[Discuss] FORTRAN -> ???

[Jerry Natowitz]

As I remember, and I think this is Digital PDP-11 RSX11, you could have disk resident overlays, memory resident overlays, or a mixture of the two. 

Memory resident overlays were a bizarre manifestation of the 16 bit program address spaces  (64K each) coupled with the ability to have at least 22 bits worth of memory ( 4096K).  The base, and all memory resident overlays, were loaded into memory, but the program's address space was limited to the base, one tree of memory resident overlays, and/or one tree of disk overlays.

I can remember spending days on shoe-horning what we thought were huge programs to run in these tiny spaces.  I have a vague recollection that disk overlays were defined using "*" and memory overlays "!".

Now don't get started on core dumps :-)

---- Original message ----
>Date: Tue, 24 Jan 2012 07:42:19 -0500
>From: discuss-bounces+j.natowitz=rcn.com at blu.org (on behalf of Jerry Feldman <gaf at blu.org>)
>Subject: Re: [Discuss] FORTRAN -> ???  
>To: discuss at blu.org
>
>On 01/23/2012 04:55 PM, Jay Kramer wrote:
>>   Excuse me if this is a stupid question given the email chain.  Is it
>> still possible to compile Fortran IV?   Will it run on linux?  I wrote a
>> program in FORTRAN IV that uses overlays but other than that is straight
>> forward code.
>Strange. I have not heard of overlays being used in decades :-)
>BTW: Before we had virtual memory, overlays were used to create a
>smaller memory footprint in a fixed-memory system.
>
>-- 
>Jerry Feldman <gaf at blu.org>
>Boston Linux and Unix
>PGP key id:3BC1EB90 
>PGP Key fingerprint: 49E2 C52A FC5A A31F 8D66  C0AF 7CEA 30FC 3BC1 EB90
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