On 05/22/2018 05:12 PM, Grant Edwards wrote:
The 3270 was completely screen-oriented. An entire screen was loaded
from the host. That screen included fields with various attributes
(e.g. editable vs. read-only). You could edit whatever was editable on
the screen, and then when you hit "submit" the entire screen was sent to
the host (there may have been an option to send only edited or editable
fields, I don't remember the details). IOW, it worked vaguely like an
HTML page containing a form. Except there were various entertaining
ways things went wrong that don't happen with an HTML form. IIRC, if
you inserted too much data into an improperly defined field, it could
shift everything below it and muck up all the rest of the fields. I also
seem to recall sometimes being able to edit fields that weren't really
supposed to be editable, and then hilarity ensued when you hit submit.
I should have known / remembered that 3270 was screen oriented.
I've made the comparison to HTML forms multiple times myself.
Ya, the editable / non-editable setting was sent by the host and it
trusted that the client would not much with them. A number of mainframe
hackers have leveraged this (mis)feature before.
Some of the fields are similar to hidden fields in HTML forms.
Though I did actually use some genuine IBM green-screen "3270-like"
terminals, most of my experience was with 3270 emulators running under
X11 -- so some of the fun was probably caused by bugs in the emulators.
Yep.
--
Grant. . . .
unix || die
