Linux vs Windows: What do programmers use.

I was woundering if it is a common theme for most "Pro" programmers to use linux. I mean a book called C;Programming I have was written on linux. So which OS is it that programmers or hackers, per say, use?

We professional programmers use whatever we're paid to use.  In my case, Microsoft products.

At home, I use multiple OSes.  Windows and Linux right now, and I'm saving up for another machine that I hope to put Solaris 10 on.  :)