Pointer to a given memory address -C++

Question

basic syntax of pointers: *ptr= &a

here &a will return the memory address of variable a and *ptr will store value of variable a

I want to ask, is it possible to make a pointer return a value from a given memory address? if yes what's the syntax

It seems that you should pick up a [decent introductory book on the subject](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list). The syntax, etc. of pointers will be covered in the first few chapters... — Oliver Charlesworth, Mar 16 '14 at 16:01
For information on Pointers : http://www.cplusplus.com/doc/tutorial/pointers/ — Crystal Meth, Mar 16 '14 at 16:01
The syntax: `ptr = &a;`, note there is no '*' unless `ptr` is a pointer to a pointer. — Thomas Matthews, Mar 16 '14 at 16:10
Pointers do not "return" anything; they are not functions. Please be clearer about your requirements. — Lightness Races in Orbit, Mar 16 '14 at 16:10

score 1 · Answer 1 · answered Mar 16 '14 at 16:12

1

Yes, you can construct a pointer that refers to some arbitrary address in memory, by initialising the pointer with the address directly, instead of with an expression like &a:

int* ptr = (int*)0x1234ABCD;  // hex for convenience
std::cout << *ptr;

Be careful, though, as it is rare that you know such a memory address exactly.

The cast (int*) is required as no implicit conversion exists between int and int*.

answered Mar 16 '14 at 16:12

Lightness Races in Orbit

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Are embedded systems rare? As this is very frequently used to access hardware registers. :-) – Thomas Matthews Mar 16 '14 at 16:12
@ThomasMatthews: Yes, I am aware of that. I use them daily. That's why I said "rare" not "never". That is _one_ use case and frankly I'm not aware of any others. That's why I said it's rare. – Lightness Races in Orbit Mar 16 '14 at 16:13

riklund · Answer 2 · 2014-03-16T16:10:11.053

0

Yes. Use the dereference operator *. For example;

int * a = new int;
int * b = new int;
*a = 5;
// Now a points to a memory location where the number 5 is stored.
b = a; //b now points to the same memory location.
cout << *b << endl; ///prints 5.
cout << a << " " << b << endl; //prints the same address.

int * c = new int;
c = *a;
// Now c points to another memory location than a, but the value is the same.
cout << *c << endl; ///prints 5.
cout << a << " " << c << endl; //prints different addresses.

edited Mar 16 '14 at 16:10

answered Mar 16 '14 at 16:01

riklund

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but here we're directly providing value to *a , instead of this i want to provide some memory address to *a , and make it store that value – user3425996 Mar 16 '14 at 16:05
Oh I see. I'll add this. – riklund Mar 16 '14 at 16:06

Pointer to a given memory address -C++

2 Answers2