(Parts of this essay began as replies to students who wrote to
me with questions.)
Recently I've had several emails from computer science
undergrads asking what to do in college. I might not
be the best source of advice, because I was a philosophy major in
college. But I took so many CS classes that most CS majors thought
I was one. I was certainly a hacker, at least.
What should you do in college to become a
good hacker? There are two
main things you can do: become very good at programming, and learn
a lot about specific, cool problems. These turn out to be equivalent,
because each drives you to do the other.
The way to be good at programming is to work (a) a lot (b) on hard
problems. And the way to make yourself work on hard problems is
to work on some very engaging project.
Odds are this project won't be a class assignment. My friend Robert
learned a lot by writing network software when he was an
undergrad. One of his projects was to connect Harvard to the
Arpanet; it had been one of the original nodes, but by 1984 the
connection had died.  Not only was this
work not for a class, but because he spent all his time on it
and neglected his studies, he was kicked out of
school for a year.  It all evened out in the end, and now he's
a professor at MIT. But you'll probably be happier if you don't
go to that extreme; it caused him a lot of worry at the time.
Another way to be good at programming is to find other people who
are good at it, and learn what they know. Programmers tend to sort
themselves into tribes according to the type of work they do and
the tools they use, and some tribes are
smarter than others. Look
around you and see what the smart people seem to be working on;
there's usually a reason.
Some of the smartest people around you are professors. So one way
to find interesting work is to volunteer as a research assistant.
Professors are especially interested in people who can solve tedious
system-administration type problems for them, so that is a way to
get a foot in the door. What they fear are
flakes and resume padders. It's all too
common for an assistant to result in a net increase in work. So
you have to make it clear you'll mean a net decrease.
Don't be put off if they say no. Rejection is almost always less
personal than the rejectee imagines. Just move on to the next.
(This applies to dating too.)
Beware, because although most professors are smart, not all of them
work on interesting stuff. Professors have to publish novel results
to advance their careers, but there is more competition in more
interesting areas of research. So what less ambitious professors
do is turn out a series of papers whose conclusions are novel because
no one else cares about them. You're better off avoiding these.
I never worked as a research assistant, so I feel a bit dishonest
recommending that route. I learned to program by writing stuff of
my own, particularly by trying to reverse-engineer Winograd's
SHRDLU. I was as obsessed with that program as a mother with a new baby.
Whatever the disadvantages of working by yourself, the advantage
is that the project is all your own. You never have to compromise
or ask anyone's permission, and if you have a new idea you can just
sit down and start implementing it.
In your own projects you don't have to worry about novelty (as
professors do) or profitability (as businesses do). All that matters
is how hard the project is technically, and that has no correlation
to the nature of the application. "Serious" applications like
databases are often trivial and dull technically (if you ever suffer
from insomnia, try reading the technical literature about databases)
while "frivolous" applications like games are often very sophisticated.
I'm sure there are game companies out there working on products
with more intellectual content than the research at the
bottom nine tenths of university CS departments.
If I were in college now I'd probably work on
graphics: a network game, for example, or a tool for 3D animation.
When I was an undergrad there weren't enough cycles around to make
graphics interesting, but it's hard to imagine anything more fun
to work on now.
When I was in college, a lot of the professors believed (or at least
computer science was a branch of math. This idea was
strongest at Harvard, where there wasn't even a CS major till the
1980s; till then one had to major in applied math. But it was
nearly as bad at Cornell. When I told the fearsome Professor Conway
that I was interested in AI (a hot topic then), he told me I should
major in math. I'm still not sure whether he thought AI required
math, or whether he thought AI was nonsense and that majoring in
something rigorous would cure me of such stupid ambitions.
In fact, the amount of math you need as a hacker is a lot less
than most university departments like to admit. I don't think you
need much more than high school math plus a few concepts from the
theory of computation. (You have to know what an n^2 algorithm is
if you want to avoid writing them.) Unless you're planning to write
math applications, of course. Robotics, for example, is all math.
