[Simh] RT-11 source

[khandy21yo]

CP/M works a lot like this. But it's for 8989 not PDP11. It's also been ported to several other systems. Source code is available, but many folks don't consider it an OS.


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-------- Original message --------From: Johnny Billquist <bqt at softjar.se> Date: 10/22/16  7:11 PM  (GMT-07:00) To: simh at trailing-edge.com Subject: Re: [Simh] RT-11 source 
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> 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
>
> -------------------------------------------------------------------------------
> - Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -
> - University of Utah                    FAX: +1 801 581 4148                  -
> - Department of Mathematics, 110 LCB    Internet e-mail: beebe at math.utah.edu  -
> - 155 S 1400 E RM 233                       beebe at acm.org  beebe at computer.org -
> - Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe/ -
> -------------------------------------------------------------------------------
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-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol
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