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From: pjn@brillig.umd.edu (P. J. Narayanan)
Newsgroups: comp.arch
Subject: Re: It looks like he's at it again!
Message-ID: <PJN.90Jul13074250@brillig.umd.edu>
Date: 13 Jul 90 11:42:50 GMT
References: <1990Jul12.012730.4248@Stardent.COM> <64044@sgi.sgi.com>
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Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
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In-reply-to: karsh@trifolium.esd.sgi.com's message of 13 Jul 90 05:26:27 GMT


	I don't think your criticism of CS practices is completely
fair.  I agree with you that one doesn't have to make religions out of
style that some of the computer scientists may preach. Surely we
shouldn't get bogged down by cosmetics and matters of style (and think
that the number of columns of indentation and the placement of the
comment lines are the most important aspects of CS).

	But, modularity and functional decomposition have their own
merits and should be emphasised even more, in my opinion (of course,
one has to be certain that the definition of modularity doesn't
include the number of columns of indentation as an integral part of
it). However high level a programming language may be, one is still
dealing with primitive concepts when dealing with variables (not to
mention assembly language). Extreme indulgence with such low level
structures is not likely to take you anywhere.  By analogy, have you
ever seen an electrical engineer starting a design off with
transistors and FETs when asked to design an interface for a graphic
device? In hardware design, lot of modularity is enforced by the
necessity to use chips, which correspond to primitive subroutines to
achieve common tasks. Have you also seen any chip manufacturer
marketing a NAND gate chip with some weird pin assignments (and
survived too :-) ? The point is that modularity, whether explicit or
implicit, is essential to complex system design, as one would like to
build on simpler and reliable systems designed earlier. The analogy of
using assembly language when designing a missile tracking program in
VLSI is to start the next 80x86 or 680x0 chip by drawing lines on a
sheet of width lambda and so on.

	That is not to say that we should have any intellectual
blockade against the use of low level structures when efficiency is
important.  If the program market gets as highly competitive as
microprocessor market or TV market, we will start seeing machine or
microcode level optimizations to save milliseconds of running time
(like getting a 24 MHz chip as opposed to a 20 MHz one!). But, just as
a microprocessor designed in such a manner will be (have to be) tested
and well documented (and presented as a package that cannot be
tampered with inside), such efficient programs will have to be tested
and documented well enough to serve as a convenient building block to
other programs.

P J Narayanan