On The Cruelty of Really Teaching
Computer Science Redux
Owen Astrachan
http://www.cs.duke.edu/~ola
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Shoulders of Giants, Thanks
“… it is a tale
Told by an idiot, full of sound and fury,
Signifying nothing.”
Macbeth, V,v,19
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Where are we going … Questions

What should our concerns be for those choosing to
major in Computer Science?
 courses, research, jobs, …

Should we be concerned by the precipitous decline
in those taking our courses?
 majors, technical students, non-technical …

What can we do to ensure the ongoing success of
our academic discipline?
 Look inward, look to others
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WWDD?
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Questions
If you gotta ask, you’ll never know
Louis Armstrong: “What’s jazz?”
If you gotta ask, you ain’t got it
Fats Waller: “What’s rhythm?”
What questions did you ask in school
today?
Arno Penzias via Isaac Isadore Rabi
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Questions and Answers

Judge a man by his questions rather
than by his answers
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Don’t know much about
history
We are doomed if we don’t pay attention
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Who, when?
“No stretching … is required to envision computer
consoles installed in every home.
Everyone will have better access to the Library of
Congress than the librarian himself now has.
Full reports on current events, whether baseball
scores, the smog index in Los Angles or the minutes
of the 178th Korean Truce Commission will be
available for the asking.”
John, McCarthy, Information, Chapter 1, 1966
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You win some, you lose some
People will soon become discontented with the
“canned” programs available; they will want to
write their own. The ability to write a computer
program will be as widespread as the ability to
drive a car.
Not knowing how to program will be like living in a
house full of servants and not speaking their
language.
Many people can write simple programs after an hour
or two of instruction. … Programming is far easier
to learn than a foreign language or algebra.
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Then and Now
Ouchless I/O
Bailey, SIGCSE 1972
All of the Fortran statements were to be introduced as the need
arose within the context of a problem-solving situation—that
is, a here-is-what-we-want-how-can-we-do-it approach…the
overall objective of the course was to make the instruction as
interesting and informative as possible.
It is remarkable that the majority of students can indeed handle
fairly complex I/O by the end of the first six lessons, even
though they have not actually been formally taught how to do
it.
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Now and Then
Java IO and Testing Made Simple,
Proulx and Rasala, SIGCSE 2004
We believe that the combination of the well-designed tools with
well-designed abstractions presented here provide a solid
foundation for introducing input processing to novice
programmers.
In addition to making the input from the user an integral part
of student's programs, students learn from seeing and using
abstractions that provide tangible and significant benefits.
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1984
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Teaching Compsci in 1984






64K memory, 128K
extended
8-bit, 1 Mhz 6502 processor
5Mb drive: $3500
UCSD Pascal: >$100
Owen's machine: $3000
$677.80 in 1984 has $1200
"purchase power" in 2003

http://eh.net/hmit/ppowerusd/
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Typical machine in 2004?
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



Cruelty of Teaching Computer Science Redux, Fall 2005
1 Gb memory
3+ GHz, 32-bit chip
 Cache, …
160 Gb disk
Lots of free resources
 Good academic
pricing
Under $1000
15
What has changed in 20 years?

Machines
 Characteristics and Availability

Internet
 Availability, IM, web, Google, …

Students
 Comfort with technology, Expectations
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The more things change…?
Assume I took your first
course(s) in 1984 and
understood the concepts
so completely that I could
still get a 100 on the final
from 1984 if I took it today
(e.g., I've been in a
cryogenic chamber). How
would I do on the 2004
final exam?
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What has changed in Physics?
"You'd get a 100 plus or minus sigma. Intro classical
physics hasn't really changed that much over the last
100 years. In graduate level e.g. E&M or quantum
classes I think ditto, although sigma would be bigger
(and might depend more on the instructor variation
than on any real variation in the material). The main
difference is, I think, that your chances of GETTING
100 now would be much higher."
Rob Brown,
Poohbah of Physics Instruction
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What has changed in Biology?
"The basic principles and concepts of biology haven't
changed much in 20 years. What has changed relates
to specific content, and in this arena the changes
have been enormous. 20 years ago, we barely knew
how to sequence DNA; today information of this kind
has had a major impact on just about every topic in
the biological sciences. Thus, some questions on an
exam today would address topics that would be
completely unfamiliar to a 1984 time-traveller. "
Greg Wray,
Director of Undergraduate Studies, Biology
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What has changed in Economics?
"… we now cover material that was only introduced in
an advanced or intermediate course in 1984. In 1984
we spent the bulk of the time dealing with the
Keynesian model and virtually no dialogue about
supply side policies. Now the Keynesian stuff is a
small subset of a much broader exposure to
Aggregate demand and supply… Also there is more
international coverage now - as opposed to 20 years
ago for obvious reasons."
Lori Leachman,
Director of Undergraduate Studies, Economics
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What has changed in Calculus?
We have two varieties of calculus courses, the lab courses and the
traditional ... The latter two have not changed significantly in
decades, and I think that a student who fared well on the 1984
exam in those courses would do well today, and vice versa.
[In the lab courses] You would ace about half the exam. The other
half would be unfamiliar to you. For example, you would
probably not know how to answer a problem on modeling a set
of data, creating an approximation using Euler's method,
interpreting derivatives in the context of applications in other
fields, or giving explanations of ideas …
Lewis Blake,
Supervisor of First-year Instruction
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Changes in Computer Science?
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Changing CS? Rock, Hard place

If Computer Science has changed drastically is it to
keep up with fads and stylistic changes or because
of fundamental changes in the discipline?

