[kiwidrew]

Did any terminal ever implement the ANSI escape codes for block mode (i.e. form) fields?

The block mode terminals on IBM mainframes (e.g. the 3270) have all the functionality of a basic HTML form if you squint hard enough: the screen is divided into form fields and labels, the user can fill out the fields (and tab the cursor between them) while the terminal is offline/not communicating with the server, and then when the user presses one of the special 'submit' keys the terminal sends all of the data from the form fields to the server and awaits instructions on what to do next.

The 3270 even had hidden fields, so the server could stuff a bit of state information (like a session ID) into the form, which the terminal would dutifully echo back to the server when submitting the form....

It's a very different style of interaction as compared to the conventional Unix/PC character-by-character terminals, and leads to some pretty weird user interface conventions: https://www.youtube.com/watch?v=9qwFSJZSjeA

[jameshart]

Oh that is interesting - I only worked directly with a few terminal systems and never twigged that the 3270s were doing anything fundamentally more sophisticated than WYSE or DEC vt200s. I do remember tabbing between fields on an IBM3090 library catalog search form, though and it being basically an edit and submit process.