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DAVID MALAN: All right.

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So my name is David Malan.

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And in fall of 1995, I sat
exactly where you're sitting

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right now in an economics class.

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And elsewhere on campus, I sat in
on government, and some mathematics,

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and similar related fields.

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And the reason for that was
that when I got here on campus,

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I really just gravitated toward
the familiar, the kinds of subjects

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in high school that I rather
liked and I felt I was good at.

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And computer science
wasn't even on my radar.

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In fact, it wasn't until
sophomore fall that I finally

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got up the nerve following
some friends on campus

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into a class called CS50, our
introductory course in CS,

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that I even got up the nerve
to step over that threshold.

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And the only reason I
stayed in that class

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my sophomore year was because the
professor let me enroll pass/fail.

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But over the next few months
I realized that this actually

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was a field for me and for
so many of my classmates.

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It wasn't really something to beware.

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It was absolutely a
challenge and a lot of work.

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But that was at the same time what
made it so fun and interesting.

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And to this day, I still remember
going back to Mather House on Friday

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nights when homework
assignments were released

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and diving in after dinner
time into the problem set

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just because I liked it so much.

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And so after 19 years not
really ever finding homework fun

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to find that to be the case,
I sort of found my way.

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And whether you end up majoring
in a field like computer science

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or really just taking one class,
it's just such an empowering field

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because you can go back
to the arts, humanities,

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social sciences, natural
sciences, and not only

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think a little bit
differently about those worlds

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but practically solve problems
using code or just ideas therein.

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And so what I thought I'd do
in just a few minutes here

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is give you not only a taste of this
class called CS50 but also computer

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science more generally,
which I dare say is probably

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more accessible, more familiar to
you than you might otherwise actually

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think.

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And as for CS50 itself, more than just
teach you a programming language as

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is rather the norm in
high school courses,

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especially we really do aspire
now to teach you how to program

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and how to think more methodically.

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We introduce you to a
language first called Scratch

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that you might even
remember from middle school.

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We spend time thereafter on a
language called C, and Python,

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and later in the class
we end by focusing

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on web programming or mobile
application development

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and using the tools that are inevitably
going to evolve over the coming years

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but by way of this foundation, even if
it's the only CS class you ever take,

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you can actually teach yourself
new languages thereafter

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and keep up and pick up
what new topics might arise.

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So then what is then CS
and who then are you?

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Well, according to Les Pass
Fall 2022, 2/3 of CS50 students

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have never programmed before or taken
a computer science class before.

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And so indeed if you're feeling
like that is not for me,

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realize you are and will
be in very good company.

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And I dare say CS is really just
this picture, problem solving more

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generally.

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And what's a problem?

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Well, it's something that's got input
and we need output, the solution there

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too.

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But before we can solve problems,
especially with computers,

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we just have to decide how we're going
to represent these inputs and outputs.

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And for instance, if I might want to
represent information on my human hand

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to take attendance,
well, how many people

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could I count on my one human hand?

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Five.

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Very good.

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But incorrect, because if I think
about this a little more differently,

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I could actually count as high
as I think 31 on one human hand,

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maybe not by counting like
one, two, three, four, five,

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but maybe if I come up with some kind
of pattern, maybe one, two, three--

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can't really do the next one because
it involves the middle finger

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but then it's six and
then seven and beyond.

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And so how do we get from that
simple hand to just thinking

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a little more differently about it?

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Well, let me propose that we start even
more simply with just a light bulb.

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Indeed, inside of your computer, your
phone, there's tiny little transistors,

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otherwise known as little switches
that can either be on or off.

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And you probably already
know whether or not

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you've taken a CS class before
that computers speak zeros

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and ones, the so-called binary system.

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But how do we get to
zeros and ones to counting

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to two, to three, to 31 or even higher?

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Well, we can just turn
these light bulbs on

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and count with a single light bulb, or a
single switch, or a single binary digit

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or bit from zero, if this thing
here is off, to up to a one

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if this here light bulb or switch is on.

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Well, let's take this more
simply than five fingers.

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How about three light bulbs?

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How high can you count--

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knowing that this is now indeed a
trick question-- how high can you

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count with three light bulbs?

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So OK.

