There was a kinda-sorta challenge for me to write the most basic assembler
program to copy a file. Since I am no assembler programmer by any means, it of
course took me some time to get it done. Also I had no clue where to start.
I'd say all total about 5 hours to get it finished. This included reading
docs, books, etc., coding and debugging. And false starts.
You can imagine my immediate frustration when I went off into the EXCP world
(by accident). Then I cheated a little bit and had a peek at George Struble's
_Assembler Language Programming for The IBM System/370 Family_. The 3rd
edition printed 1984, 1st in 1964.
Then I found myself in the QSAM arena, and after that it was quite easy. Here
is my PGM and the two biggest problems I had:
COPYFILE START 0
YREGS
COPYFILE CSECT ,
COPYFILE AMODE 24
COPYFILE RMODE 24
DS 0H
BAKR R14,0 Save caller's ARs and GPRs
LR R12,R15 Set up 1st base register
USING COPYFILE,R12 and inform assembler
OPEN (DCBIN1,(INPUT),DCBOUT1,(OUTPUT))
LOOP DS 0H
GET DCBIN1,INOUTBUF
PUT DCBOUT1,INOUTBUF
B LOOP
EOF DS 0H no more records
CLOSE (DCBIN1,,DCBOUT1)
XR 15,15
PR ,
DCBIN1 DCB BLKSIZE=80,DDNAME=INPUT,RECFM=FB,LRECL=80,DSORG=PS, X
EODAD=EOF,MACRF=GM
DCBOUT1 DCB BLKSIZE=80,DDNAME=OUTPUT,RECFM=FB,LRECL=80,DSORG=PS, X
MACRF=PM
INOUTBUF DS CL80 Input/Output Storage Area
END ,
Notes:
1. That EODAD is nice. As a matter of fact, this looks strangely a lot like a
Cobol program. I can almost see where Grace got her inspiration.
2. Those horrible S0C4's. First one was a S0C4-10, unknown module, and
happened on the OPEN. How could I have debugged this? The problem that I
found from reading (yes reading the docs, I do) the docs carefully, was that
DCB's have to be in 24 bit mode storage. Whoops. Where (and what kind of) in
the dump would show that information?
3. A S0C4-11 because I coded an MVC incorrectly. I coded this:
MVC INOUTBUF(80),=C'Test record'
INOUTBUF DS CL80
A change to MVC INOUTBUF(11),='Test record' works just fine.
I cheated on this one, too. I wasn't able to tell the problem in the
dump. The dump told me it was the MVC instruction that was wrong, so I just
guessed that it was because the MVC wasn't correct.
4. The MACRF options need to be correct, but the assembler warned me about
those. The docs showed all the options, not just QSAM, so I got them mixed up
a little. And I still need to know what MF=T means. The book just says "watch
this one." I guess in 1969, that was enough.
