Each buffer remembers previous locations of the mark, in the mark ring. Commands that set the mark also push the old mark onto this ring. One of the uses of the mark ring is to remember spots that you may want to go back to.
Set the mark, pushing it onto the mark ring, without activating it.
Move point to where the mark was, and restore the mark from the ring of former marks.
The command C-SPC C-SPC is handy when you want to
use the mark to remember a position to which you may wish to return.
It pushes the current point onto the mark ring, without activating the
mark (which would cause Emacs to highlight the region). This is
actually two consecutive invocations of C-SPC
set-mark-command); the first C-SPC sets the mark,
and the second C-SPC deactivates it. (When Transient Mark
mode is off, C-SPC C-SPC instead activates Transient
Mark mode temporarily; see Disabled Transient Mark.)
To return to a marked position, use
set-mark-command with a
prefix argument: C-u C-SPC. This moves point to where the
mark was, and deactivates the mark if it was active. Each subsequent
C-u C-SPC jumps to a prior position stored in the mark
ring. The positions you move through in this way are not lost; they
go to the end of the ring.
If you set set-mark-command-repeat-pop to non-
then immediately after you type C-u C-SPC, you can type
C-SPC instead of C-u C-SPC to cycle through
the mark ring. By default, set-mark-command-repeat-pop is
Each buffer has its own mark ring. All editing commands use the current buffer’s mark ring. In particular, C-u C-SPC always stays in the same buffer.
The variable mark-ring-max specifies the maximum number of entries to keep in the mark ring. This defaults to 16 entries. If that many entries exist and another one is pushed, the earliest one in the list is discarded. Repeating C-u C-SPC cycles through the positions currently in the ring.
If you want to move back to the same place over and over, the mark ring may not be convenient enough. If so, you can record the position in a register for later retrieval (see Saving Positions in Registers).