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So some of you already gleaned
that it's indeed seven.

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And if you didn't,
you're in good company.

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Only a third of the audience
probably just gleaned that.

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But how do you get from three light
bulbs to counting as high as seven?

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Well, I could very familiarly
just turn these on one at a time.

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So that's one, that's two, that's three.

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But what if I take some inspiration
from permuting my fingers up and down

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in different patterns, if you will?

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Well, then I could say this is zero when
they're all off but maybe this is one,

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maybe this is two, maybe this is three,
and now four, and now five, and now

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six, and now seven.

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And even if that was a little
quickly, take my word for it

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that there were seven distinct
patterns there plus eight

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for them all being off.

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Now turns out that this system,
even if it's not obvious

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why I was turning one
on and not the other,

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is actually already familiar to us.

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This, of course, is
the human number 123.

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And you just kind of get that by
looking at these symbols on the screen.

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But that's all they are,
symbols that you and I were

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taught in like grade school to ascribe
some mathematical meaning to them, 123.

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But if we rewind some 10,
20 years, this, of course,

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you might recall is the ones place.

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This now is the tens place.

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This is the hundreds place and so forth.

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So when you see one,
two, three in that order,

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we immediately do some mental
math of 100 times 1 plus 10 times

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2 plus 1 times 3, which of course,
is 100 plus 20 plus 3, ergo 123.

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And we just kind of do
that intuitively nowadays.

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Well, computers do
exactly the same thing.

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And even though they have
just tiny little switches

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that they can turn on and off,
by way of those patterns can

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they represent any number we might like.

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So here for instance is
a three-digit value, just

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something, something
something, but notice

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that those columns, even though
your grade school teacher didn't

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talk to you about powers and exponents,
are really just 10 to the zero, 10

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to the one, 10 to the two, and so forth.

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But what if we don't give you
10 digits, zero through nine?

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We give you just zero or one, off or on?

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Well, we can just change
the base, so to speak,

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to be two so now you have the ones
place, the twos place, the fours place,

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then eight, 16, 32, and so forth.

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And so computers are using
the same system as you and me.

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They're just doing it with a
smaller, simpler even alphabet.

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And so here in binary,
zeros and ones would

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be the number we know as 0
because it's off, off, off.

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Here now is one.

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Here now is two.

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And why?

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Because there's a one
in the twos column only.

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Here now it's three because there's a
two and a one that are both one or on.

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And now of course four, and
five, and six, and seven.

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And this invites the question, well,
how do we count as high as eight

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or what is eight in binary?

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Should be 1000 but we
need more hardware.

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We need another light bulb.

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We need another switch.

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We need more memory, so to speak.

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And so if you keep giving me more
digits, more memory, more hardware,

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we can count as high
up as we might want,

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be it 31 using five digits literally
here, or maybe even 16, or 32, or 64

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nowadays as is the norm.

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So how do we represent other things if
we have different types of problems?

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Well, we could represent
letters of the alphabet.

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But if we've already decided
that everything is numbers,

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we need to agree that, OK, we need
to represent letters with numbers.

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And so it turns out
humans decades ago decided

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that this pattern of switches,
light bulbs, or bits, binary digits,

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will represent the capital
letter A in English.

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What does that translate to?

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Well, that's the 64s place.

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That's the ones place.

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So if we do some quick
math, that gives me 65.

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And that's just what every
Mac, PC, Android phone,

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iPhone nowadays has
used for now decades.

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Well, that's part of a
system we know is Unicode.

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And it can be used for other things
too like sending actual messages.

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So here's a chart of all of the
English letters, capital, lowercase,

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some punctuation, and more.

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And if you focus just on this
column, notice that 72 is H, 73 is I,

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and we started, of course, with 65
being A and everything in between.

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So if your phone were to receive
a pattern of zeros and ones,

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some kind of wireless signal
that represents this, well,

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that I will stipulate is 72, 73, 33.

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So what text message did I just receive?

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Apparently, hi.

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Now what was the 33?

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We'd have to kind of go back here.

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And it turns out it's an exclamation
point just according to the standard.

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And this is how your phone
sort of knows what to display.

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Now suppose your phone got
this pattern of zeros and ones.

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This is getting big.

