OS X - What is Your Operating System?
How to tell what operating system you have...
First, check the apple in the top left of your screen.
A vivid multicolored striped apple means you have OS 9 or less.
A blue apple indicates X.1 to X.4
A dark grey apple indicates X.5 or higher.
To confirm this, go to Apple menu>About this mac. There you will see exactly version of operating system you have.