[Info-vax] Assembly languages, was: Re: OT: PDP-11 history in arstechnica

[Johnny Billquist]

On 2022-03-18 20:22, Simon Clubley wrote:
> On 2022-03-18, Johnny Billquist <bqt at softjar.se> wrote:
>> On 2022-03-17 01:48, Simon Clubley wrote:
>>> On 2022-03-16, Rich Alderson <news at alderson.users.panix.com> wrote:
>>>>
>>>> ALL the PDP-10 mnemonics for instructions which access memory have the same
>>>> form (taking MOVE as a canonical example):
>>>>
>>>> 	MOVE	load accumulator with contents of memory at effective address
>>>> 	MOVEI	load accumulator with immediate effective address calculation
>>>> 	MOVES	load accumulator with swapped halfwords of contents of memory
>>>> 		at effective address
>>>> 	MOVEM	store accumulator into memory at effective address
>>>>
>>>> Look at the last character of the instruction.  You don't even have to remember
>>>> the difference between "load" and "store".
>>>>
>>>
>>> Doesn't anyone else find it strange that the mnemonic across all
>>> architectures is some variant of MOVE or MOV instead of COPY or CPY ?
>>
>> You mean across all of these two (or three) DEC architectures (PDP-10,
>> PDP-11 and VAX)?
>>
>> Because some others use LOAD, LD, or some variant thereof. And then you
>> have (as mentioned) the PDP-8 which only have TAD (two complement add),
>> so if you want to read something out of memory, you better make sure the
>> AC is 0 before you do. Which of course is helped by the store
>> instruction which implicitly also clears the AC (DCA - Deposit and Clear
>> AC).
>> And there are other things out there as well, if we talk about "all
>> architectures".
>>
> 
> Yes, but that doesn't change my point that with every architecture
> I know (both DEC and non-DEC) that uses a MOV/MOVE mnemonic variant,
> then MOV/MOVE is actually a copy to destination instead as the source
> is not destroyed during the copy.

Ok. Fair enough. You have a point there. I've never considered it 
strange, but I can see that it could be seen that way.

I would think of COPY as being much stranger though, even if it 
semantically would be more appropriate.
You could also consider DEPOSIT, or STORE, or something along those 
lines. But for some reason I prefer MOVE.

   Johnny