To define a region you need to set the mark at one end of it and move the cursor to the other end. Once you set the mark, it remains there until you set it again to some other place. Each buffer has its own mark ring (a place where Emacs remembers 16 previous locations of the mark). To set the mark, you can use the following commands:
This command will set the mark at the position of your cursor
set-mark-command). You can move your cursor around and the
mark will stay there.
Interchange mark and point (
exchange-point-and-mark). Since Emacs
will have only one cursor, after you move the cursor it will be unable
to show you where you set the the mark. In order to see the
mark you can type the command C-x C-x which will put your cursor
on the position of your mark and your mark on the position of your
cursor. Use the command again to reset the positions of your cursor and
This command will push the mark at the beginning of the buffer without changing the position of your cursor.
This command will push the mark at the end of the buffer without changing the position of your cursor.
You can also give arguments to C-< or C->. See The Mark and the Region in SXEmacs User’s Manual, for more information.