[fa.works] WORKS Digest V2 #69

works (08/05/82)

>From PLEASANT@RUTGERS Wed Aug  4 19:23:12 1982
Works Digest         Wednesday, 4 August 1982      Volume 2 : Issue 69

Today's Topics:
                        Menu Systems (3 msgs)
                          Display Resolution
             Display Resolution - Plasma Panels (2 msgs)
            Display Resolution - Phototypesetting (2 msgs)


Date: 2 Aug 1982 08:51:22-PDT
From: mo at LBL-UNIX (Mike O'Dell [system])
Subject: Re: WORKS Digest V2 #68

In reply to Sam Hsu's question about menus....

We have used a version of "Menunix"  for training a couple of new
secretaries and have had interesting experiences.  (FYI, Menunix is a
menu-based shell done by Gary Perlman, et al, at ucsd.)  For the first
day or two, the people liked the  menus very much.  However, one of
them actually wandered in and asked "Isn't there some way I can just
type the command I want to do instead of having to do the menus?"  We
think this means the menu interface is nice for rank beginners, but as
soon as they learn what the most frequently-used menus have to say,
they just want to type the command and not be prompted and prodded by
the machine.  On occasion, the people go back to the menu interface
when they want to learn something new, but really seem to be using it
as a help system with the ability to support examples and
experimentation.  They are generally back in their normal shell within
a few minutes.

My personal biases are similar (and may be coloring the
interpretations!).  The menus are nice when you are trying to get a
feel for something very alien, but as soon as you have a "working set"
in your head, you just want to type the commands.  I don't care how
fast you can repaint the menus, and that I can read very quickly; I
simply want to type the commands.



Date: 2 Aug 82 14:12:44-PDT (Mon)
To: works at Rutgers
From: decvax!duke!unc!smb at Ucb-C70
Subject: Re: WORKS Digest V2 #68

The specific failing of menu-based systems is that they force multiple
"mental actions" by the user.  That is, even if the system responds
instantly to present a new menu, I then have to take another step --
which implies thinking about it, and probably a cursor movement (by
whatever technology you want).  A simple typed command, on the other
hand, may be more work, physical and mental -- but it's one thought
sequence, and one action sequence.

                --Steve Bellovin


Date: 3 August 1982 03:19-EDT
From: Robert Elton Maas <REM at MIT-MC>
Subject: Menu systems
To: FHsu at BBNG

It seems to me there are two main uses for a menu a) list of commands
for browsing, i.e. online documentation and b) fast invocation, i.e.
you just press one numbered key or invoke the mouse once, instead of
having to type the spelled-out command name.  The first of these can
be handled by the traditional help-key instead of having an intrusive
(always there even if you don't want it) menu.  In the case of the
second, the ones you use most often are exactly the ones you want in
the intrusive menu, the opposite of what you proposed.

    Date: 28 July 1982  10:00-EDT (Wednesday)
    From: Sam Hsu <FHsu at BBNG>

    Suppose the menu system kept track of command usage, and displayed
    only a subset of commands, say, the useful ones but not yet used a
    lot (assuming the often used ones were already mastered), or the
    appropriate ones in a certain context.

The ones you use all the time are the ones you want in the menu,
immediately available always, with minimal keystrokes/mousestrokes.
The useful ones you haven't used recently are the ones you want in the
optional help you get only when you ask for them.  <My opinion of


Date:  1-Aug-82 18:54:57 PDT (Sunday)
From: Hamilton.es at PARC-MAXC
Subject: Re: Display resolution
To: Jeff La Coss  <JLACOSS at USC-ISIB>, Fischer at RUTGERS

        "The trouble with all of this is that the video bandwidth
        required to do any of this is cosmic. No problem generating it
        (well, maybe no problem) but displaying it is quite another
        matter. Building a monitor that can swing the beam fast enough
        to do 1000 lines/frame is a trick only a few vendors have
        managed. 300 lines/inch resolution will require 3000
        lines/frame. Ouch. In addition, the beam is going to have to
        be modulated at about 250 MHz. The only way to do this will be
        to up voltages/currents in the amp circuit and increase the
        anode voltage- don't sit in front of this tube if you ever
        want to procreate."

One answer seems to me to have multiple guns on one tube.  Why not
divide the screen into nine squares and drive one high-res gun for
each?  I realize adjusting all the edge convergences could be a slight
problem, but I don't see why it shouldn't be within the state of the



Date:  2 Aug 1982 1445-EDT
Subject: Re: Display resolution
To: Hamilton.es at PARC-MAXC, JLACOSS at USC-ISIB

Another way to build really high resolution displays is to keep from
using a technology that requires refreshing the screen.

