special-display-frame-alist

special-display-frame-alist is a variable defined in `window.el'.
Its value is

((height . 14) (width . 80) (unsplittable . t))

• This variable is obsolete since 24.3;
  use `display-buffer-alist' instead.
• This variable may be risky if used as a file-local variable.

Documentation:
Alist of parameters for special frames.
Special frames are used for buffers whose names are listed in
`special-display-buffer-names' and for buffers whose names match
one of the regular expressions in `special-display-regexps'.

This variable can be set in your init file, like this:

(setq special-display-frame-alist '((width . 80) (height . 20)))

These supersede the values given in `default-frame-alist'.

You can customize this variable.