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It's roughly four billion.

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But that is just another
letter of an alphabet.

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And it's not the English
alphabet in this case but anyone

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want to hazard a guess or if you've
taken CS50 online might know?

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This is a very happy face with tears of
joy, which is the most popular emoji as

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of last year but you might
notice that sometimes this

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looks like this on an iPhone or
slightly different like this on Android.

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And that's because even
emoji are just characters

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that have patterns of zeros and
ones or numbers that represent them.

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And much like we have
different fonts in the world,

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it's up to the computer, the
phone, to decide pictorially

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how this thing is going to be displayed.

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And if we thought about
it, it turns out there's

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like 64 light bulbs here in Sanders.

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And if we treated these as eight
distinct groups of binary digits,

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I bet we could even spell something
out here on the stage for all of you.

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Now me and lastly, how might
we represent other things?

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Well, in CS50, you'll learn how to
represent colors of some amount of red,

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green, and blue, for instance,
how to represent music,

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maybe some combination of
what's the note, how long do

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you want to hear it, how
loud do you want to hear it,

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so just numeric values too so it's
just a system of coding that represents

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these different types of values.

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So if we just kind of agree
for now until September

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that computers can represent inputs
and outputs using zeros and ones alone,

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well, let's lastly look at
this black box in between.

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How do we actually solve some problem?

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Well, one common problem,
for instance, might

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be this here technology, a phone book.

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And in this phone book is a whole
bunch of human names, A through Z,

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and their corresponding phone numbers.

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Now as old school as this is, it's
the exact same idea in your phones

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nowadays with the Contacts icon
of course on iPhone or Android.

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And if you think about it, if you
ever autocomplete someone's name,

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the phone is searching for that person's
name alphabetically much like I might.

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So how might I do this
in the human world

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or how might Apple or
Google do this in code?

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Well, I could start searching
one page at a time left to right.

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This is a very methodical
algorithm, step by step instruction

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for solving this problem.

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Is it correct?

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So technically yes, it is
correct, because if I'm

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looking for John Harvard, H, well, I'll
eventually get to him albeit slowly.

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All right.

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What could I do a little better?

234
00:10:53,433 --> 00:10:55,400
Maybe two, four, six, eight.

235
00:10:55,400 --> 00:10:58,400
I should probably look down
but 10, 12, and so forth.

236
00:10:58,400 --> 00:11:00,740
Is that algorithm correct?

237
00:11:00,740 --> 00:11:01,430
So no.

238
00:11:01,430 --> 00:11:03,700
Why?

239
00:11:03,700 --> 00:11:06,460
I might miss it because if I
get unlucky and John Harvard

240
00:11:06,460 --> 00:11:09,317
is sandwiched between two
pages but it's twice as fast.

241
00:11:09,317 --> 00:11:10,150
So that's appealing.

242
00:11:10,150 --> 00:11:10,720
So OK.

243
00:11:10,720 --> 00:11:14,980
Worst case, let me just double back if
I hit names starting with I instead of H

244
00:11:14,980 --> 00:11:17,497
and then I can at least solve
that bug or potential mistake.

245
00:11:17,497 --> 00:11:20,080
And we'll teach you how to solve
even more problems than that.

246
00:11:20,080 --> 00:11:21,930
But obviously, back in
the day and even now

247
00:11:21,930 --> 00:11:23,680
what Apple and Google
and others are doing

248
00:11:23,680 --> 00:11:26,500
when they search digitally is
they're metaphorically opening

249
00:11:26,500 --> 00:11:28,870
to the middle of your
contacts, looking down,

250
00:11:28,870 --> 00:11:32,260
and of course it's probably the
M section roughly halfway through

251
00:11:32,260 --> 00:11:36,100
but what do I know about John Harvard
now with respect to this phone book?

252
00:11:36,100 --> 00:11:38,030
Is he to the left or to the right?

253
00:11:38,030 --> 00:11:39,730
So left alphabetically.

254
00:11:39,730 --> 00:11:44,680
And so here in CS50 is where we can tear
this problem in half, throw half of it

255
00:11:44,680 --> 00:11:49,320
away, leaving us with maybe originally
1,000 pages, now maybe 500 pages,

256
00:11:49,320 --> 00:11:50,320
and I can do this again.