One way might be with plasma panels, which are effectively their own
memory.  Each dot on the display is similar to a neon bulb, with an
anode and a cathode and neon gas in the gap between.  Dots are turned
on with a short higher voltage pulse and then continue to glow because
of a constant background voltage.  The initial pulse ionizes the neon
in the gap, which then stays lit using the lower "maintaining"

I assume the problem with building a high resolution display with a
plasma panel would be that as the cell size goes down it gets dimmer.
I wonder what the practical limits are for the narrowness of the gap
between the cathode/anode in a plasma panel and or the closest spacing
between cells?  (do existing panels isolate the display cells with
walls of a dielectric?)  Or we might be limited by the amount of
energy to be dissipated in each cell (the glow of the glass panel
cannot be brighter than the cells in it...)

Or how about other technologies; liquid crystal and electroluminescent
to name two?  The Grid/Compass portable computer (or workstation if
you prefer) has an electroluminescent display of low resolution.



Date: 3 Aug 82 13:28:12-PDT (Tue)
From: decvax!pur-ee!uiucdcs!grunwald at Ucb-C70
Subject: Re: Display resolution - (nf)

Having use plasma panels for 6 years (PLATO rears its ugly head), I'll
toss in what little I know about it:

The main problem with plasma panels is dot density, since when you
increase the density of the dots too much, you get "accidental"
firings of some dots. This also happens when the panels get older. At
last report, the Army had a three foot by three foot panel constructed
for high-altitude / high-resolution applications. I don't know how
many pixels wide and high it was, but I imagine it was either
1024x1024 or 2048x2048.

Additionally, several Japanese companies (Nippon Bell is one, I think)
are getting into the plasma panel market. They are trying to get color
plasma panels to work, as well as develop other fast panels. The
color panels work by putting phosphores where the dots light up and
using that energy to excite the phosphore (or so they said). The
"fast" panels they were working on at the time they came and talked to
us were called "shift panels" -- they were slightly different in
design from the standard panel. They create an image at the far right
on a 16 pixel tall space and then "shift" it over to where it should
be. This causes some really strange effects and seems to only be very
useful for alphanumerics or customized character sets.  Their main
advantage is that they are much flatter than normal plasma panels and
it would be practical to make a plasma based TV.


Date:  2 Aug 1982 0946-EDT
From: G.Tech at MIT-EECS at MIT-AI (The Tech)
Subject: Display Resolution

Sorry this is late (coming after the summary), but seeing all the
references to "book quality" made me want to add my 2 cents:

In the phototypesetting business, very few people will accept less
than 1000 lines/inch for their originals.  Two typesetters, the
Alphatype CRS and the Compugraphic 8600, generate 5000 lpi.  It's
possible to generate 1000+ newspaper lines/minute at 1000lpi using a
text window of 1 inch for $70,000.  (The photographic paper moves past
the window.)

Someone with better contacts in the industry may be able to provide
more info, but I'd say "book quality" is a long way off for



Date: 3 Aug 82 19:34:00-PDT (Tue)
From: decvax!utzoo!henry at Ucb-C70
Subject: more on display resolution

Actually, display terminals are a *worse* problem than
phototypesetters.  People doing phototypesetting have one big
advantage:  almost all their stuff is intended to be reproduced by
printing processes, which cannot reproduce 1000 lines/inch.  (In fact,
it's a bit peculiar that people bother investing in 5000 lines/inch
phototypesetters when all that extra resolution is totally wasted on
the final product.)  Trouble is, the human eye can see 1000 lines/inch
jaggies.  If you want a screen that looks like a printed page, yea
unto the very limits of the human eyeball, you are going to need *even
higher* resolution.

On the other hand, if you are a reasonable man rather than one of the
graphic-arts types who buys a 5000 lines/inch phototypesetter because
when he looks at the original (*not* the mass-production product) with
a magnifying glass he can see the dots in 1000 lines/inch output, then
you may be able to content yourself with much lower resolution.  I
have heard that the critical resolution for "smooth looking" output is
somewhat dependent on the dynamic range of light intensities, and CRTs
actually are somewhat better off than paper (i.e. need less resolution
to look good).

There was a *very* interesting paper in Siggraph a year or two ago.
The author (alas, I don't remember his name, and my Siggraphs aren't
handy) claimed that standard NTSC resolution actually approaches the
limits of the human eye, if used *right*.  You need a good monitor,
plus possibly some hardware fiddling so the scan lines touch each
other (normally there is black space between them).  You need *at
least* 8 bits of gray scale, and your software must *USE* it properly.
Oh yes, and your D-A conversion must be calibrated properly so that
that 8-bit range really does turn into the right sort of range of
light intensity.  The explanation of why this works relies on things
like halftoning effects, and I can't reproduce all of it off the top
of my head;  the key fact is that the resolution of the human eye is
not a single number, but a complex phenomenon, and by doing things
right you can do an end-run around resolution limits.  Don't flame to
me that it's impossible, read the article first.  It's in one of the
Siggraph conference proceedings, probably two years ago, titled
something like "The 8000-line display".

						Henry Spencer


End of WorkS Digest