Name: 計算思維與Scratch--計算機科學入門--哈佛的CS50（2018年 (Computational Thinking & Scratch - Intro to Computer Science - Harvard's CS50 (2018))
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DAVID MALAN: This is CS50, Harvard University's introduction

to the intellectual enterprises of computer science

My name is David Malan, and if you are among those

in the room who are thinking, why am I in a class of computer science,

realize that I too felt that exact same way.

In fact, my freshman year, I didn't quite

get up the nerve to take this class or computer science more generally,

and that was largely because I was intimidated by it.

And I really didn't know at the end of the day what it actually was.

But realize if you, too, are feeling a little bit of that,

or even if you're among those more comfortable who

have dabbled in computer science or programming,

realize that there's so many blanks that we can fill in along the way

so that ultimately, at the end of the semester, everyone

And until then, rest assured that 68% of the people sitting to your left

and to your right and behind and in front

have never taken a CS course before, which may very well be

But realize, too, that with such an amazing support

structure with so many office hours and sections and materials and beyond,

realize that what's ultimately important in this course

is not so much where you end up relative to your classmates

in week 10, our final week, but where you end up relative to yourself

And as it turns out, computer scientists start counting at zero.

And so over the next 11 weeks, we will take you

from being among those less comfortable or perhaps

somewhere in between less comfortable and more

to feeling much more comfortable and confident and capable than that.

But to get there, we need to understand what computer science really is.

And this was something I didn't understand until I set foot in a room

And I dare say we can distill computer science into just this picture.

Computer science is about problem solving.

And I know that high school courses typically do kind of paint

a misleading picture that it's only about

and it's entirely about programming and people with their heads

down in the computer lab working fairly anti-socially on code,

but the reality is it's all about solving problems, and very often,

solving problems collaboratively either in person or by leveraging code,

programs that others have written in the past.

And what does it mean to solve a problem?

So there's a problem you're trying to solve.

And the sort of secret sauce of computer science

is going to be everything in this proverbial black box

in the middle over the next several weeks,

where you begin to understand exactly what you can do with that.

But in order to start solving problems, we kind of just

need to decide as a group how we're going to represent these problems

Well, in this room, there's a whole bunch of people.

If we wanted to take attendance or count the number of people in this room,

I might need to start keeping track of how many people I see.

But how do I represent the number of people I see?

Well, I can do it sort of old school and I can just take out a piece of chalk

I can do little stylistic conventions like that

Or I can, of course, just do that on my own hand.

But obviously, how high can I count on just one hand?

So 5 you would think, but that's just because we haven't really

It turns out that with just these five fingers, let alone these five more,

I can actually count rather higher because after all, the system

I'm using of hashmarks on the board or just

now with my fingers is just kind of keeping my fingers down and putting

But what if I actually took into account the order of my fingers

and sort of permuted them, so to speak, so that it's really patterns of fingers

that represent the number of people in the room,

and not just the mere presence of a finger going up or down.

But what if two is not just this, the obvious?

That's going to lead us to four somewhat offensively.

But if we begin to jump ahead to five, I might now

And if I want to now represent six, I could do this.

In other words, I've expressed so many more patterns on my hand already

and if we keep doing this, I think I can actually

represent painfully perhaps like 32 different patterns, and therefore

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計算思維與Scratch--計算機科學入門--哈佛的CS50（2018年 (Computational Thinking & Scratch - Intro to Computer Science - Harvard's CS50 (2018))

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