blocks|key|3984145|text|它声明了3个变量。它不会初始化它们中的任何一个。它等同于写|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3984146|int+lower;
int+upper;
int+step;|code-block|syntax|javascript|3984147|所有这些变量都已声明，但它们都没有初始化。|3984148|如果你想初始化它们，你可以：|3984149|int+lower+=+0;
int+upper+=+0;
int+step+=+1;|3984150|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

It is declaring 3 variables. It is not initializing any of them. It is equivalent to writing

<pre><code>int lower;
int upper;
int step;
</code></pre>

All of these variables are declared, but none of them have been initialized.

If you wanted to initialize them, you would:

<pre><code>int lower = 0;
int upper = 0;
int step = 1;
</code></pre>

blocks|key|3984165|text|上面的代码简单地声明了三个变量。它们都没有初始化。如果你正在做面向对象的c%2B%2B，那么初始化或多或少会发生在你的构造函数中。但是如果没有，你可以稍后在函数或主体中进行初始化。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3984166|初始化将如下所示：|3984167|较低=+5；.....|3984168|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

The code above simply declares three variables. None of them are intialized. If you are doing object orientted c++ then the intialization would more or less take place in your constructor. But if not you can pretty much intialize later in the function or main body.

intialization would look like:

lower = 5;
.....

blocks|key|3984185|text|像这样声明这些变量对于输入变量的值是必要的，即|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3984186|cin>>下部；cin>>上部；|3984187|这与初始化它们不同，即|3984188|int+upper=+4；|3984189|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|L|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|M|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

Declaring these variables like so are necessary for inputting a value for the variable
i.e.

cin>> lower;
cin>> upper;

This is different then initializing them
i.e.

int upper= 4;

blocks|key|3984207|text|该代码简单地声明了变量lower、upper和step，在内存中保留了空间，以便将数据存储在这些变量中。除非变量是在全局作用域中声明的，否则它不会为它们赋值。在C%2B%2B中，这些未初始化变量的值是undefined；实际上，这意味着这些变量的值实际上是随机的，只需由为这些变量保留的内存位置中存在的任何剩余值确定即可。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3984208|如果要在声明时为多个变量赋值，可以将赋值放在与声明相同的行中：|3984209|int+lower+=+0,+upper+=+100,+step+=+1;|code-block|syntax|javascript|3984210|或者，您可以稍后为它们赋值，可能是从input语句中：|3984211|int+lower,+upper,+step;
cin+>>+lower+>>+upper+>>+step;|3984212|entityMap|0|LINK|mutability|MUTABLE|url|https://en.wikipedia.org/wiki/Undefined_behavior^0|B|5|H|5|N|4|2O|9|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@$9|15|A|16|1|17]]|E|$]]|$1|F|3|G|5|6|7|18|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|19|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1A|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|1B|8|@]|D|@]|E|$K|L]]|$1|Q|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]]]

The code simply declares the variables <code>lower</code>, <code>upper</code>, and <code>step</code>, reserving space in memory to allow data to be stored in these variables. Unless the variable is declared in the global scope, it does not assign any value to them. In C++, the values of such uninitialized variables are <a href="https://en.wikipedia.org/wiki/Undefined_behavior" rel="nofollow">undefined</a>; in practice, this means that these variables will have values that are effectively random, determined simply by whatever leftover values exist in the memory locations reserved for these variables.

If you want to assign values to multiple variables as they are declared, you can put the assignments into the same line as the declaration:

<pre><code>int lower = 0, upper = 100, step = 1;
</code></pre>

Alternatively, you can assign them values later, perhaps from an input statement:

<pre><code>int lower, upper, step;
cin &gt;&gt; lower &gt;&gt; upper &gt;&gt; step;
</code></pre>

blocks|key|3984214|text|#include+<iostream>

using+namespace+std;+
int+main(){

//Declaration+of+variables;+always+includes+a+data+type+before+the+variable+name.+++
int+lower;
int+upper;+
int+step;

//In+this+example,+"int"+is+the+data+type.+

//Example+of+initialization:+
lower+=+0;+
upper+=+5;+
step+=+1;+
}

//"lower"+has+been+initialized+to+0.+
//"upper"+has+been+initialized+to+5.+
//"step"+has+been+initialized+to+1.+|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|3984215|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>#include &lt;iostream&gt;

using namespace std; 
int main(){

//Declaration of variables; always includes a data type before the variable name. 
int lower;
int upper; 
int step;

//In this example, "int" is the data type. 

//Example of initialization: 
lower = 0; 
upper = 5; 
step = 1; 
}

//"lower" has been initialized to 0. 
//"upper" has been initialized to 5. 
//"step" has been initialized to 1. 
</code></pre>

I saw this line in a C++ code, I've just started C++ and I don't know what the line below does! I'm guessing its defining three variables lower, upper, and step that I don't have to initialize later? i.e.: lower =3, upper=4?
My Code in Question:
<pre><code>int lower, upper, step;
</code></pre>

Variable Definition in C++, defining 3 variables?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我在C++代码中看到了这一行，我刚刚启动了C++，我不知道下面这行是做什么的！我猜它定义了三个变量lower，upper和step，我以后不需要初始化了？即: lower =3，upper=4？我的代码有问题：int lower, upper, step;

问在C++中定义变量，定义3个变量？
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回答 5

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问在C++中定义变量，定义3个变量？
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