257
00:11:50,320 --> 00:11:51,653
And oh, I went a little too far.

258
00:11:51,653 --> 00:11:52,780
I'm in the F section.

259
00:11:52,780 --> 00:11:55,390
But I can again tear
the problem in half.

260
00:11:55,390 --> 00:11:58,060
Now I'm down to 250 pages.

261
00:11:58,060 --> 00:11:59,980
And we can only do this
demo once each year.

262
00:11:59,980 --> 00:12:03,778
But now I can go to 125, 67 or so.

263
00:12:03,778 --> 00:12:06,570
And I have to deal with rounding
and silly little issues like that.

264
00:12:06,570 --> 00:12:10,400
But I dare say I can eventually
get down to the H page

265
00:12:10,400 --> 00:12:12,450
and call John Harvard at that point.

266
00:12:12,450 --> 00:12:17,210
And if I started with 1,000 and I divide
it in half, dividing and conquering

267
00:12:17,210 --> 00:12:22,670
more familiarly, it turns out I can do
this in 10 total steps, not 1,000, not

268
00:12:22,670 --> 00:12:25,470
500, 10 total steps.

269
00:12:25,470 --> 00:12:29,240
And that's just a taste then of what
you'll learn in a course like CS50

270
00:12:29,240 --> 00:12:31,520
and in computer science more generally.

271
00:12:31,520 --> 00:12:35,600
Beyond that and along the way, you'll
see so much of a support structure

272
00:12:35,600 --> 00:12:40,130
at hand and indeed CS50
is distinct in so many

273
00:12:40,130 --> 00:12:41,990
of its supports so
many of your classmates

274
00:12:41,990 --> 00:12:45,860
themselves are our own teaching fellows
or TFs and course assistant CAs.

275
00:12:45,860 --> 00:12:49,040
And now that everything has been back
on campus for the past year, just

276
00:12:49,040 --> 00:12:52,790
like in olden times we've brought back
a lot of the community and supportive

277
00:12:52,790 --> 00:12:54,207
events that we've long had.

278
00:12:54,207 --> 00:12:57,290
And so I thought I'd conclude by hitting
play on this short slideshow that

279
00:12:57,290 --> 00:13:00,020
will paint a picture of what your
predecessors have experienced

280
00:13:00,020 --> 00:13:03,870
this past fall and what awaits
you too this fall as well.

281
00:13:03,870 --> 00:13:08,777
This then is CS50.

282
00:13:08,777 --> 00:13:11,222
[VIDEO PLAYBACK]

283
00:13:11,222 --> 00:13:21,002


284
00:13:21,002 --> 00:13:22,950
[VOCALIZING]

285
00:13:22,950 --> 00:13:30,018


286
00:13:30,018 --> 00:13:32,180
SPEAKER 1: (SINGING)
You're strolling along

287
00:13:32,180 --> 00:13:38,060
Mass Ave. We're sitting by Widener,
rubbing John Harvard's foot,

288
00:13:38,060 --> 00:13:46,190
wishing for the best, praying to the Ivy
gods thinking, man, what are the odds

289
00:13:46,190 --> 00:13:50,540
that Harvard is the place I'll manifest?

290
00:13:50,540 --> 00:13:53,150
Now Ivy Day has arrived.

291
00:13:53,150 --> 00:13:58,250
You're nervous as ever,
crowding around a tiny screen.

292
00:13:58,250 --> 00:14:00,636
Heart beats as you wait.

293
00:14:00,636 --> 00:14:03,080
[INAUDIBLE] and click.

294
00:14:03,080 --> 00:14:04,358
Congratulations.

295
00:14:04,358 --> 00:14:06,260
You're in.

296
00:14:06,260 --> 00:14:11,330
Oh, this, this could be the
start of something great.

297
00:14:11,330 --> 00:14:14,180
Now Visitas has come upon us.

298
00:14:14,180 --> 00:14:16,190
Let's all shop a class.

299
00:14:16,190 --> 00:14:21,230
Who knows what David Malan has in store.

