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[? LADORE: ?] My name
is [? Ladore. ?] I'm 21.

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I'm from Israel.

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And my question is I would
love to know some more

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information about how your walk-through
videos for various problems sets

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are written.

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Right now I am on problem
set five, and I'm not

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sure about most of the questions there.

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And I'm sure the
walk-through videos helped me

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a lot to understand some of those
basics and ideas of the code.

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So, generally, what
are your considerations

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and/or inspirations when
making one of those videos,

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and how do you decide what to include
in them or what not to include?

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SPEAKER 2: That's a
really good question.

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I can speak, perhaps,
to some of the history

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and then have Brian elaborate on
his particular approach to them.

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So we've been doing
these walk-through videos

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for CS50, which are these
short YouTube videos that

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are embedded into the
homework assignments

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for CS50 itself, for those unfamiliar,
for, probably, 10 plus years now.

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And different Teaching Fellows or
TFs have led them over the years.

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[? Martin ?] [? Bralek ?] was
the first some 10 plus years ago,

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Tommy MacWilliam, after that, who you
might remember from other CS50 videos,

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and then Zamyla Chan, who
held the title for, probably,

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eight or so years while she was an
undergraduate as well as a PhD student

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at Harvard.

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And she only just recently
moved out into the real world.

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In fact, as an aside, before
I forget, those of you

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who know Zamyla from past years of CS50,
I've just pasted into the chat window

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a URL of her graduation speech that
she gave upon receiving her PhD.

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But the motivation for
the walkthroughs early on

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was really to start to answer a
frequently asked question or FAQ, which

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was quite simply, where do I begin?

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I had hoped we have fairly detailed
specifications in the problem sets,

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telling students what they
ultimately need to do.

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But they deliberately don't really
tell the students how to do that,

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and, frankly, we have found
through trial and error

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that the longer, the longer, the longer
the problem sets, English language,

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gets, the less, the less,
the less the students

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actually read it, even the
native English speakers.

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And so we wanted to use
another media format

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to convey ideas and hints
for those students who

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might want the additional guidance.

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Early on, these walkthroughs
were only in person.

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We would hold them in a
lecture hall on campus,

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and students would come and
attend these classes for help

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with the current week's problem set.

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And then over the years,
we began to film those.

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And then over the years further,
we then got rid of the audience.

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And we started to pre-produce the
videos in a studio or in an office,

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just so that we could
get them just right.

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We could alternate between text and
code and the human speaking on screen,

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and then, literally, integrate them
into the problem sets themselves.

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In fact, it's a very deliberate,
if subtle, design decision

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that when Brian leads them
and Zamyla leads them,

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they're against this white
backdrop because we really

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want the human element to blend
into the homework assignment itself.

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And, indeed, what was wonderful
about Zamyla, especially,

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who really became the face of these
walkthroughs for so many years,

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students really began to identify
with her, really want to meet her,

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really want to be her because she was
literally the person there for them

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in their time of need when they were
struggling with homework assignments.

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And so that's some of the history,
and Brian has now taken up the baton

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himself.

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And, Brian, do you want to
elaborate on your approach?

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BRIAN YU: Yeah.

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Certainly, I took a lot of inspiration
from Zamyla's walk-through videos

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and watching the way that
she did them as well.

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But my general approach
with the walkthroughs

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is to, first and foremost, convey
any background knowledge needed

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to solve the problems--
that a lot of our problems

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connect computer science
to other domains.

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So with the election problems and the
problems [INAUDIBLE],, for example,

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I'll start the walkthrough
just by talking

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through how these elections work so that
you understand what the election even

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is before you start worrying about
the code, or, likewise, with speller,

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trying to talk through how a hash table
works to get an understanding of that

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before you start writing the code.

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And then the next step in
the walk-through videos

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is I try to provide some ideas for how
to start thinking about the problem

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a little bit more methodically.

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With a lot of these problems,
I've been helping students

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with them for five or so years now.

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And I've started to see the
way that some people try

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to start to think about the problem, and
so part of the goal of the walkthrough

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is in my mind is to
provide some guidance

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and some hints as to where to start your
thinking in terms of how you can then

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translate that into code while still
leaving the core of the problem

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up to you to solve because we
don't want to give the problem away

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in the walk-through video.

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But we do want to just give
you that little first nudge

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so that you have an idea of how you
can begin writing up your own solution

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and thinking about how
you would go about solving

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any of the problems in
the problem [INAUDIBLE]..

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