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From: "Alf P. Steinbach" <alfps@online.no>
Subject: Re: What's the best language to start with? [was: Re: Should I learn
 C or Pascal?]
Date: 1996/08/06
Message-ID: <3206BAE5.4CB4@online.no>#1/1
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 <dewar.838609515@schonberg>
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Date: 1996-08-06T00:00:00+00:00
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Robert I. Eachus wrote:
>    There are still CPU chips being manufactured which implement the
> semantics of something close to assembler in a direct manner.  But I
> doubt any are used in new designs...  In most modern CPU chips the
> relation between the abstract machine API and the execution state of
> the chip is tenuous at best.  So the distinction between C and
> assembler is a distinction without a difference.  They both provide
> incompletely specified virtual machines which programs can be written
> against.  (And no, the hardware is NOT a specification for the
> assembler.  Things left unspecified by the API are different in
> different SPARC chipsets for example.)

Either you're saying something I don't get, or you're not saying
anything at all.  There are at least three issues on the table:
(1) the header of the thread, now long forgotten;  (2) whether
students / beginning programmers are best off learning from the
bottom up, starting with the v.N. architecture, or from the top
down, starting with some suitably high-level language, or using
a gradient blending of the two (my view);  (3) a clarification of
what's meant by "abstract" and "concrete" in the context of
programming  --  which seems to be the issue of your posting.

Re issue (3), there are levels upon levels upon levels:  my point
here is that when you look from level n, "concrete" refers to
levels n-1, n-2 and so on (toward the physical world), whereas 
"abstract" refers to level n, n+1 and so on, of which there are
an infinity you can make up just as you want, and an infinity of
possible levels n+1 coexisting.  Of course these terms are relative.
Everything is relative to something.  For me, that's a truism.

The argument against disregarding or hiding the concrete (levels n-1,
n-2 etc. when you are learning about level n) is simply that the 
particular instance of a level n you're learning about was abstracted 
from the concrete levels, and your understanding of level n will be 
lacking if you don't know anything about the concrete, the *why*s of
the solutions and abstractions at level n.  It's like saying "Do things 
this way, follow the cookbook recipes, but for God's sake don't try to 
understand it:  that will lead you into temptation and severe trouble".
Likewise, disregarding higher level abstractions is just as silly.
In many cases, solutions at a level n are guided by higher level
abstractions  --  the "ideal"  --  and fit as best possible to n-1.

- Alf