Re: CICS/400

Hello Mark,

Am 11.08.2023 um 20:48 schrieb Mark Waterbury <mark.s.waterbury@xxxxxxxxxxxxx>:

In CICS "pseudo-conversational" programming, where the program ends after each screen is presented, and when the user fills in the blanks and presses Enter, the next small program (via its own transaction ID) runs to handle that screen, and so on.

Yap, that's how I remember reaving read about it.

That was how you did large applications in CICS back on OS/360 and early OS/VS or DOS/VS, when you had fairly limited region sizes and limited resources (like main storage).

Also a very large pool of terminals being serviced by (seen from our modern viewpoint) a very constrained machine.

S/34 and S/36 had a technique called "SRT" (single requester terminal) and "MRT" (multiple requester terminal) that worked in a similar way. With MRT, one program could handle multiple physical screens (5250s) and handle multiple users, while using far fewer resources, since only one (reentrant) program was loaded into memory.

I see. Is this where the display file INVITE technique comes from?

In CICS, programmers would be "clever" and pass some information in 3270 "non-display" fields, to allow passing data to the next transaction in the sequence. Or CICS had "temp storage" also useful for this kind of thing.

A-ha! Now I know how "3270 cookies" are meant to work. :-D Thanks for that gem!! And your extensive and informative summary!

:wq! PoC