Name: 第五週 (Week 5)
Uploaded: 2021-01-14T06:43:20.000Z
Duration: 49 min 14 s

And as you may have noticed, some of the material

正如你可能已經注意到， 一些材料

is getting a little more complex, the little denser.

>> And it's very easy, especially if you've been in the habit for some time,

>> 而且它是很容易的，尤其是當 你已經在習慣了一段時間，

to be trying to scribble down most anything we do, we're saying in class.

是為了要塗下最 什麼我們做什麼，我們說在課堂上。

But realize, that is not perhaps the ideal pedagogical approach

但要意識到，這也許不是 理想的教學方法

to learning this kind of material, and material more generally.

學習這種物質， 而材料更普遍。

And so we are pleased to announce that CS50's own Gheng

因此，我們很高興 宣布，CS50自己Gheng

Gong has begun to prepare a canonical set of notes

龔已開始準備 一個規範的集合票據

for the course, the hope of which is that, one, these

用於操作過程中，希望 其是，一個，這些

not only serve as a reference and a resource

for reviewing material and going back through material that might have

審查材料中去 回通過材料可能具有的

escaped you the first time around, but also so that your heads can be more

逃脫你在第一時間左右，但 也讓你的頭可以更

up than down, when it comes time to lecture,

向上比下降，當它 談到時間來講課，

so that you might engage more thoughtfully, as

>> With that said, what you'll find on the website is such documents as this.

>> 雖這麼說，你會發現 該網站是這樣的文件，因為這。

And notice, at top left, there's not only a table of contents,

並請注意，在左上角，有 不僅表的內容，

but also time codes that will immediately jump you

to the appropriate part in the video online.

And what Chang here has done is, essentially, documented

什麼常在這裡做了 在本質上，記載

what happened in this particular lecture.

And many of the lectures are already online now with this URL.

和許多的講座是 已經在線使用這個網址。

And we'll continue to post the remainder of those by the end of this week,

我們將繼續張貼其餘 那些在本週末結束，

>> So without further ado, we started to peel back

>> 因此，事不宜遲， 我們開始剝離回

the layer that has been string for some time.

And what did we say a string actually is last week?

並沒有說什麼一個字符串 上週居然是？

And char star, well, what did that really mean?

和CHAR星，那麼， 這樣做究竟意味著什麼？

Well, all this time, if we've been calling a function,

那麼，這一切的時候，如果我們已經 被調用的函數，

like getString, and storing the so-called return

value of getString in a variable-- it's called

的getString的價值 變量 - 這就是所謂的

s type string-- we've been writing the line of code up there above.

S型string--我們已經寫 這行代碼在那裡上面。

And it's only when I see my handwriting magnified here

而且它是只有當我看到我的 在這裡手寫放大

>> However, let's assume that, on the right-hand side

>> 但是，讓我們假設， 在右手側

is, nonetheless, a reasonable depiction of what's

是，但是，合理的 一個什麼樣的描述

been going on all this time with getString.

一直在進行這一切 時間的getString。

的getString，當然，得到​​的字符串。

It means it gets a chunk of memory from the operating system

這意味著它得到了一大塊 來自操作系統的內存

通過調用一個函數，稱為malloc的。

And then it populates that chunk of memory

with the letters the user has typed in, followed by, of course,

以字母的用戶具有 當然鍵入，緊接著，，

a null character, or backslash zero at the very end.

一個空字符或反斜杠 零在最後。

>> Meanwhile, on the left-hand side of this story, all this time,

>> 同時，在左手側 這個故事，這一切的時候，

我們已經聲明了一個變量，如第

And that variable is what now will start calling a pointer.

而這個變量就是現在 將開始調用的指針。

It's not a box inside of which we put the string, Daven, per se,

這不是這裡面一箱 我們把串，Daven，本身

but rather we put in that square box on the left what exactly?

而是我們把在這方 箱體左側究竟是什麼？

>> AUDIENCE: The address of where it's located in memory.

>> 聽眾：的地址 它位於內存中。

The address of where Daven is located in memory.

And not where all of Daven is located, per se, but specifically the address

不，所有Daven的所在， 本身，而是專門的地址

>> DAVID J. MALAN: The first character in Daven, which, in this case,

>> 戴維·J·馬蘭：第一個字符 在Daven，其中，在這種情況下，

I proposed was arbitrarily and unrealistically 1, Ox1,

我提出了任意 和不切實際1，OX1，

which just means the hexadecimal number of 1.

它的意思是， 1的十六進制數。

But it's probably going to be a much bigger number

但是，它可能會 是一個更大的數字

that we might draw with a 0x as a prefix,

我們可能會得出 以0X作為前綴，

And because we don't need to know where the rest of the characters of Daven

而且，由於我們並不需要知道在哪裡 Daven的字符的其餘部分

are, because of what simple design decision that was made many years ago?

是因為，有什麼簡單的設計 決定這是多年前？

The backslash 0 allows you, albeit in linear time, to traverse the string,

反斜線0可以讓你，儘管在 線性時間，來遍歷字符串

walk from left to right, with a for loop, or a while

由左到右行走， 用for循環，或同時

loop, or something like that, and determine, oh, here

環或類似的東西 這一點，決定了哦，這裡

So with just the address at the beginning of a string,

所以只用在地址 字符串的開始，

we can access the entirety of it, because all this while,

我們可以訪問的全部 它，因為這一切的同時，

一個字符串，剛剛一個char明星。

>> So it's certainly fine to continue using the CS50 library and this abstraction,

>> 因此，這的確精緻繼續使用 在CS50庫，而且這樣的抽象，

so to speak, but we'll begin to see exactly

可以這麼說，但我們會 首先，看看到底

what's been going on underneath this whole time.

什麼是怎麼回事 下面這整個時間。

So you may recall this example, too, from last time, compare 0,

所以，你可能還記得這個例子中， 同樣，從去年的時候，比較0，

但是，我們開始解決這個問題。

>> But as perhaps a refresher, might I interest someone

>> 但是作為也許是複習， 我可能感興趣的人

in a pink elephant today, also made by Chang?

粉紅色的大象的今天， 還長呢？

怎麼樣，你在前面？ [聽不清]。

>> And in the meantime, as you come up, let's

>> 並且在此期間， 你上來，讓我們

consider for just a moment what this code was actually doing.

考慮了一會兒就好了什麼 這段代碼實際上做的事情。

It's declaring two variables up top, s and t, and calling getString.

它聲明兩個變量了 頂，S和T，並調用的getString。

This isn't a very user-friendly program, because it doesn't tell you what to do.

這不是一個非常用戶友好的程序， 因為它不會告訴你的事。

But let's just assume we're focusing on the juicy part.

但是，讓我們姑且我們 重點是多汁的一部分。

And then we do, if s equals equals t, it should say printf,

然後我們做的，如果s等於 等於T，應該說printf的，

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第五週 (Week 5)

essentially

apparently

character

random