[J3] Questions about dusty CDC 3400 deck

[Dick Hendrickson]

On Sun, Mar 24, 2024 at 3:31 PM Van Snyder via J3 <j3 at mailman.j3-fortran.org>
wrote:

> I'm trying to resurrect a CDC 3400 program.
>
> It has weird stuff that is easy to repair, such as numeric common block
> identifiers
>

Be careful with numeric common blocks. There was something odd about them.
Possibly the way they interacted with the OVERLAY loader or maybe where
they were placed in memory. Might have been harmless as they were placed in
high memory so they "recovered “ the storage used be the linker/loader and
,thus, couldn’t be DATA initialized. Remember the CDC family didn’t have
virtual memory and 32 thousand words was “big iron”

the same labels for FORMAT and executable statements, references to
> vendor-specific intrinsics such as TIMELEFT and SKIPFILE. and weird but
> obvious IF statements such as IF(EOF,60) 1,2. There is a manual online, but
> there's stuff it doesn't expalin.
>
> The program changes a DO index. Does anybody remember whether that changes
> the looping, or is that established when the DO statement is executed?
>

I’m sure it changed the looping count. At least it would on  immediate
predecessor the 1604. IIRC, the “iteration count “ was a FORTRAN 77
invention.

>
> It references a 2D array using one subscript (albeit only in a PRINT
> statement). Does anybody remember which element that would access? Would it
> be the one in array-element order?
>

Yes definitely tha array element order. A common extension when optimizers
couldn’t optimize nested loops and memory was scarce

Dick Hendrickson


> Thanks,
> Van
>
>
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