[R] how R outputs?

[xudongyuan]

Hi.All and R developers:
	When I look into the R source code, I have a question.Since R has its own data structure(i.e. SEXP),how does it convert the result to the normal output after it has computed? For example,when I input,
>abs(-3)
I learned that in R's execution, the expression is parsed to a parse tree,and becomes a SEXP list. After "eval" function, the result is still a SEXP. But R outputs:
[1] 3
The output is normal.So my question is how R makes its SEXP result into the normal result.Where can I find the place R makes this convertion in R's source code?Can anyone help me?
		thanks
																dongyuan xu