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Not easily, as they are so very different.
There are different ways to connect and logon. One is CICS, a transaction processor. This is what was used for online systems (banks, airlines etc). A short transaction code is entered followed by the required parameters. For example CANC 1234,231024 might be a cancel transaction on client 1234 for the date 2023-10-24. CICS is configured to invoke a particular COBOL (or other) program for the CANC transaction and pass it the parameters. The program starts up, receives the transaction and parameters from CICS via the equivalent of an API call. It then processes, probably confirming the client number exists, that the date is valid etc, reads the database, and updates the record there. Then when it finishes, it can emit a CICS screen to display or another (probably different) transaction. Thus processing may be chained together, or different programs invoked to guide the user through the processing. But that’s just CICS - more used for a user interface for systems. If you are a developer you probably logon with TSO (Time Sharing Option). This gives you a command line where basic commands may be issued. There are a bunch of built-in system commands but they are mainly for managing datasets. You can write scripts in CLIST (Command LIST) language. These are the equivalent of shell scripts, being able to manipulate datasets and invoke programs. There is also REXX which is a much more sophisticated language. Now as someone else commented, the IBM 327x terminal is not a glorified teletype, because IBM realised way back in the day that it would be much more efficient to only interrupt the computer when something happened, so it doesn’t use constant polling and communication but only interact when the mainframe sends data or the terminal sends an ENTER key (also function keys and some other special ones). This means that when you are typing away you can write a whole screen and the computer doesn’t know about it. When you press ENTER the whole screen is sent and processed and then the response is sent back. There is no live interaction. Which brings me to ISPF. If you are a developer and working on the mainframe (not in an IDE) you will be using ISPF (Interactive System Productivity Facility). This is basically a menu system which makes the computer easier to use than the command line (a proto-gui a bit like the early CPM menu systems?). But ISPF is a lot more than just some menus. It includes an editor (have you ever used a full screen line-oriented editor? It has it’s charms.) and access to the compilers, and functions for allocating datasets, submitting jobs, monitoring jobs etc. Whatsmore, you can write your own ISPF screens and processing. The other wild thing is that screens are defined with fields. Not only for colour, highlighting etc, but for display-only text (no overtyping) or for output or for input. You tab between input fields and enter the required text. This becomes fast and natural which is why those CICS screens in old systems are efficient. It is hard for people used to guis to come to grips with, as you have to understand where you can and can’t type on different screens. |