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Aucb.835 fa.editor-p utcsrgv!utzoo!decvax!ucbvax!C70:editor-people Sat Apr 3 16:12:36 1982 IBM hardware and screen editors >From cbosgd!mark Sat Apr 3 16:09:43 1982 I've given this problem some thought in the past, although I have never actually used such hardware. I think it is possible to come up with a semi-reasonable screen editor, you just have to accept that you have to type a bit more (a multi letter command with enter at the end).

One major advantage to this approach is that the editor syntax can have the same rules as the command interpreter. For example, on UNIX, you can have editor commands that look like shell commands. This, in theory, makes it easier for a new user to get started since there is only one syntax to learn. Also, you can do the same kinds of things with the commands that you can with the shell: history list, macros, etc. Another advantage is that you can see what you're typing, even get it replayed legibly.

I also believe that IBM terminals have 12 function keys that wake up immediately, allowing you to provide several one-key commands.

My thesis used a line-oriented syntax such as this. I tried to use it and it drove me nuts. I quickly put in a macro capability so that control characters and function keys could be used as one-key commands. This helped a lot. But I am very used to vi, and I can't honestly say how much of my revulsion to the syntax was because I was very used to another editor, and how much was due to the line oriented nature of the input language.

You also have to address input mode vs command mode. The problem is not very different from that in vi/emacs/rand style editors, but at a line level. Either you have a mode, or you prefix either all commands or all text with a "command button". I settled for having a mode, so that the mode determines which type of input requires the command button - this allows a naive user to believe that all commands require the button and there is no notion of modes.

I saw a screen editor at Amdahl for their version of UNIX using IBM terminals. They could edit just as fast with it as I could with vi, although the screen flashed and flickered a lot. It seemed to depend on the 56KB line. I'm not sure, but I think the cursor was always on the command line, making one of the most important screen editor functions (moving the cursor until it is where you want on the screen) virtually useless. I know this was true out of the editor but I can't remember inside - I hope I'm wrong.

Mark

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