Are we leveraging the technological and intellectual
resources at our disposal

If we haven’t changed, is it because of a solid
bedrock of principles that endures? Or because
we’re lazy, good-for-nothing, …
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1985, AP Computer Science, Q2
Write a procedure Compact that eliminates all
elements with value 0 from its argument, a list.
Compact leaves the order of the other elements
unchanged. For example, if list is
(0,9,7,0,0,23,4,0)
When the procedure is called, it should be
(9,7,23,4)
After the procedure executes. All local variables
should be scalar.
(declaration for Pascal record with array and count)
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Concepts and Solutions

Why the restriction to use only scalar
variables?
 Force an expected solution?
 Punish students?
 What is expected solution, O(n) or O(n2)
 What if I make a new array?

What does this look like today? (to appear)
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2004, AP, Question 1
public class WordList
{
ArrayList myList;
public void removeWordsOfLength(int len)
{
// you write this
}
}
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Details of Question Revisited
Write the WordList method removeWordsOfLength.
Method removeWordsOfLength removes all words
from the WordList that are exactly len lettters long
leaving the order of the remaining words unchanged.
For example assume that the instance variable myList of
the WordList animals contains the following:
{“cat”, “mouse”, “frog”, “dog”, “dog”}
After the call animals.removeWordsOfLength(3)
{“mouse”, “frog”}
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What about trends today?
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What is CS? Why study it?
Do we have Physics (Math, …) Envy?
“It's hard for voice over Internet Protocol or
e-commerce to compete with finding the age
of the universe,”
Peter Lee, CMU


Does familiarity breed contempt?
 What was different in 1984 than today?
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Cause for comfort or concern?
Source: CRA
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COHFE
Amherst College, Barnard College, Brown
University, Bryn Mawr College, Carleton College,
Columbia University, Cornell University, Dartmouth
College, Duke University, Georgetown University,
Harvard University, Johns Hopkins University,
Massachusetts Institute of Technology, Mount
Holyoke College, Northwestern University, Oberlin
College, Pomona College, Princeton University, Rice
University, Smith College, Stanford University,
Swarthmore College, Trinity College, University of
Chicago, University of Pennsylvania, University of
Rochester, Washington University in St. Louis,
Wellesley College, Wesleyan University, Williams
College, Yale University
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What’s wrong with this
picture?
Why is the first year different from all other years?
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Algorithm
Arch
OS
AI
CMU
MIT
Stanford
Berkeley
UIUC
Cornell
UTexas
UW
Cal Tech
Wisc
G. Tech
Maryland
Brown
UCLA
Michigan
UNC
Penn
Duke
Harvard
Purdue
CrueltyUCSD
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Books and Approaches Used
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If you don’t take a course in
CS, you won’t major in it.
Why is the first year different from all other years?
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Who's going to College?
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Who's going to College?
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Who's going to College?
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Interdisciplinary minors

At Duke it is difficult to double major in sciences
 Too many requirements, 17 courses in biology

Students are interested in credentials
 No business major/minor, certificate program
(requires intro, capstone, six courses)

Minor requires five courses, double counting ok
 Three courses in CS, two in econ or biology
 From gene to social networks, data mining, …
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Genome Revolution Focus Course

Arts in Contemporay Society, Exploring the Mind,
Evolution and Humankind, 20th Century Europe,
Visions of Freedom, The Genome Revolution and
its Impact on Society, …
 Three of four courses, one writing, two others.
Interdisciplinary 0.5 credit seminar P/F
 Seminars, students live in same dorm
 600+ out of 1600 in FOCUS course

For Genome, 80 applicants for 30 slots, 65% women
 In CS Genomics course 8 women, 9 men
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Simple examples

Given strand of DNA, calculate CG ratio
 Potential source of proteins “CGGATTATC”

Given protein “HLVWW” calculate number of
different DNA strands that could code for it
 64 codons, 20 amino acids

Find heaviest protein in array of proteins
 Given atomic mass of amino acids

Interpret ORF data from NCBI website
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From Algorithms to Objects

Read DNA assumed to be in 5’ to 3’ orientation
 Use BioJava to read via http

Construct reverse complement (3’ to 5’)
 From CAATT produce AATTG

How big is the human genome?
 Runtime of algorithm O(1)
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Computer Science is filled
with real-world examples.
Why is the first year different from all other years?
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A picture is worth …
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A thousand words
Write class Cat that says 'meow'
 Write LoudDog that says 'bark-bark' when Dog
says 'bark'

