Like 2009, this year is one of dueling operating system upgrades, when the two biggest OS rivals face off with new editions.
Now it's the turn of the numbers to tell their story.
0 The price of an upgrade to OS X Mountain Lion for buyers of new Macs who purchased their Lion-powered systems starting June 11. The program, called "Up-To-Date" by Apple, continues as long as either Apple or its authorized resellers sell Lion-equipped Macs. The free upgrade will be available from the Mac App Store after buyers fill out a form to be posted on this page of the Apple website.
It's also what a Windows user will pay for the Windows Media Center add-on after upgrading to Windows 8 Pro. The add-on, which will come with a price of some sort after Jan. 31, 2013, lets Windows 8 PCs play DVDs.
1/10th The amount a Mac owner spends to upgrade five machines compared to what a Windows user pays to do the same. Unlike Microsoft, Apple lets customers install Mountain Lion on all personally-owned machines.
1 The number of choices Windows and Mac users have for their upgrade editions.
Although Apple has long practiced one-size-fits-all, Microsoft followed suit for the first time this year when it offered only Windows 8 Pro in both the $14.99 and $40 deals. Previously, Microsoft has provided multiple upgrade versions so that, for instance, someone running Vista Home Premium upgraded to Windows 7 Home Premium, not to Windows 7 Professional.
2X How much more Windows users will pay for their upgrade to Windows 8 Pro than Mac owners will pay for theirs to OS X Mountain Lion.
3 Number of previous versions of Windows that can be upgraded to Windows 8 Pro: XP, Vista and Windows 7. That's one more than either Vista or Windows 7 covered. Vista's upgrade was available to Windows 2000 and XP machines, Windows 7 to XP and Vista PCs.
Also the amount of free space on a USB flash drive necessary to create bootable installation media for the Windows 8 Pro upgrade, useful as backup install media or to do a "clean" install by wiping the hard drive before upgrading.
5 The maximum number of Windows PCs that users can upgrade to Windows 8 Pro using the "Windows Upgrade Offer" for people who purchase new machines, or the $39.99 upgrade for owners of existing machines. The limit is meant to stymie businesses that might try to take advantage of the low prices rather than subscribe to expensive volume licensing contracts such as Software Assurance.
6 The version of IE -- as in IE6 -- that Microsoft says isn't supported by the Windows Upgrade Offer website, where customers register for their $14.99 upgrade after buying a new Windows PC.
8 A number both companies' upgrades share.
Windows 8 is, well, the eighth iteration of Windows, according to Microsoft, even though the code version is 6.2, indicating compatibility with the other 6.x editions, Windows Vista (6.0) and Windows 7 (6.1). Likewise, Mountain Lion is the eighth in the line of OS X operating systems, which is why it's numbered 10.8.
14.99 Price, in U.S. currency, of the "Windows Upgrade Offer," the program for customers who buy new Windows 7-equipped machines between June 2, 2012, and Jan. 31, 2013.
19.99 The price, in U.S. dollars, for the OS X Mountain Lion upgrade. That's a 33% reduction from 2011's OS X Lion.
39.99 The price, in U.S. currency, for the discounted Windows 8 Pro upgrade, making it just one-third as much as the list price for an upgrade to 2009's Windows 7 Home Premium.
84.4 The combined share of Snow Leopard and Lion, and thus the percentage of all Macs able to upgrade to OS X Mountain Lion.
92.2 Windows' usage share in June, according to Web metrics firm Net Applications. Of all the personal computers that went online last month, that's the percentage powered by Windows. The closest competitor -- and it's not close at all -- was OS X, with a usage share of just 6.7% worldwide. All other things being equal, Microsoft should outsell Apple on upgrades by almost 14-to-1.
99 The number of days that the $39.99 price for a Windows 8 Pro upgrade will last, assuming Microsoft officially launches its new desktop OS on Oct. 25.
131 Number of markets where Microsoft will sell the Windows 8 Pro upgrade at a discount through January 2013. The company previously published the list -- which starts with Afghanistan and ends with the Virgin Islands -- in this FAQ for the Windows Upgrade Offer.
1-5 million The number of downloaded upgrades that Apple or Microsoft -- perhaps both -- will likely tout in a press release within hours of their deals' debuts.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, send e-mail to firstname.lastname@example.org or subscribe to Gregg's RSS feed .
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