Do you remember where you were when this happened?

IBM's entry into the personal computer business on this date in 1981 was a signal event in the history of business and technology. And since then? Oh, a few items of note.

Charles Cooper Former Executive Editor / News
Charles Cooper was an executive editor at CNET News. He has covered technology and business for more than 25 years, working at CBSNews.com, the Associated Press, Computer & Software News, Computer Shopper, PC Week, and ZDNet.
Charles Cooper

Sometimes when you look at the calendar, well, it's better not to look in the first place.

Boy, a lot has changed since then IBM

So it is that today marks an anniversary guaranteed to freak out a good percentage of you who remember this event: Twenty-seven years ago today IBM introduced its first personal computer. Twenty-seven years! Take a deep breath and say thanks for the memories, I guess. (Hey, it's better than the alternative!)

And in the wake of IBM's entry? Oh, a few developments of note:

Apple debuts the Mac
PC clone makers become all the rage
PC mail order
Steve Jobs leaves Apple
IBM, stumbles and is given up for dead
Bill Gates becomes a gajillionaire
Steve Jobs returns to Apple
Bye bye, floppies; hello hard drives
The Internet changes everything
Here comes the iPod
Larry and Sergey go through puberty
Instant messaging
The dotcom boom
The dotcom bust
Mobile phones
Notebook computers
Digital cameras
Computer viruses
Larry and Sergey pass puberty with flying colors
Larry and Sergey become gajillionaires
Social networking
IBM is resurgent
IBM drops out of the PC business
Web 2.0
Cloud computing
Loren Feldman

(This stroll down memory lane, obviously, is not a comprehensive list, so post any of your faves in the Talkback section below. And raise a glass of bubbly while you're at it.)