 Why isn't it called OS 10 anyway ? It would make a lot more sense. 

In grade school everyone learns to count to 10. As you learned a long time ago, after 8 and 9 comes the number 10. It's universally accepted, everyone knows this. So why do we have OS X instead of OS 10 ?
I don't recall ever using OS V or OS W back in the 1990's. How did this come about ?

If you're an Apple / Mac old timer you probably remember way back in the latter 80's when the Mac OS was called System Software 6. After that it eventually became System Software 7 in 1991. When Steve came back to Apple in 1997 the next name chosen was Mac OS 8. Shortly after that came, you guessed it, Mac OS 9. So why wasn't it called Mac OS 10 Cheetah back in 2001 when that was first released ? It actually was, it just wasn't a ten from the base 10 number system we all learned in school.

Apple chose to use the Roman numeral Ten, not a capital letter X. OS X is derived from the software that Steve Job's former company NeXT had created and developed since the late 1980s. Notice the capital X in NeXT. Steve Jobs / Apple wanted people to know that this was a completely different animal (cat) than the previously released Mac OS 8 and 9. The code was written independently by NeXT programmers. Apple bought NeXT to get Jobs back at Apple, more so than to gain the right to use their OS. Ironically NeXTSTEP, the NeXT software, was written to run on Intel based systems. It had to be ported to the PPC architecture to work on Macs back in 1999 / 2000.

Another reason for the Roman Numeral 10 choice was that Roman Numerals make whatever they are connected with appear special and important. They are used for the Summer and Winter Olympic games as well as the American football championship game, the Super Bowl.

So here's the take home point. The X in OS X should be pronounced "ten" and not "ex" like your ex girlfriend or ex boss. Here is the Mac OS 9 installation disk. IX = 9 in Roman Numerals and X = 10.


Here's a pic of the Cheetah OS X 10.0 DVD case, when it still looked like a classic Roman Numeral Ten.

In the next image you can see how the Roman numeral ⓧ evolved into the look of a capital letter X on successive versions of the Apple software packaging.

click image to enlarge

So now you know why there is the capital letter X I mean Roman Numeral Ten after the OS. Why haven't we gotten OS XI yet ? It's been 16 long years since OS X came out. Probably because it doesn't look as elegant as just a standalone X.

Here's a handy reference chart for those under about age 50 that never learned this in school.

It's kind of ironic that Super Bowl 50 last weekend wasn't depicted as Super Bowl L which is the Roman Numeral for 50. The majority of Americans wouldn't know that L is the same thing as the number 50.
They could've just called it SUPERBOWLL but that would have confused the masses. End of lecture.

 Mac OS X has now changed once again to just OS X. Apple dropped the "Mac" a few years ago. Is
this a clue from Apple that OS X will eventually run on tablets and phones and not just Macs ?

Just when we've figured out why OS X is called OS Ten, Apple has made yet another change and gone back to calling it macOS. It's a name they've used in the past with the System 7 software (MacOS 7.6) back in 1996. So now twenty years later they've gone back to the Mac name. As the saying goes: "The more that things change, the more they stay the same."