[TUHS] asm helper routines in v7

[Will Senn]

On 1/4/22 3:12 PM, Dan Cross wrote:
> On Tue, Jan 4, 2022 at 3:38 PM Will Senn<will.senn at gmail.com>  wrote:
>> [snip]
>> My questions are:
>>
>> 1. Is mesg or an equivalent available in v7?
> Perhaps just call printf?
>
>> 2. If not, what was the v7 way of putting strings out?
> Here's what I did:
>
> $ rm -f h h.o
> $ cat h.s
> .globl _printf, _exit
>
> mov     sp, r5
> mov     $hi,(sp)
> jsr     pc,*$_printf
> mov     $0, (sp)
> jsr     pc,*$_exit
>
> hi: <Hello, World!\n\0>
> $ as -o h.o h.s
> $ ld -o h h.o -lc
> $ ./h
> Hello, World!
> $ rm h h.o
>
>> 3. Why aren't the system call names defined?
> If I had to hazard a guess, it would have been to de-emphasize the use
> of assembler for user code, particularly as 7th Edition was starting
> to be portable beyond the PDP-11.
>
>> 4. What was the v7 way of naming system calls?
> I imagine the canonical way to invoke system calls from assembler was
> invoking calling functions in the C library and linking against that.
>
>          - Dan C.
Yep, that worked... you make it look so easy, and your rationales are 
definitely believable :).

Will
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://minnie.tuhs.org/pipermail/tuhs/attachments/20220104/5d8488ed/attachment.htm>