But while you don't literally need math for most kinds of hacking,
in the sense of knowing 1001 tricks for differentiating formulas,
math is very much worth studying for its own sake. It's a
valuable source of metaphors for almost any kind of work. I wish
I'd studied more math in college for that reason.
Like a lot of people, I was mathematically abused as a child. I
learned to think of math as a collection of formulas that were
neither beautiful nor had any relation to my life (despite attempts
to translate them into "word problems"), but had to be memorized
in order to do well on tests.
One of the most valuable things you could do in college would be
to learn what math is really about. This may not be easy, because
a lot of good mathematicians are bad teachers. And while there are
many popular books on math, few seem good. The best I can think
of are W. W. Sawyer's. And of course Euclid. 
Thomas Huxley said "Try to learn something about everything and
everything about something." Most universities aim at this
But what's everything? To me it means, all that people
learn in the course of working honestly on hard problems. All such
work tends to be related, in that ideas and techniques from one
field can often be transplanted successfully to others. Even others
that seem quite distant. For example, I write
essays the same way
I write software: I sit down and blow out a lame version 1 as fast
as I can type, then spend several weeks rewriting it.
Working on hard problems is not, by itself, enough. Medieval
alchemists were working on a hard problem, but their approach was
so bogus that there was little
to learn from studying it, except possibly about people's ability
to delude themselves. Unfortunately the sort of AI I was trying
to learn in college had the same flaw: a very hard problem, blithely
approached with hopelessly inadequate techniques. Bold? Closer
The social sciences are also fairly bogus, because they're so much
influenced by intellectual fashions. If a
physicist met a colleague
from 100 years ago, he could teach him some new things; if a psychologist
met a colleague from 100 years ago, they'd just get into an
Yes, of course, you'll learn something by taking a
psychology class. The point is, you'll learn more by taking
a class in another department.
The worthwhile departments, in my opinion, are math, the hard
sciences, engineering, history (especially economic and social
history, and the history of science), architecture, and the classics.
A survey course in art history may be worthwhile. Modern literature
is important, but the way to learn about it is just to read. I
don't know enough about music to say.
You can skip the social sciences, philosophy, and the various
departments created recently in response to political pressures.
Many of these fields talk about important problems, certainly. But
the way they talk about them is useless. For example, philosophy
talks, among other things, about our obligations to one another;
but you can learn more about this from a wise grandmother or E. B.
White than from an academic philosopher.
I speak here from experience. I should probably have been offended
when people laughed at Clinton for saying "It depends on what the
meaning of the word 'is' is." I took about five classes in college
on what the meaning of "is" is.
Another way to figure out which fields are worth studying is to
create the dropout graph. For example, I know many people
who switched from math to computer science because they found math
too hard, and no one who did the opposite. People don't do hard
things gratuitously; no one will work on a harder problem unless
it is proportionately (or at least log(n)) more rewarding. So
probably math is more worth studying than computer science. By
similar comparisons you can make a graph of all the departments in
a university. At the bottom you'll find the subjects with least
If you use this method, you'll get roughly the same answer I just
Language courses are an anomaly. I think they're better considered
as extracurricular activities, like pottery classes. They'd be far
more useful when combined with some time living in a country where
the language is spoken. On a whim I studied Arabic as a freshman.
It was a lot of work, and the only lasting benefits were a weird
ability to identify semitic roots and some insights into how people
Studio art and creative writing courses are wildcards. Usually
you don't get taught much: you just work (or don't work) on whatever
you want, and then sit around offering "crits" of one another's
creations under the vague supervision of the teacher. But writing and
art are both very hard problems that (some) people work honestly
at, so they're worth doing, especially if you can find a good
Of course college students have to think about more than just
learning. There are also two practical problems to consider: jobs,
and graduate school.
In theory a liberal education is not supposed to supply job training.
