DAVID MALAN: --start to implement
this notion of something
either being one or a zero.
Indeed, we could just do it over here.
You know this next demo is actually
the result of a progression of demos.
It was a few years ago where I had
always kind of talked in the abstract
about turning light bulbs on as
representing one and zero, the presence
or lack of electricity, and
then just on a whim I think,
before one year's first lecture, drove
down the road to a Target, big store
like Walmart, and grabbed
a few inexpensive desk
lamps, the kinds of things
that you would like clip
onto your shelf in college and--
DOUG LLOYD: Those are flexible, yeah.
DAVID MALAN: --and you've
got a few light bulbs.
Yeah, these little goose-neck
things, and then I just
attach them to the lectern on stage.
And then it was actually
a great demonstration
I thought, in retrospect, being able
to then literally turn the switches on
and off, all our transistors on stage,
and have something very visible,
let alone in a big space like this.
DOUG LLOYD: Right, but the CS50 is
constantly reinventing itself every
DAVID MALAN: I know,
creating work for myself.
So these are-- yes, are binary bulbs.
So you might recall, Ansel
Duff, a former advisee of mine,
and an undergraduate here
majoring in engineering sciences,
actually built these for us.
And the vision was, he machine this
long tube that held eight light bulb
sockets, and then we were really
on a kick with Hue light bulbs
that semester, which are these
Internet of Things devices where
you can actually control via an API
or application programming interface.
And you'll see, we also went on Amazon
and got these little grade school
refrigerator magnets for the one's
place, two's place, all the way up
to the 128th's place.
And so you'll see eventually
that I can take out
an iPad where Ansel wrote some software
that talks via Wi-Fi to the light bulbs
so that our student volunteers can turn
the lights on and off in a pattern.
DOUG LLOYD: And the other cool thing
about having this magnetic tube
or magnetic paint on
there is that a little bit
later on when you see a second demo of
this, where we can sort of magically
wipe the place values away--
DAVID MALAN: Dramatically
wipe the place values away.
DOUG LLOYD: And suddenly
we have the hacker edition
version of the binary bulbs problem.
DAVID MALAN: Indeed, which gets some
good like, oh, from the audience there.
Though admittedly, I
think we actually over
engineered the solution so to
speak, whereby this past year
we actually reverted to not using
Hue's, but just using old school light
bulbs and little toggle switches, which
were just so much easier to set up.
These things are great when they work,
but honestly setting up the Wi-Fi,
making sure we had our own private
network that all eight light bulbs were
on, and the iPad was working,
it was just so many variables
and it would be just awful if that
doesn't work in the first few minutes
a class when you're trying to send a
message that, hey look how simple this
is, but you can't even get it to work.
DOUG LLOYD: What was great
about a demo like this,
is you don't even need a rig as awesome
as the one that Ansel helped put
together because a lot of
schools that might be--
there's the dramatic wipe away--
A lot of schools might want
to do something like this,
but it's really easy to do
with just cell phones now,
just turning on your
flashlight or your an app--
DAVID MALAN: Indeed.
DOUG LLOYD: --or an app like that.
DAVID MALAN: And that's what I've
started doing when traveling and giving
little demonstrations like this.
It's just much easier than packing like
three big light bulbs in your suitcase,
you just ask for volunteers.
DOUG LLOYD: I can imagine getting
three of those lamps through the TSA
would be very easy.
DAVID MALAN: No.
These days, no.
So any form of lights work, or
barring that, a piece of chalk
and a one and a 0.
