[Coco] Drive Wire strangeness

[Gene Heskett]

On Monday 09 December 2013 01:03:35 Robert Gault did opine:

> Steve Ostrom wrote:
>  ><snip>
>  >
> > It seems as if OS-9 is not very intuitive, which might mean it is very
> > strong.  If I put a similar effort into learning OS-9 from manuals and
> > other sources as I have in learning BASIC and 6809 assembly, will I
> > be able to write OS-9 programs just as easily?  I know this is really
> > late in the game for Coco programming, but I've recently retired, and
> > now have more time to spend on the Coco.  I'd love to create some
> > kind of OS-9 program, even if it is not very useful, and it would be
> > for my use only.
> > 
> > Programs that are written in OS-9 for the Coco, could they have been
> > written easier in assembly or BASIC?  Were they written in OS-9 for
> > portability only, or because the programmer could do things in OS-9
> > that they could not in assembly or BASIC?  I realize that BASIC is
> > slow, and is an interpreted language. Assembly is native and
> > blazingly fast.  What are the advantages in writing software in OS-9,
> > besides portability to other systems that also run OS-9?
> > 
> > Thanks for your opinions.
> 
> Steve,
> 
> Well you certainly are correct in saying if a program can be written in
> pure assembly, it will be at least as good if not better and faster
> than one in OS-9 assembly. That being said there are reasons for using
> a higher level language than machine language.
> 
> OS-9 at the command level is a portable language as it should work on
> any OS-9 computer. But you are, I think, trying to compare pure
> assembly to OS-9 assembly language. There is not much difference except
> that OS-9 system calls act as a bridge to the hardware.
> 
> For example with OS-9 assembly, it is easier to write programs that need
> disk I/O or screen I/O as that is handled by system calls. You don't
> need to reinvent the wheel for each program you want to write.
> There are few really good entry points to the Basic and Disk ROMs so the
> number of simple "system calls" are very limited compared to what is
> available in OS-9.
> 
> Now if writing with OS-9 commands is too complicated, just move to a
> still higher level language, Basic09, to get a language more powerful
> and just as easy to use as Disk Basic.
> 
> Robert
> 
> 
The main advantage to writing assembly in os9 was that with virtually zero 
effort, your code was truly position independent, it could run anyplace in 
memory that os9 could load it into.  ALL branches and conditional jumps are 
100% relative to the current value of the program counter after it has 
executed that command.  Housekeeping wise, that is a huge relief.

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Cheers, Gene
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