But everyone knows this is a bit of a fib. Hackers at every college
learn practical skills, and not by accident.
What you should learn to get a job depends on the kind you want.
If you want to work in a big company, learn how to hack
Windows. If you want to work at a cool little company or research
lab, you'll do better to learn Ruby on Linux. And if you want to
start your own company, which I think will be more and more common,
master the most powerful tools you can find, because you're going
to be in a race against your competitors, and they'll be your horse.
There is not a direct correlation between the skills you should
learn in college and those you'll use in a job. You should aim
slightly high in college.
In workouts a football player may bench press 300 pounds, even
though he may never have to exert anything like that much force in
the course of a game. Likewise, if your professors try to make you
learn stuff that's more advanced than you'll need in a job, it may
not just be because they're academics, detached from the real world.
They may be trying to make you lift weights with your brain.
The programs you write in classes differ in three critical ways
from the ones you'll write in the real world: they're small; you
get to start from scratch; and the problem is usually artificial
and predetermined. In the real world, programs are bigger, tend
to involve existing code, and often require you to figure out what
the problem is before you can solve it.
You don't have to wait to leave (or even enter) college to learn
these skills. If you want to learn how to deal with existing code,
for example, you can contribute to open-source projects. The sort
of employer you want to work for will be as impressed by that as
good grades on class assignments.
In existing open-source projects you don't get much practice at
the third skill, deciding what problems to solve. But there's
nothing to stop you starting new projects of your own. And good
employers will be even more impressed
What sort of problem should you try to solve? One way to answer
that is to ask what you need as a user. For example, I stumbled
on a good algorithm for spam filtering because I wanted to stop
getting spam. Now what I wish I had was a mail reader that somehow
prevented my inbox from filling up. I tend to use my inbox as a
todo list. But that's like using a screwdriver to open
bottles; what one really wants is a bottle opener.
What about grad school? Should you go? And how do you get into a
In principle, grad school is professional training in research, and
you shouldn't go unless you want to do research as a career. And
yet half the people who get PhDs in CS don't go into research.
I didn't go to grad school to become a professor. I went because
I wanted to learn more.
So if you're mainly interested in hacking and you go to grad school,
you'll find a lot of other people who are similarly out of their
element. And if half the people around you are out of their element in the
same way you are, are you really out of your element?
There's a fundamental problem in "computer science," and it surfaces
in situations like this. No one is sure what "research" is supposed to be.
of research is hacking that had to be crammed into the form of an
academic paper to yield one more quantum of publication.
So it's kind of misleading to ask whether you'll be at home in grad
school, because very few people are quite at home in computer
science. The whole field is uncomfortable in its own skin. So
the fact that you're mainly interested in hacking shouldn't deter
you from going to grad school. Just be warned you'll have to do a lot of stuff
you don't like.
Number one will be your dissertation. Almost everyone hates their
dissertation by the time they're done with it. The
process inherently tends to produce an unpleasant result, like a cake made out
of whole wheat flour and baked for twelve hours. Few dissertations
are read with pleasure, especially by their authors.
But thousands before you have suffered through writing a dissertation.
And aside from that, grad school is close to paradise. Many people
remember it as the happiest time of their lives. And nearly all
the rest, including me, remember it as a period that would have
been, if they hadn't had to write a dissertation. 
The danger with grad school is that you don't see the scary part
upfront. PhD programs start out as college part 2, with several
years of classes. So by the time you face the horror of writing a
dissertation, you're already several years in. If you quit now,
you'll be a grad-school dropout, and you probably won't like that
idea. When Robert got kicked out of grad school for writing the
Internet worm of 1988, I envied him enormously for finding a way out
without the stigma of failure.
On the whole, grad school is probably better than most alternatives. You meet a
lot of smart people, and your glum procrastination will at least
be a powerful common bond. And of course you have a PhD at the
end. I forgot about that. I suppose that's worth something.
