[R] Newbie graphing questions

[Francisco J. Bido]

Hi everyone.  R is new to me and I'm very impressed with its 
capabilities but still cannot figure out how to do some basic things.  
There seems to be no lack of documentation but finding what I need has 
proven difficult.  Perhaps you can help.

Here's what I'm after:

1.  How do I create a new plot without erasing the prior one i.e., have 
a new window pop up with the new graph? I'm on MacOSX using the Carbon 
port.

2.  How do I pause between plot renderings i.e., in such a way that it 
will draw the subsequent graph after pressing the space bar (or any 
other key).

3.  Illustrating critical regions.  Say I wanted to illustrate the 
critical region of a standard normal.  I would need to draw a vertical 
line from the critical point to the curve and then shade the critical 
region.  How do I do this in R?

Thanks!
-Francisco