Processing data in blocks

From: D. Peschel <dpeschel_at_u.washington.edu>
Date: Thu May 28 00:54:21 1998

> There were also some full-screen editors that relied on the terminal
> to buffer lines of text and let you do your editing in the terminal.
> Those I used tended to run in line block mode (vs. VIEW which I think
> used page block mode) where once the user pressed ENTER the host would
> home the cursor and start sending escape sequences ("<ESC>d" I think,
> followed by a DC1 once the read was pending) to get the terminal to
> send the current line 'til it got to the bottom.
>
> Feel free to ask questions about this if you want to know more.

I hope the invitation isn't directed at only one person. :)

My only experience with block-mode terminals was with a 3278 (or some other
3270 derivative) talking to an AS/400. It was pretty nasty, though that was
partly due to the software on the AS/400 (and the fact that I had no privileges
on the system). All this stuff is made by IBM, in case anyone was wondering.

One thing I realized from the exposure (and have since read about) is that the
local editing features are usually horribly limited, _and_ they're impossible
to extend unless you modify the hardware. What kind of local editing do the
HP terminals provide? (Any fancy cursor movement keys, line editing, cut-
and-paste, etc.?) I'm trying to get a feeling for how well the HP editors
stack up against more modern ones. The line editor sounds pretty nice, actu-
ally. (I use vi -- which is the same kind of full-screen line editor --
a lot. The navigation commands are nice and quick.)

I mentioned reading... there are stories about people trying to combine full-
screen interactive editing with local terminal editing, and finding that the
two don't mix. The people usually bit the bullet, invested in the extra
hardware, and gave the workload back to the CPU. I think there was an enhanced
version of TECO at Stanford that falls into this category. I know that Emacs
on MULTICS was developed like that.

Personally, I found the local editing completely inadequate for dealing with
the multicolumn file lists and pop-up windows the AS/400 kept putting onscreen.
Using only arrow keys to move the cursor to precise places all over the screen
was a real chore. The designs of input and display just didn't match ewll.

-- Derek
Received on Thu May 28 1998 - 00:54:21 BST