?Version = Major.Minor.Build
Technically they could call it anything they want, but
they usually stay pretty close to what is universally
excepted. 2000 was a major release and XP was a minor
release. 10.1.1 to 10.5.5 is still the same major
release.?
That?s the theory, yes. But, there is an old saying:
?In theory, things should work in practice the same
way they do in theory, but in practice that?s not
always true.?

You see,
marketing has messed things up here.
In the specific case of Mac OS X, Apple painted
themselves into a corner with the product name, which
depends on the version number.
Mac OS Classic ran from Versions 1 through 9. The
first seven major versions were called simply ?System
#? where ?#? was the Major Version Number according to
the pattern you described.
System 7 was the last to be named that way. The next
version was marketed as Mac OS 8 (a name that caused
some confusion among old Digital Equipment Corporation
minicomputer programmers/users such as myself who used
DEC PDP-8 minicomputers running DEC OS/8), followed by
Mac OS 9 (which caused confusion among slightly
younger programmers who had known the rather cool for
its time OS-9 multi-tasking multi-
user operating system originally available for Motorola
6809-based computers such as the Radio Shack Color
Computer 2 or 3, and other 8-bit 6809-based devices ?
it was the OS at the heart of the short-lived CDi
interactive CD set-top-box platform ? another version
called “OS-9/68k” was made for the 680x0
32-bit CPUs).
Mac OS X was a completely new OS, and really should
have been numbered starting with 1.0. But Jobs
couldn?t resist that the ?X? in Unix and X-windows,
both of which were technologies that Mac OS X either
used or could use, was also the Roman Numeral for ?ten
(10).? And the previous and last Mac OS Classic was
version 9. So the next should be 10, right? X = 10.
Indeed, to this very day, the preferred pronunciation
is ?Mac Oh Ess
Ten,?
not ?Mac Oh Ess
Ecks.?
The problem is, no matter how you look at it, this
naming / numbering scheme has nowhere to go!
If Apple sticks with the Roman Numerals scheme, what
would the next version be called? Mac OS XI? That
doesn?t look anywhere
near as cool from a
marketing standpoint, nor does it resonate as well
with Uni
X or
X11 geeks. Besides, after
awhile it would get rather unwieldy: we?d soon be at
Mac OS XVIII!
If Apple were to go with the more popular
interpretation of the ?X? simply being the
letter ?X,? then the next version would be the
considerably less-cool ?Mac OS Y? (no more resonance
with UniX, X11,
etc.) followed by ?Mac OS Z? ?
and
then what? ?Mac OS AA?? Like spreadsheet
columns past the 26th column in Excel?
Besides, all three of those would have built-in insult
puns that anti-Mac people such as yourself would just
love to pounce on: ?Mac OS: WHY!??, ?Mac OS:
ZZZzzz(snore)?, and, of course, ?Mac OS: Alcoholics
Anonymous: the OS that will Drive you to Drink!? I
think not.
Even the ?big cat? naming scheme is running its
course. The original 10.0 was code-named ?Cheetah?
(though not marketed as such) so they already used up
the
fastest of the big cats (and the fastest of
the land animals in general). Then Puma (10.1), Jaguar
10.2), Panther (10.3), and Tiger (10.4), thus using
up the strongest of the big cats already. Now we?re on
Leopard, which is slower than a Cheetah and weaker
than a Tiger, and thus a step backwards. To ?stretch?
this naming scheme, the next version is Snow Leopard,
a mere type of leopard (too bad they didn?t use
?Black Panther? ? that one?s wasted). 10.6 will be
?Lion,? thus using up the biggest of the big cats and
the one called “The King of Beasts.”
What?s left? Ocelot? Cougar? Bobcat? Siamese? Tabby?
Calico (a genetic defect)? There?s not exactly a lot
of room for improvement here, either.
While this doesn?t help the feline situation, as far
as either Roman numerals go or letters, Apple is
pretty much stuck with the number 10 as the Major
Version Number for reasons given above, even if in
reality we should be
long past that by now.
10.1 Puma pretty much
was a Service Pack, and
was in fact free to 10.0 owners. Puma was the first
actually usable version of Mac OS X, as Cheetah was
basically a buggy beta released to the general public
(which, as you well know, Microsoft also does: nobody
in their right mind ever uses
any Microsoft OS
for mission critical apps until SP1 at the earliest,
and XP didn?t become truly decent until SP2).
But none of the others are service packs. 10.2 Jaguar,
10.3 Panther, 10.4 Tiger, and 10.5 Leopard have all
added substantial functionality both to the underlying
OS and to the user interface and features obvious to
the end user,
at least as substantial as the
changes from, say, Windows 2000 to Windows XP (though,
as noted, that is also a ?dot release? that Microsoft
charged for: NT 5.0 to 5.1). I would even put them on
a par with the change from Windows NT to Windows 2000
(4.0 to 5.0).
Microsoft also has charged for what, even by
your definition, would be a service pack even
from the marketing name, at least once: Windows 98
Second Edition was a
paid upgrade to Windows 98
First Edition owners.
Frankly, though, given when the actual major changes
occurred, Windows 95B/OSR2 should really have been
marketed and sold as Windows 96 (it introduced FAT32,
a
major upgrade to its hard disk handling), and
Windows 95C/OSR2.5 should?ve been Windows 97 (or maybe
Windows 96 SE ? it introduced USB support, arguably
the most significant enhancement in usability
of computer peripherals in general since the personal
computer got started!). Windows 98SE could easily have
been Windows 99 ? to this day, you can find many
software packages that list Windows 98SE as a Minimum
System Requirement: they would work under 98SE, but
not under 98 First Edition ? strange
indeed for what is supposedly the same OS! Adobe, for
instance, recommends a different, earlier maximum
version of Adobe Acrobat Reader for 95 through 98
First Edition
vs. the one it recommends for
Windows 98SE and ME (ME really
was just a paid
service pack to 98SE from a technical POV, and a lousy
one at that).