[Simh] Fwd: Assembler programming under Unix - was VAX/VMS

[Kevin Handy]

Any more, with the optimizing compilers we have today, it doesn't make much
sense to use machine language for most program development.
1. The compilers often produce better code that the average programmer
would produce, and often better than a good one would produce. The
optimizer doesn't care about making readable code, so it can do aggressive
things to the code that a human wouldn't wnt to. LLVM is even working with
optimizations across compilation units.
2. Portability issues. If you write in machine language on a VAX/VMS, that
is all it will run on. Porting it to VAX/Unix
 might be possible, put with the differing system interfaces, not easy.
3. Ease of development. Developing in a higher level language is usually
faster than in a machine language environment. It is also often easier for
others to quickly comprehend. One line in high level code, "a=b*c+d*e",
verses numerous lines of assembly code.
4. What do you do if your platform suddenly gets new opcodes. This happened
with the Alpha, Intel x86, and many others. Update your code, or leave it
the same so it can still run on older hardware?

There are some places where hand-coded machine code is useful, but its use
isn't as necessary as it used to be. It can be interesting to know some of
the details.


On Mon, Feb 15, 2016 at 1:47 PM, Mark Wickens <mark at wickensonline.co.uk>
wrote:

>
>
>
> -------- Forwarded Message --------
> Subject: [Simh] Assembler programming under Unix - was VAX/VMS
> Date: Mon, 15 Feb 2016 20:46:46 +0000
> From: Mark Wickens <mark at wickensonline.co.uk> <mark at wickensonline.co.uk>
> To: Clem Cole <clemc at ccc.com> <clemc at ccc.com>
>
> On a related note,
>
> Programming in assembly language for modern Unix always seemed a bit
> haphazard to me and the assemblers a bit non-standard and poorly
> documented, but maybe I have a skewed view.
>
> Does programming the VAX under Unix fair any better in terms of assembler
> quality and documentation?
> I appreciate that assembler programming for Unix may be frowned upon given
> the C heritage.
>
> Feel free to tell me I'm wrong... about anything!
>
> Regards, Mark.
>
> On 15/02/16 17:21, Clem Cole wrote:
>
> below...
>
> On Mon, Feb 15, 2016 at 12:14 PM, Will Senn <will.senn at gmail.com> wrote:
>
>> What is a good source to learn a bit about VAX/VMS and the relationship
>> of the VAX and PDP-11 architectures and programming differences?
>
>
> ​ Hmm probably this list....😈​
>
>
>
>
>
>
>> I looked at the Wikipedia article. I'm not sure it is entirely accurate
>> and it is sketchy on particulars.
>>
> Which one - the VAX/VMS article?
>
>
>
>
>>
>> Also, can the Vax run v6 or v7?
>>
> ​32V is the original V7 to the 780.​
>
> Nothing there much that you will learn that you can not learn from V7 on
> the 11/70.  It does have a newer compiler.
>
> If you want to see UNIX on an 780, start with BSD 4.1
>
>
>
>
>>
>> Thanks,
>>
>> Will
>>
>
>
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