300
00:14:21,230 --> 00:14:26,150
Learning Scratch, JavaScript,
CSS, SQL, C, F Flask,

301
00:14:26,150 --> 00:14:31,130
getting free food, who
could ask for more?

302
00:14:31,130 --> 00:14:35,990
Next thing you know, fall is
here and it's your first P set.

303
00:14:35,990 --> 00:14:40,236
You can't get the Scratch
cat to do its little dance.

304
00:14:40,236 --> 00:14:43,380
Oh, suddenly it's Sunday night.

305
00:14:43,380 --> 00:14:46,440
Everyone's in such a fright.

306
00:14:46,440 --> 00:14:50,370
Oh, this could be the
start of your next chance.

307
00:14:50,370 --> 00:14:52,040
You're freaking out.

308
00:14:52,040 --> 00:14:55,150
It's week two and you've
only just started.

309
00:14:55,150 --> 00:15:00,220
You're actually coding
now or so you might think.

310
00:15:00,220 --> 00:15:02,690
You've never done this before.

311
00:15:02,690 --> 00:15:05,550
That's why you can't handle more.

312
00:15:05,550 --> 00:15:09,550
You don't see how you're
going to sleep a wink.

313
00:15:09,550 --> 00:15:10,250
Don't stress.

314
00:15:10,250 --> 00:15:11,795
Your TFs are there.

315
00:15:11,795 --> 00:15:14,246
They're ready to help you.

316
00:15:14,246 --> 00:15:18,770
A legion of programmers
at your beck and call.

317
00:15:18,770 --> 00:15:24,580
When all of a sudden, you
look up and the error's gone,

318
00:15:24,580 --> 00:15:28,670
oh, maybe you can code well after all.

319
00:15:28,670 --> 00:15:35,050
Who knew that coding for the first time
would be such a rush, or the first time

320
00:15:35,050 --> 00:15:41,100
you build binary search, or that
your first day here on campus

321
00:15:41,100 --> 00:15:47,610
would be a straight flush, and
you'd go home with CS50 bucks.

322
00:15:47,610 --> 00:15:51,930
Next thing you know, winter's
here and it's the last lecture.

323
00:15:51,930 --> 00:15:56,690
You walk into Sanders and
lights start to shine.

324
00:15:56,690 --> 00:15:59,060
Well, how the semester's flown.

325
00:15:59,060 --> 00:16:02,140
Your confidence has grown.

326
00:16:02,140 --> 00:16:04,780
And this could be the
start of something.

327
00:16:04,780 --> 00:16:07,090
This could be the heart of something.

328
00:16:07,090 --> 00:16:11,110
This could be the
start of something fun.

329
00:16:11,110 --> 00:16:13,800
So fun.

330
00:16:13,800 --> 00:16:16,110
So fine.

331
00:16:16,110 --> 00:16:17,370
So fine.

332
00:16:17,370 --> 00:16:21,464


333
00:16:21,464 --> 00:16:24,908
[APPLAUSE]

334
00:16:24,908 --> 00:16:29,608


335
00:16:29,608 --> 00:16:30,650
KATIE: Thank you so much.

336
00:16:30,650 --> 00:16:34,240
We are the Radcliffe Pitches, Harvard
University's oldest treble voice jazz

337
00:16:34,240 --> 00:16:36,740
a cappella group founded back in 1975.

338
00:16:36,740 --> 00:16:39,700
And it is such an honor to be
singing with all of you tonight.

339
00:16:39,700 --> 00:16:43,267
I hope you are all enjoying
Visitas, albeit a little bit rainy.

340
00:16:43,267 --> 00:16:45,100
But if you are interested
at all in singing,

341
00:16:45,100 --> 00:16:48,100
the Pitches are actually having an
open rehearsal later this evening

342
00:16:48,100 --> 00:16:49,660
in Farkas Hall 203.

343
00:16:49,660 --> 00:16:53,650
You can join us and we promise not
to make you sing CS50 related lyrics.

344
00:16:53,650 --> 00:16:57,130
Now at this time, I'd like to invite our
sibling group, the Harvard Krokodiloes,

345
00:16:57,130 --> 00:16:58,460
on stage to join us.

346
00:16:58,460 --> 00:17:00,165
We hope you'll get a kick out of it.

