QUESTION:
I would like to know the kind of computer programming language you are
using to create models, software programs, etc.?
Is FORTRAN still a good computer programming language or is it being
replaced by C and C++?

ANSWER from David Saunders on April 1, 1998:
The bulk of scientific applications such as Navier-Stokes flow solvers and
numerical optimization packages continue to use FORTRAN 77 and (now)
Fortran 90. Graphical applications such as flow vizualization packages and
some grid generation packages tend to use C. I don't think C++ has made
many inroads into the scientific world yet--it tends to be the choice for
modern networking and real-time-type applications.

The main limitations of FORTRAN 77 are its lack of composite data
structures and its inability to allocate memory dynamically, meaning
work-space has to be declared with some maximum size and if a case being
run exceeds those limits then the program has to be recompiled and
relinked with larger limits first.

Fortran 90 does allow dynamic memory allocation and composite data
structures, among other valuable features. Since it is a superset of
FORTRAN 77, it is allowing scientists and numerical analysts to improve
existing software as the needs arise, and write new applications more
conveniently, while still making use of their older software without
significant changes. There is an enormous legacy of existing FORTRAN in
the scientific world, translation of which to some other language (for
whatever reason) is essentially out of the question. Thus some form of
FORTRAN will continue to be used indefinitely, and the current Fortran 90
incarnation is an excellent, powerful language that is still
straightforward to learn and use.

Those with a higher tolerance for cryptic code and "elegance" as
apparently defined to be the fewest symbols performing the most work tend
to like C for some of its powerful features (a variety of pointer types,
operators, and data structures). The object-oriented technology of C++ is
by all accounts even more difficult to master, but evidently pays off by
enabling the proliferation of extremely elaborate software we see in the
PC world today.

It is also possible on most systems to combine software modules written in
different languages. For instance, a modern graphical user interface might
be written in C for an existing scientific package written in FORTRAN,
which would not necessarily have to be translated. Translations can be
hazardous. For example, FORTRAN has always stored matrices by columns
(that is, for elements (i,j) of and m x n matrix A, the elements A(1:m,j)
for a given j are contiguous in memory, and this fact is (or should be)
kept in mind at all times for efficiency reasons. Perversely (?), the
authors of C chose to order the elements the other way (by rows). People
have written software to automate such translations, but the results tend
to be not pretty, and possibly unreliable.

Each language has its place. My bias towards Fortran 90 will be evident,
because I work on numerical applications where it is proving a pleasure to
use. Graphical interfaces have not been required in my work, but there is
no doubt they are becoming generally desirable in this age of information
technology. Learning more than one software language would be wise, as
long as you are able to apply them regularly so as not to forget what you
have learned.

I hope this answers your question. Today's opportunities for competent
software engineers appear more varied and interesting (and challenging)
than ever.

ANSWER from Opal Lemmer on April 1, 1998:
Fortran is a wonderful language for mathematical equations and many 
programs use this language. However, more and more programs that do 
mathematical computations are written in C and often the newer systems 
don't have a Fortran compiler. One reason for this is that C goes  well
with the Unix operating system. Another reason is that  programmers like C
and the Universities use this and it would be hard  to get a new
programmer to come to work in a place where the  programming was done in
Fortran.  

So I think a young person should really concentrate on learning C.   C++
is a little more complicated but is especially useful for graphics 
programs. Also, it allows systems to be changed very easily. Perhaps  you
have heard that maintaining software is more costly than writing  it.
Often a programmer writes some little test program just to use  himself
and people like it so well it becomes widely used. Well, he  probably
wasn't very careful to make it general and changes have to be  made.
Another good example of the problems that arise is the big fuss  over the
year 2000. So anything that makes changes easier is a good  thing. One of
the big wind tunnel systems at Ames Research Center  uses C++. One of the
problems they had was that all of the 
programmers were Fortran programmers and had to learn C++.  

However, just because C and C++ are the big languages now does not  mean
that will be the case a few years from now. You have to be  willing to
learn new things all the time. The important thing to  recognize is how
much is common between the languages. It is quite  easy to learn a new
language if you already know one well. Some old  Fortran programmers who
learn C write C that looks like Fortran.  In  mathematical equations this
could be a good thing because one problem  with C is that it lets
programmers write code that is very hard for  another programmer to read.
I am sorry to say that there are some  programmers who just love to write
that kind of code. Their  supervisors have to watch this very carefully.