什么是“使用”新" C ++中的运算符。 [英] what is use of " New" operator in C++.

问题描述

大家好



我是C ++的新手，请看下面的代码

Hi all

I am new to C++ can you please see code below

int main()
{
      int *p;

      *p=100; //line 4

       cout<<* p;
}

输出：





1）如果我们可以直接给它确定new operator的用法。

2）由于指针只存储变量的地址，那么我们如何才能将变量赋值给它呢？



提前谢谢。

Output:
100

1) if we can assize it directly what is the use of "new operator" then.
2)As pointer just store a address of variable then how can we assize a variable to that?

Thanks in advance .

推荐答案

除非你使用的是一个非常糟糕的编译器，否则它会胜利你说的是：在编译时初始化之前会出现p的警告，执行时会出现运行时错误到同样的效果，然后是你正在访问内存的第二次运行时错误你不应该继续。



既然你没有在任何时候给p赋值，它将保持为零 - 并且记忆在该位置不属于您，它受到保护，您无法读取或写入。

如果您这样做，您将获得有效的结果：

Unless you are using a spectacularly poor compiler that won;t do what you say: you will get a warning that "p" is being used before it is initialised when you compile, and a run time error to the same effect when you execute, followed by a second run time error that you are accessing memory that you shouldn't if you continue anyway.

Since you don't assign a value to "p" at any point, it will remain at zero - and memory at that location is not yours, it's protected and you can't read or write to it.
You would get a valid result if you did this:

int *p;
p=(int*)100;
cout<< p;

但这不会打印100：它会打印00000064，因为默认情况下指针会打印为十六进制值。

But that wouldn't print "100": it would print "00000064" because pointers are printed as hexadecimal values by default.

参见 http://msdn.microsoft.com/en-us/library/kewsb8ba.aspx [ ^ ]。

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