A session playing with the quick and dirty 3174 connected to the 3178 terminal

I made use of my quick and dirty program to write some initial content into the regen buffer for display. It consists of four fields, two protected and one of them intensified. I choose the first console message of MVS 3.8 at IPL time for the first row, protected and intensified, with the rest of that line being a normal intensity unprotected field. 

I picked a common response during IPL as the second line, in a normal protected field, and set the remainder of the buffer to be a normal unprotected field.

My 3174 program should control when I can type into areas and which areas are off limits, as well as showing the desired content on the screen at all time. It is my hypothesis that the terminal itself only interprets the intensity/normal/hidden attribute, but ignores protected or numeric. Here are some screen shots to show the session. 

Data written initially by my program

Initial screen contents

Updating the screen down on line 4 and testing protected and numeric fields

I used the down arrow to advance the cursor one line lower, the typed in some text. This appeared just as I had expected. I then moved up with the arrow keys to the midst of the intensified and protected part of the first line. As I suspected, what I typed overwrote the characters on the screen. Finally, I moved to the middle of the second line, which I had marked as unprotected but numeric. Typed letters wrote right over the field. 

QUICK MOD TO KNOW WHETHER FIELDS ARE PROTECTED AND/OR NUMERIC

I haven't implemented the buffer in my CU yet, I am only writing data to the regen buffer in the terminal. Before I code up the substantial change to manage the buffer and shadow it to regen, I put some quick and dirty functions I can interrogate to ask whether a field is protected and whether it is numeric. I also have a function that gives the cursor position of the next field, allowing me to mimic the TAB key.

As I process keystrokes, but before I write them to the regen buffer, I check for protected fields. If it is protected, I write the status line section that shows the error of attempting entry in a protected field. I pseudo-lock the terminal, meaning I will only accept a RESET key to unblock it. The RESET key erases the error status on line 25.

Testing again

Updated unprotected areas and wrote 05 into numeric field

Status sign indication for protected or alpha-into-numeric field

After pressing RESET to unlock terminal

More numeric input permitted on line 2

I was generally satisfied with this recreation of functionality. I didn't get the TAB support to operate correctly but that wasn't pressing to fix.