347
00:17:00,165 --> 00:17:01,540
SPEAKER 2: Thanks so much, Katie.

348
00:17:01,540 --> 00:17:03,730
As Katie said, we are
the Harvard Krokodiloes,

349
00:17:03,730 --> 00:17:08,050
Harvard University's oldest a cappella
singing group founded way back in 1946.

350
00:17:08,050 --> 00:17:16,069
And we are so excited to welcome you
all, the class of 2027, to Harvard.

351
00:17:16,069 --> 00:17:19,089
Now we're going to sing just
one more song for you all today.

352
00:17:19,089 --> 00:17:22,540
But if you like what
you hear, please feel

353
00:17:22,540 --> 00:17:26,770
free to follow us on
Instagram @HarvardKrokodiloes

354
00:17:26,770 --> 00:17:30,560
or check out our TikTok, @TheKrokTalk
You can find more information

355
00:17:30,560 --> 00:17:31,580
about our group there.

356
00:17:31,580 --> 00:17:33,140
Congratulations, everyone.

357
00:17:33,140 --> 00:17:35,026
And welcome to Harvard.

358
00:17:35,026 --> 00:17:38,477
[APPLAUSE]

359
00:17:38,477 --> 00:17:44,886


360
00:17:44,886 --> 00:17:51,510
(SINGING) My story is
much too sad to be told.

361
00:17:51,510 --> 00:18:00,190
But practically everything
leaves me totally cold.

362
00:18:00,190 --> 00:18:10,160
The only exception I know is the
case when I'm out on a quiet spree

363
00:18:10,160 --> 00:18:16,310
fighting vainly the old
ennui and I suddenly

364
00:18:16,310 --> 00:18:22,580
turn to see your fabulous face.

365
00:18:22,580 --> 00:18:23,160
1, 2, 3,

366
00:18:23,160 --> 00:18:23,660
4.

367
00:18:23,660 --> 00:18:26,894
[VOCALIZING]

368
00:18:26,894 --> 00:18:33,210


369
00:18:33,210 --> 00:18:37,700
I get no kick from champagne.

370
00:18:37,700 --> 00:18:41,520
Mere alcohol doesn't thrill me at all.

371
00:18:41,520 --> 00:18:50,990
So tell me why it should be true
that I get a kick out of you.

372
00:18:50,990 --> 00:18:55,460
Some like a perfume from Spain.

373
00:18:55,460 --> 00:19:04,010
I'm sure that if I took even one sniff,
it would bore me terrifically, too.

374
00:19:04,010 --> 00:19:06,575
Yet I get a kick out of you.

375
00:19:06,575 --> 00:19:09,230


376
00:19:09,230 --> 00:19:17,698
I get a kick every time I see
you standing there before me.

377
00:19:17,698 --> 00:19:24,984
I get a kick though it's clear to
me you obviously don't adore me.

378
00:19:24,984 --> 00:19:27,520
[VOCALIZING]

379
00:19:27,520 --> 00:19:51,855


380
00:19:51,855 --> 00:19:55,315
[APPLAUSE]

381
00:19:55,315 --> 00:19:55,815


382
00:19:55,815 --> 00:19:57,150
I see you.

383
00:19:57,150 --> 00:19:58,290
You're standing.

384
00:19:58,290 --> 00:20:00,135
You're there before me.

385
00:20:00,135 --> 00:20:01,770
You're standing before me.

386
00:20:01,770 --> 00:20:10,825
I get a kick though it's clear to
me you obviously don't adore me.

387
00:20:10,825 --> 00:20:15,120
Some get their kick in a plane.

388
00:20:15,120 --> 00:20:23,310
Flying so high with some gal in the
sky is my idea of nothing to do.

389
00:20:23,310 --> 00:20:37,990
Yet I get a kick, oh I get a kick,
yes, I get a kick out of you.

390
00:20:37,990 --> 00:20:43,630


391
00:20:43,630 --> 00:20:44,320
Out of you.

392
00:20:44,320 --> 00:20:46,160
[VOCALIZING]

393
00:20:46,160 --> 00:20:48,560


394
00:20:48,560 --> 00:20:51,610
[APPLAUSE]

395
00:20:51,610 --> 00:21:05,000