The greatest advantage of a PhD (besides being the union card of
academia, of course) may be that it gives you some baseline confidence.
For example, the Honeywell thermostats in my house have the most
atrocious UI. My mother, who has the same model, diligently spent
a day reading the user's manual to learn how to operate hers. She
assumed the problem was with her. But I can think to myself "If
someone with a PhD in computer science can't understand this
thermostat, it must be badly
If you still want to go to grad school after this equivocal
recommendation, I can give you solid advice about how to get in.
A lot of my friends are CS professors now, so I have the inside
story about admissions. It's quite different from college. At
most colleges, admissions officers decide who gets in. For PhD
programs, the professors do. And they try to do
it well, because the people they admit are going to be working for
Apparently only recommendations really matter at the best schools.
Standardized tests count for nothing, and grades for little. The
essay is mostly an opportunity to disqualify yourself by saying
something stupid. The only thing professors
trust is recommendations, preferably from people they know. 
So if you want to get into a PhD program, the key is to impress
your professors. And from my friends who are professors I know
what impresses them: not merely trying to impress them. They're
not impressed by students who get good grades or want to be their
research assistants so they can get into grad school. They're
impressed by students who get good grades and want to be their
research assistants because they're genuinely interested in the
So the best thing you can do in college, whether you want to get
into grad school or just be good at hacking, is figure out what you
truly like. It's hard to trick professors into letting you into
grad school, and impossible to trick problems into letting you solve
them. College is where faking stops working. From this point,
unless you want to go work for a big company, which is like reverting
to high school, the only way forward is through doing what you
 No one seems to have minded, which shows how unimportant
the Arpanet (which became the Internet) was as late as
 This is why, when I became an employer, I didn't care
about GPAs. In fact, we actively sought out people
who'd failed out of school. We once put up posters around Harvard
saying "Did you just get kicked out for doing badly in your classes
because you spent all your time working on some project of your
own? Come work for us!" We managed to find a kid who had been,
and he was a great hacker.
When Harvard kicks undergrads out for a year, they have to get jobs.
The idea is to show them how awful the real world is, so they'll
understand how lucky they are to be in college. This plan backfired
with the guy who came to work for us, because he had more fun than
he'd had in school, and made more that year from stock options than
any of his professors did in salary. So instead of crawling back
repentant at the end of the year, he took another year off and went
to Europe. He did eventually graduate at about 26.
 Eric Raymond says the best metaphors for hackers are
in set theory, combinatorics, and graph theory.
Trevor Blackwell reminds you to take math classes intended for math majors.
"'Math for engineers' classes sucked mightily. In fact any 'x for
engineers' sucks, where x includes math, law, writing and visual
 Other highly recommended books: What is Mathematics?, by
Courant and Robbins; Geometry and the Imagination by Hilbert and
And for those interested in graphic design,
 If you wanted to have the perfect life, the thing to do would
be to go to grad school, secretly write your dissertation in the
first year or two, and then just enjoy yourself for the next three
years, dribbling out a chapter at a time. This prospect will make
grad students' mouths water, but I know of no one who's had the
discipline to pull it off.
 One professor friend says that 15-20% of the grad students they
admit each year are "long shots." But what he means by long shots
are people whose applications are perfect in every way, except
that no one on the admissions committee knows the professors who
wrote the recommendations.
So if you want to get into
grad school in the sciences, you need to go to college somewhere with
real research professors. Otherwise you'll seem a risky bet
to admissions committees, no matter how good you are.
a surprising but apparently inevitable consequence:
little liberal arts colleges are doomed.
high school kids at least consider going into the sciences, even
if they ultimately choose not to.
Why go to a college that limits their options?
Thanks to Trevor Blackwell, Alex Lewin, Jessica Livingston,
Robert Morris, Eric
Raymond, and several
anonymous CS professors
for reading drafts of this, and to the students whose questions