Things useful to do for GNU Emacs:

* Primitive for random access insertion of part of a file.

* Making I/O streams for files, so that read and prin1 can
 be used on files directly.  The I/O stream itself would
 serve as a function to read or write one character.

* If a file you can't write is in a directory you can write,
 make sure it works to modify and save this file.

* Make dired's commands handle correctly the case where
 ls has listed several subdirectories' contents.
 It needs to be able to tell which directory each file
 is really in, by searching backward for the line
 which identifies the start of a directory.

* Add more dired commands, such as sorting (use the
 sort utility through call-process-region).

* Make display.c record inverse-video-ness on
 a character by character basis.  Then make non-full-screen-width
 mode lines inverse video, and display the marked location in
 inverse video.

* VMS code to list a file directory.  Make dired work.