Invisible wrote:
> Except that (say) GIF supports animation and only 256 colours and 1-bit 
> alpha, whereas PNG supports only single images, but with 24-bit colour 
> and 8-bit alpha, and TIFF supports something else again...

Um, yes? So? You don't think you can abstract that?  (BTW, GIF supports 
more than that, as you can change the color table after each row. FWIW.)

>> No they're not. Amiga OS devices are things that listen for and 
>> respond to typed messages.  Certainly the narrator isn't a "stream of 
>> octets", nor is the clock, nor is the audio device.
> 
> The narrator accepts a stream of octets. It just interprets them as 
> ASCII text and attempts to synthesize speach for them. But there's 
> nothing stopping you from feeding it with arbitrary binary gibberish.

And the narrator, when read, returns discreet messages with X/Y 
coordinates. Which isn't a stream of octets.

Of course, at some level of detail, everything is a stream of octets. 
It's how the octets are interpreted that's interesting. At some level of 
detail, everything's a voltage too - that's not an interesting level of 
detail for this discussion either. :-)

>>> Oh, well, other than the "minor detail" of compatibility, there's no 
>>> problem at all! ;-)
>>
>> Right. How much C is there that couldn't be ported with relative ease 
>> to C#?
> 
> Um... surely porting C code to *any* other language is intractably 
> difficult?

Uh, no?  Porting C code to C++ is actually fairly easy (almost trivial), 
for example. C# isn't all that different from C, conceptually speaking.

>>> (You recall that "Linux" is actually a tiny bit of software which 
>>> inherited compatibility with Unix, thus earning an instant library of 
>>> userland tools, right?)
>>
>> Sure. Most of which suck. ;-)  Just look at the file system layout you 
>> wound up with.
> 
> What, you mean assigning permissions only to the person that owns the 
> file is a bad idea? You do surprise me. ;-)

No, I mean putting everything that hasn't anything to do with users in a 
directory called "user" is probably a sign of legacy code. :-)

> But my point is... it's much faster than writing an entire OS from 
> scratch, all by yourself. And it instantly gives you a huge library of 
> usable software. Otherwise I suspect Linux would still be nowhere...

Oh, no doubt doing things the same old way makes it easier to port code. 
Not always trivial, mind, but certainly easier. Most operating systems 
that are still around are based on old cruft from 20 years ago for just 
that reason. And obviously Linux didn't do a *sufficiently* good job of 
it, or the amount of UNIX software that people actually want to use and 
is portable is not enough to give Linux significant market share. It's 
really, really difficult to make something that big *actually* 
compatible. (See, for example, all the strangeness in any autoconf.) 
It's probably almost as easy to port most non-GUI Linux utilities to 
Windows as it is to port them to (say) Solaris. The port may be rather 
poor (like, it might not interact with stuff the way you want it to 
under Windows, such as not being startable with "net start" or not 
recording how many unread emails you have for the login screen, say), 
but it'll probably run as well as on Linux without too much hassle.

I'd guess things are way easier to port from UNIX to Windows than from 
either to AmigaOS or Singularity, for example.

I think it's not so much that Linus T said "If I make it look like UNIX, 
I can use all the tools."  I think it was probably at least as much "If 
I make it look like UNIX, I won't have to figure out how an OS *should* 
work."  Hence, it starts out with all the brokenness of UNIX, then 
slowly piles on even more patches to try to make it useful, as long as 
you're not trying to maintain binary compatibility anyway.

-- 
Darren New / San Diego, CA, USA (PST)
  Ever notice how people in a zombie movie never already know how to
  kill zombies? Ask 100 random people in America how to kill someone
  who has reanimated from the dead in a secret viral weapons lab,
  and how many do you think already know you need a head-shot?

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