28:  How do I make Emacs display the current line (or column) number?

  To find out what line of the buffer you are on right now, do "M-x
  what-line".  Use "M-x goto-line" to go to a specific line.  To find the
  current column number (as well as some other information), type "C-x ="
  (M-x what-cursor-position).

  If you use these commands often, you might want to bind them to a key.
  See question 113 for instructions on how to do that.

  Typing "C-x l" (or M-x count-lines-page) will also tell you what line you
  are on, provided the buffer isn't separated into "pages" with C-l
  characters.  In that case, it will only tell you what line of the current
  "page" you are on.

  To have Emacs automatically display the current line number of the point
  in the mode line, do "M-x line-number-mode".  You can also put the form

    (setq line-number-mode t)

  in your .emacs file to achieve this whenever you start Emacs.  Note that
  Emacs will not display the line number if the buffer is larger than the
  value of the variable line-number-display-limit.

  The "column" package by Per Abrahamsen <abraham@iesd.auc.dk> permits the
  line and column numbers to be displayed in the mode line; see question 87
  for how to get this package.

  None of the vi emulation modes provide the "set number" capability of vi
  (as far as we know).