An error from other projects which impress me most

I cannot remember what the specific c++ project is, but what impressed me most is the definition of constant pointer.

If we want to define a pointer which the address content is able to change, we can‘t use char const * p, for example:

1. char const *p;
2. p=str;
3. *p=‘n‘;

we will get an error message:

错误： 向只读位置‘*p’赋值

char * const p; //define a pointer which the address is unable to change
char const * p；//define a pointer which the address content is unable to change 
const char *p； //the same as char const *p