I bought a Macmini, and the first thing I had to inquire...

I bought a Macmini (Snow Leopard 10.6.4). It's the first Mac OS machine to me. So there are some different UXs with Linux or Windows. The first goal to me is to use ruby 1.9 on my Mac. But the first thing I had to inquire is ... to take a screen shot! It's the most different thing with Linux or Windows. I found this approach by google. I re-summarize 3 screenshot tips below:

• [Command]+[Shift]+[3] takes a screenshot of entire desktop, and save the PNG file to desktop.
  
  
  
  If you press [control] at same time, output goes to clipbord(doesn't go to desktop).
• [Command]+[Shift]+[4] takes a screenshot of rectangular portion with dragging crosshair cursor, and save the PNG file to desktop.
  
  
  
  If you press [control] at same time, output goes to clipbord(doesn't go to desktop).
• {[Command]+[Shift]+[4] and spacebar} takes a screenshot of specific window with highlighting camera cursor, and save the PNG file to desktop.
  
  
  If you press [control] at same time, output goes to clipbord(doesn't go to desktop).

Well, I can finally begin to operate installing Ruby 1.9.