Keyboard input on IBM mainframes

[jcallen@Encore.COM (Jerry Callen)]

In article <2172@sparko.gwu.edu> mfeldman@seas.gwu.edu () writes:
> [various stuff about the difficulties of doing character I/O
>  on IBM 370 mainframes]
>I conjecture that a sufficiently adept assembler programmer could figure out
>how to end-run the CMS device drivers and then write an interface package
>to make it Ada-callable, but I don't think it would be easy. 

IBM terminal I/O is fundamentally half-duplex. There is possibly a kluge you
could pull on 3270s using "trigger fields" to get data a character at a
time but the overhead would be unspeakable. Unless you are willing to
use somewhat non-standard hardware or hack the OS (ha!) it is just not
possible to do "raw mode" I/O on IBM 370 mainframes. Amdahl's UTS
(Unix for 370s) can do this with special software in the mainframe and
in the terminal controller, but for CMS and TSO it is for all intents
and purposes impossible.

>Given the differences between ASCII and EBCDIC character sets, I find it
>amazing that a decent Ada could have been implemented at all on IBM mainframe
>iron. There are in fact at least two quite decent systems out there, one
>sold by Alsys, the other by IBM, supported, I believe, out of Toronto.

Actually, it's not very hard; you just have to translate everying coming in 
and going out. Bits is bits is bits...

-- Jerry Callen
   jcallen@encore.com

P.S. There's a third "quite decent" Ada for IBM mainframes, from Intermetrics.
	 I don't know if it is actually a product or not. I used to work
	 on it, so I can hardly provide an unbiased assessment. :-)