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"Joe Pluta" <joepluta@xxxxxxxxxxxxxxxxx> wrote:

It's impossible to create a good-looking GUI using the block-mode interface of the 5250. . . . It's your
comparison of an event-driven, keystroke oriented user
interface with the block mode architecture of 5250 that
is flawed at the very lowest level.


Joe, you're better than this. You've got a more than adequate supply of functioning little grey cells between your ears.

Admittedly, as I re-read the paragraph, it's not as bad as it looked the first time, when I thought you'd said that the 5250 data stream itself was "flawed at the very lowest level." But still, saying that block mode is fundamentally incompatible with a GUI is something I'd expect out of somebody who spent his entire career working on asynchronous ASCII terminals (probably in remote-echo mode!) and single-user systems with integrated display and keyboard, where the only way to give users any kind of reasonable response time (even on the simple act of typing!) is with sub-second timeslicing.

The whole point of the 3270 and 5250 data streams (or of using large front-end processors to drive other data streams, instead of forcing the CPU to deal with them directly) is to off-load the business of keeping the user happy onto the terminal and its controller. And indeed, offloading the routine tasks of running a full GUI onto the terminal is not that much more advanced than doing so for a text-based user interface. Indeed, it's quite common: HTML is itself a protocol that offloads everything from keystroke reading to keyboard echoing to mouse gesture management onto the client.

Let's turn this around. For some reason, people have taken to calling 5250-data-stream terminals "dumb," but there's really nothing the least bit dumb about them; they're actually quite sophisticated, as terminals go. Let's talk about terminals that can TRULY be called dumb: so-called "glass teletypes" like the Lear-Siegler ADM-3 (as well as a number of similar units from Teleray). Indeed, for a time, LSI attempted to use "Dumb Terminal" as a quasi-trademark for the ADM-3. All a true dumb terminal does is scrolling 80x24 monochrome text. It doesn't even have cursor addressing: the cursor is captive to the bottom line of the screen. If you had an extensive background in 3270 and/or 5250 (even one limited to the most primitive forms thereof), and the only character-mode asynchronous ASCII terminal you ever laid eyes on was an ADM-3, would you even remotely postulate that a full-GUI X-Terminal, or a full GUI on a single-user system's built-in display, as we know such things today, would be even remotely possible? I daresay you'd laugh in the face of anybody who even suggested it!

An adequate GUI would be possible with 5250 terminals and controllers that exist today; all that's missing are the development tools and documentation. A really good GUI would simply require one or two more generations of terminals, with the 5250 Data Stream evolving with each generation of terminals, at about the rate it was already evolving as we went from 5251s to 3489s.

--
James H. H. Lampert

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