R can not show plots (in Mac OS X terminal)

Dear all:

I am a newbie in Mac. Just installed R and found R did not react on my 
command plot (I use command line in terminal). It did not give me any 
error message, either. All it did was just giving out a new command 
prompt--no reaction to the plot command. I suppose whenever I gives out 
a command of plot, it will invoke the AquaTerm for a small graph, as I 
experience in octave. What can I do for it?

Many thanks,
Minyu Chen