This article contains many errors, I just list them simply.
http://www.cnblogs.com/dolphin0520/archive/2011/04/18/2020248.html

BTW About const concept in C/C++, I have 2 articles.
《c专家编程》阅读笔记-关于const指针 http://sunxiunan.com/?p=1161
技术笔记-关于c/c++中的const http://sunxiunan.com/?p=870

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“但是程序中使用过多的const，可能在对代码的阅读时增加一定的难度”
Can’t understand. This idea is so strange.
If possible, you should use const as possible. It is a good contract.

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const int n; 这种声明方式是错误的
This definition method is wrong. (should NOT declaration!)
extern char* const p; // this is declaration, p as extern variable

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指针常量:即指针本身的值是不可改变的，而指针指向的变量的值是可以改变的;
I never heard the concept “指针常量”, it should be “the pointer points to constant” 指针指向常量!!

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“C语言和C++中的const有很大区别。在C语言中用const修饰的变量仍然是一个变量;而在C++中用const修饰过后，就变成常量了。
const int a=3; int *pa=&a; *pa=4; printf(“%d\n”,*pa); printf(“%d\n”,a);
这种情况在C++中是不允许的，原因在于a用const修饰后，已经成为常量了，因此是不允许被修改的，无论是显示的更改a的值或是通过其它方法修改它的值都是不允许的。”

!!!! WTF !!
C++ has a keyword const_cast !!

Try following code:
const int a=3;
int *pa= const_cast < int * > (&a); *pa=4;
printf(“%d\n”,*pa);
printf(“%d\n”,a);

Will print out “4 4” as result.