SXEmacs can hide lines indented more than a certain number of columns (you specify how many columns). This allows you to get an overview of a part of a program.
To hide lines, type C-x $ (
set-selective-display) with a
numeric argument n. (See Arguments, for information on giving
the argument.) Lines with at least n columns of indentation
disappear from the screen. The only indication of their presence are
three dots (‘…’), which appear at the end of each visible
line that is followed by one or more invisible ones.
The invisible lines are still present in the buffer, and most editing commands see them as usual, so it is very easy to put point in the middle of invisible text. When this happens, the cursor appears at the end of the previous line, after the three dots. If point is at the end of the visible line, before the newline that ends it, the cursor appears before the three dots.
The commands C-n and C-p move across the invisible lines as if they were not there.
To make everything visible again, type C-x $ with no argument.