I started reading it looking for something peculiar to ITS but given the self-contained nature of Emacs it read like a generic Emacs manual, until I got to Appe

I started reading it looking for something peculiar to ITS but given the self-contained nature of Emacs it read like a generic Emacs manual, until I got to Appendix I: > An ideal EMACS keyboard can be recognized because it has a Control key and a Meta key on each side, with another key labeled Top above them. > On an ideal keyboard, to type any character in the 9-bit character set, hold down Control or Meta as appropriate while typing the key for the rest of the character. To type C-M-K, type K while holding down Control and Meta. > You will notice that there is a key labeled "Escape" and a key labeled "Alt". The Altmode character is the one labeled "Alt". "Escape" has other functions entirely; it is handled by ITS and has nothing to do with EMACS. While we are talking about keys handled by ITS, on Meta keyboards the way to interrupt a program is CALL, rather than Control-Z, and entering communicate mode uses the BACK-NEXT key rather Control-_. CALL echoes as ↑Z, but if you type C-Z it is just an ordinary character which happens to be an EMACS command to return to the superior. Similarly, BACK-NEXT echoes as ↑_ but if you type ↑_ it is just an EMACS command which happens not to be defined. > The key labeled "Top" is an extra shift key. It is used to produce the peculiar "SAIL" graphics characters which appear on the same keys as the letters. The "Shift" key gets you upper-case letters, but "Top" gets you the SAIL characters. As EMACS commands, these characters are normally self-inserting, like all printing characters. But once inserted, SAIL characters are really the same as ASCII control characters, and since characters in files are just 7 bits there is no way to tell them apart. EMACS can display them either as ASCII control characters, using an uparrow or caret to indicate them, or it can display them as SAIL characters, whichever you like. The command Control-Alpha (SAIL Character Mode) toggles the choice. Alpha a SAIL character and you can only type it on a terminal with a Top key, but only those terminals can display the SAIL characters anyway. Big gap here because the document only contains the odd-numbered pages as noted in the first page. > including a few that Altmode can't be used for because the correspoding non-Meta character isn't on the keyboard. Thus, while you can't type C -M-; as Altmode Control-;, since there is no Control-; in ASCII, you can type C-M-; as C-C ;. The Control (non-Meta) characters which can't be typed directly require the use of C-^, as in C-^ < to get the effect of C-<. Because C-^ by itself is hard to type, the EMACS command set is arranged so that most of these non-ASCII Control characters are not very important. Usually they have synonyms which are easier to type. In fact, in this manual only the easier-to-type forms are usually mentioned. > In order to type the Help character you must actually type two characters, C-_ and H. C-_ is an escape character for ITS itself, and C-_ followed by H causes ITS to give the Help character as input to EMACS. What a pity that only half the manual is available.