS X 10.2.8
Unless the disc is damaged and so needs reformatting you can run the Mac OS installer over an existing Mac OS.
Mac OS X is an operating system released by Apple Inc. It is designed for Apple branded computers, which is why you will never see a Dell, or an HP computer run Mac OS X. There are only two important versions of Mac OS X, Mac OS X Server, and regular Mac OS X. Mac OS X server was designed for servers, while regular Mac OS X was designed for most computers. The current version of Mac OS X (10.6) is named Snow Leopard.
The Mac OS comes free with a Mac. New versions have a small charge.
No. Mac OS is an operating system.
Mac OS has a graphical user interface (GUI).