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How do we teach CS?
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Gries on Teaching Programming
“Suppose you attend a course in cabinet
making. The instructor briefly shows you a
saw, a plane, a hammer, and a few other
tools, letting you use each one for a few
minutes. He next shows you a beautifullyfinished cabinet. Finally, he tells you to
design and build your own cabinet and
bring him the finished product in a few
weeks. You would think he was crazy!”
1974
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Putting it all together …
…we conclude that students are not
given sufficient instruction in how to
"put the pieces together." Focusing
explicitly on specific strategies for
carrying out the coordination and
integration of the goals and plans that
underlie program code may help to
reverse this trend.
Sporher and Soloway,
Novice mistakes: Are the folks wisdoms correct? Studying the
Novice Programmer, 198956
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Changing Data into Knowledge
We provide an unjust education if we do
not give every student the maximum
opportunity for learning. Depending on
their natural abilities, imbalance in
education deprives some students of
learning more than others. Those who are
naturally more creative, or have better
memories, or are more reflective, or are more
active have different opportunities if we do
not provide balance. That is unjust.
James Zull: The Art of Changing the Brain
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Teaching as …
English is not history and
history is not science and
science is not art and art is not
music, and art and music are
minor subjects and English,
history and science major
subjects, and a subject is
something you 'take' and when
you have taken it, you have
'had' it, and if you have 'had' it,
you are immune and need not
take it again." (The Vaccination
Theory of Education?)
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What is CS? Who wants to
study it? Why do they want
to?
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What is Computer Science?
What is the central core of the subject? What
is it that distinguishes it from the separate
subjects with which it is related?
What is the linking thread
which gathers these
disparate branches into a
single discipline? My
answer to these questions
is simple --- it is the art of
programming a computer.
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Is this Computer Science?
public static void stuff(int n){
doit(n,0,1,2);
}
public static void
doit(int n,int f, int t, int a){
if (n == 1) move(n,f,t);
else {
doit(n-1,f,a,t);
move(n,f,t);
doit(n-1,a,t,f);
}
}
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Why Arguments are a Good Thing
Bubblesort,
An Archeological
Algorithm Analysis
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11/08/77
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17 Nov 75
Not needed
Can be tightened
considerably
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Jim Gray (Turing 1998)

Bubble sort is a good
argument for analyzing
algorithm performance. It
is a perfectly correct
algorithm. But it's
performance is among the
worst imaginable. So, it
crisply shows the
difference between correct
algorithms and good
algorithms.
(italics mine)
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Brian Reid (Hopper Award 1982)
Feah. I love bubble
sort, and I grow weary
of people who have
nothing better to do
than to preach about it.
Universities are good
places to keep such
people, so that they
don't scare the general
public.
(continued)
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Brian Reid (Hopper 1982)
I am quite capable of squaring N with or without a
calculator, and I know how long my sorts will
bubble. I can type every form of bubble sort into a
text editor from memory. If I am writing some quick
code and I need a sort quick, as opposed to a quick
sort, I just type in the bubble sort as if it were a
statement. I'm done with it before I could look up
the data type of the third argument to the quicksort
library.
I have a dual-processor 1.2 GHz Powermac and it
sneers at your N squared for most interesting values
of N. And my source code is smaller than yours.
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Niklaus Wirth (Turing award 1984)
I share your view that Bubble Sort has
hardly any merits. I think that it is so
often mentioned, because it illustrates
quite well the principle of sorting by
exchanging.
I think BS is popular, because it fits well
into a systematic development of sorting
algorithms. But it plays no role in actual
applications. Quite in contrast to C, also
without merit (and its derivative Java),
among programming codes.
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Back to the Future
How will we know when we get there?
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A Future for Computer Science?
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What does the Internet look like?
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Is there a Science of Networks?

From Erdos numbers to random graphs to Internet
 From FOAF to Selfish Routing
 Modeling, simulation, and hypotheses
 Computer Science?

From the facebook to tomogravity
 How do we model networks, measure them?
 What mathematics is necessary?
 Will the real-world intrude?
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Network Models (Barabasi)

Differences between Internet, Kazaa, Chord
 Building, modeling, predicting

Static networks, Dynamic networks
 Modeling and simulation

Random and Scale-free
 Implications?

Structure and Evolution
 Modeling via Touchgraph
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My recommendations at Amazon
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And again…
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Finally, …
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From Pigou to Braess

Roughgarden terminology




Selfish Routing
Cost as measure of social
welfare
Non-cooperative agents
Nash flows


Optimality
Game Theoretic
0
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Alan Kay
"Simple things should
be simple. Complex
things should be
possible".
"The best way to
predict the future is to
invent it"
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Who else is similar?
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