Actually with const char* it means the pointer variable is constant, not the contents of the location pointed to by the pointer.

a is a pointer in this example

Pointer Variable Block of memory
[a]---------------------> [] [] [] [] [] [] [] [] [] [] - Starting@2000001 (say)

Now what const char* a means is that a can only point to that memory location (because it's declared a const) and not any other memory location.

If I'm wrong, somebody please correct me, but that is my understanding of pointers.

As I said before, it's all very confusing so why not just use std::string? These trivial issues are not worth bothering about when you're interesting more in the bigger picture of your program.

That is not correct Harishankar.
The const keyword applies to the object/type which is to the left handside of the keyword, if there is nothing to the left then it applies to the right.

char const* ptr: ptr is a pointer to a constant char
const char* ptr: ptr is a pointer to a constant char

char * const ptr: ptr is a constant pointer to a char


char const * const ptr : ptr is a constant pointer to a constant char.
const char * const ptr: ptr is a constant pointer to a constant char.


The easiest way to read is from right to left and put the const to the right of what it effects(in my opinion)

edit:
http://www.parashift.com/c++-faq-lit...rrectness.html

Thank you very much for the clarification. Much googling didn't help me out there.

Oh, I agree, that 'std::string' is very often nicer than a char[], but that has very little to do with the "const issue" at all. A very common case, when 'const' is advisable is, if you want to pass an object to a function by reference (to avoid the expensive call of a copy ctor), but you want also to assure that the original object doesn't change during process; example:
This is a very fundamental thing and I found that the keyword const is one of the things many people uses without thinking about; they declare 'const' here and 'const' there and if needed "const_cast" it back. This is not what 'const' was made for. If I see a function that takes a const parameter, then I trust, that this parameter don't change during process. And if I assume, that I will change a variable later, then I don't modify it with 'const'.

OK i was wrong. Thanks for the clarification.

I am still confused.


if:

char *x ="ABC";
const char *y = "DEF";

can I

A: x=y; ?
B: y=x; ?

for me A would be ok but not B. Am I rigth?

The other way round! You can always (and only) assign a non-const to const. In other words: You can always restrict, but not widen the modification.

Thanks.

I draw it up on a paper and now I get it. dmail had the explaination. I though "const char* ptr" was a constant pointer to a char but its a pointer to a constant char.

I still learn something every day.