[Simh] RT-11 source

[Dave Wade]

Ray,

 

I really suggest that you look at the Tanenbaum book. It goes into each component of an operating system and explains the structures that it uses and how the parts fit together. Looking at the code often does not explain this. Even were there are comments the usually don’t explain how things mesh, which is all important.

 

Dave

 

From: Simh [mailto:simh-bounces at trailing-edge.com] On Behalf Of Ray Jewhurst
Sent: 23 October 2016 03:20
To: Johnny Billquist <bqt at softjar.se>
Cc: simh at trailing-edge.com
Subject: Re: [Simh] RT-11 source

 

Thank you Johnny. I may ruffle some feathers, but I hate C.  I am mildly autistic and the way my mind works I actually prefer assembly over high level languages. I would really like a blueprint to see what I am doing. Is there commented code for DOS/BATCH? Or even CAPS-11. I would like love to see a fully commented kernel to see what I am up against. 

Thanks 
Ray 

 

On Oct 22, 2016 9:11 PM, "Johnny Billquist" <bqt at softjar.se <mailto:bqt at softjar.se> > wrote:

While we're at it then... Ray asked for RT-11, since he felt that it was smaller and simpler than most other operating systems available, and also because he felt more comfortable with assembler than some other language.

Both those points are missed with any Unix-like OS, even if the intention is good.

I could just as well offer up RSX, since it actually comes with source where the comments are still in place, and it's actually written in assembler for the most part as well. However, it is a much more complex system than RT-11, and in some ways probably more complex than Unix as well. So I don't think it might be a good choice if you just want to understand how an OS works.

In fact, I would probably suggest Ray start with just writing some code to do some simple things without looking at existing code. The first thing needed would be to just have something that can load programs from a device, and run them. This will require some simple device driver, some simple file system, and a simple command line interpreter. Then you can go on an expand from there. You'll soon realize things you want to abstract away, and deal with in a somewhat coherent way.
I wouldn't bother with interrupt system, MMU, or any more fancy stuff to start with. A plain 64K PDP-11, with the program loader just located in one end, and then go from there. Do system calls through TRAP, EMT or some other instruction, and then have a vector installed. If the user program overwrites that, tough luck.

        Johnny



On 2016-10-23 02:45, Nelson H. F. Beebe wrote:

Ray Jewhurst <raywjewhurst at gmail.com <mailto:raywjewhurst at gmail.com> > asks today for documented
operating system source code for the PDP-11.  Besides the Lions' Unix
v6 code, there is also Doug Comer's Xinu project about which he wrote
several books.  Current versions are targeted at x86 and ARM CPUs,

        http://www.xinu.cs.purdue.edu/

but he still provides code for older systems (PDP-11, SPARC, VAX):

        ftp://ftp.cs.purdue.edu/pub/comer/

There is more about him here, including links to his books Web site:

        https://en.wikipedia.org/wiki/Douglas_Comer

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-- 
Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt at softjar.se <mailto:bqt at softjar.se>              ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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