ed-insert (vi input: almost all; emacs: printable characters) In insert mode, insert the input character left of the cursor position. In replace mode, overwrite the character at the cursor and move the cursor to the right by one character position. Accept an argument to do this repeatedly. It is an error if the input character is the NUL character (Ctrl-@). Failure to enlarge the edit buffer also results in an error.
ed-digit (emacs: 0 to 9) If in argument input mode, append the input digit to the argument being read. Otherwise, call ed-insert. It is an error if the input character is not a digit or if the existing argument is already greater than a million.
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self-insert (a, b, A, 1, !, …) Insert yourself.