Controls the way you want the window be split between file-A and file-B (and file-C, if applicable). It defaults to the vertical split (split-window-vertically, but you can set it to split-window-horizontally, if you so wish. Ediff also lets you switch from vertical to horizontal split and back interactively.

Note that if Ediff detects that all the buffers it compares are displayed in separate frames, it assumes that the user wants them to be so displayed and stops splitting windows. Instead, it arranges for each buffer to be displayed in a separate frame. You can switch to the one-frame mode by hiding one of the buffers A/B/C.

You can also swap the windows where buffers are displayed by typing ~.

Controls how windows are split between buffers A and B in the merge mode. This variable is like ediff-split-window-function, but it defaults to split-window-horizontally instead of split-window-vertically.

The value is a function to be called to widen the frame for displaying the Ediff buffers. See the on-line documentation for ediff-make-wide-display-function for details. It is also recommended to look into the source of the default function ediff-make-wide-display.

You can toggle wide/regular display by typing m. In the wide display mode, buffers A, B (and C, when applicable) are displayed in a single frame that is as wide as the entire workstation screen. This is useful when files are compared side-by-side. By default, the display is widened without changing its height.

Controls the way Ediff presents the default directory when it prompts the user for files to compare. If nil, Ediff uses the default directory of the current buffer when it prompts the user for file names. Otherwise, it will use the directories it had previously used for files A, B, or C, respectively.

If t, makes C-h behave like the DEL key, i.e., it will move you back to the previous difference rather than invoking help. This is useful when, in an xterm window or a text-only terminal, the Backspace key is bound to C-h and is positioned more conveniently than the DEL key.

This variable's value is a function that Ediff uses to toggle the read-only property in its buffers.

The default function that Ediff uses simply toggles the read-only property, unless the file is under version control. For a checked-in file under version control, Ediff first tries to check the file out.

If t, all variant buffers are made read-only at Ediff startup.

The default is t, meaning that the buffers being compared or merged will be preserved when Ediff quits. Setting this to nil causes Ediff to offer the user a chance to delete these buffers (if they are not modified). Supplying a prefix argument to the quit command (q) temporarily reverses the meaning of this variable. This is convenient when the user prefers one of the behaviors most of the time, but occasionally needs the other behavior.

However, Ediff temporarily resets this variable to t if it is invoked via one of the "buffer" jobs, such as ediff-buffers. This is because it is all too easy to loose day's work otherwise. Besides, in a "buffer" job, the variant buffers have already been loaded prior to starting Ediff, so Ediff just preserves status quo here.

Using ediff-cleanup-hook, one can make Ediff delete the variants unconditionally (e.g., by making ediff-janitor into one of these hooks).