Assembly or ....

[Bob Pendleton]

>From article <1388 at aucs.UUCP>, by 861087p at aucs.UUCP (A N D R E A S):
> 
>      Since this are Newsgroups that mainly programmers write I
> would like to ask them if it really worth it to spend time to
> learn assembly language.I know that when you program in 
> assembly you loose the portability but you gain in speed.
> I've been told also that there are some low-level operations
> that you just can't do in C or any other high level language.
> Apart from this most of the commercial programs are written
> in assembly(Turbo Pascal etc.).Device drivers are also written in assemly.
> So why is everybody against assembly when many programs available are
> written in assembly?
>    I hope I'll get some answers from you guys !!

There are several different questions here. I'll give my opinions on
the ones I think are important. Then I'll sit back and watch the fun.

1) Why should you learn assembly language?

No one should ever learn AN assembly language. You should learn at
least 3 or 4 DIFFERENT assembly lanuages or you are wasting your time.
By different I mean for different machines. Though looking at several
different assemblers for the same machine can be instructive and
amusing.

To really know what a machine will do you need to learn and program in
its assembly language. Learning one assembly language tends to make
you believe that all machines are like the one you know. This can make
you truely blind to the good points of other machines and the horrible
gotchas of your one and only machine. One assmbly language folks can
be real bores at parties and conferences. 

I actually met one idiot who thought that the phrase "assembly
language" was just another name for BAL. He didn't see how I could
possibly be writing in assembly language for an 8080 (dates me, I
know) when he KNEW that BAL didn't generate 8080 machine code. Sigh.

The only way to learn an assembly language is to write in it. Writing
a simple assembler or a simple compiler that emits assembly language
is almost as good.

A complete introduction to the software side of computing should cover
everything from transistors to objects. With some understanding of how
each layer in the hierarchy depends, and is implemented in, the lower
layers. That understanding requires a knowledge of assembly languages
and machine architectures.

Being able to program in assembly languages is also a marketable
skill. What the hey, it's always nice to have a skill to fall back on
:-)

2) Why are some programs written in assembly langauge?

Economics.

Writing in assembly langauge is expensive. But, when the possible
market is large, like say the PClone market. And, speed is important,
which it always is. And processor cycles are a precious resource i.e.
the processor is slow, like on say a 4.77 mhz 8088. And memory is a
precious resource, as it is on every machine in the world, but
especially on PCs. Then the pay back from writing in assembler can be
huge.

That is to say, there is a whole class of marketable applications that
won't fit or will be to slow if you don't write them in assembly. So,
if you want to make a buck, you write it in assembly.

For any given machine, there exists some application that is just
barely doable on that machine. And there exists someone who is
willing, for some reason, to jump through hoops of real fire to make
that application run on that machine.

The cost of high quality compilers for unusual processors is
staggering.  $20,000 to $100,000 and up, is not unusual. There are
cases where you can't afford to write in anything but assembly
language. Of course $100,000 is about one man year of software
engineering time, so this cost might look high up front, but over the
life cycle of a product it might be dirt cheap.

Personal preference.

Some people LIKE to program in assembly language. I like to program in
assembly language, but then I like to write haiku sequences. No
accounting for taste.

I don't like to maintain assembly language. And I hate writing the
same program N times. So I don't write much in assembler.

Expediency.

I've written assembly code because I didn't have a compiler and
couldn't get a compiler. Sometimes the compilers don't exist,
sometimes you can't afford to buy them.

I've written small chunks of assembler to get at instructions the
compiler never generates.

3) Why do people object to using assembly language?

Econonomics.

Assembly code is expensive to write, expensive to maintain, and
nonportable. With modern compilers and modern computers (even PClones)
you can write just about anything in a high level language and get the
size and speed you need. OS dependencies might make it hard to port,
but it can be ported.

You might need a few assembly language routines to access some
hardware or to speed up a few critical parts of the code.  So why pay
the price of writing the whole thing in assembly language?

Esthetics.

Somewhere along the way we all pick up a sense of good and bad, right
and wrong, truth and lie, beauty and ugly... We see something and it
strikes us as good, right, correct, beautiful, it pleases us. A lot of
people see high level code as good, beautiful, and right, and low
level code as bad, ugly, and wrong. Trying to read a piece of assembly
langauge that you wrote last month might convince you that low level
code is indeed bad, ugly, and wrong. Haiku stands the test of time and
readability much better than assembly language.

In summary I'd say that you should learn several assembly languages
because it will give needed insight into machine architectures. And
because when you need to use it, nothing else will do. But, when it
isn't needed, it isn't worth your time, or anyone elses, to use it.

All the questions seemed to assume that the PClone world IS the
computer world. It isn't. Keep that in mind.

			Bob P.

P.S.

Please don't think that any of this is intended as a slam against the
PC world. I just bought one, just because of all the software
available for it. Does anyone know how to get BZONE to work with and
Everex Micro Enhancer II with and EGA monitor? Weird machines, truely
weird ....
-- 
              Bob Pendleton, speaking only for myself.
UUCP Address:  decwrl!esunix!bpendlet or utah-cs!esunix!bpendlet

		Reality is what you make of it.