Pointer dereference

Learn to access the value a pointer points to with *.

Pointer dereference

The * operator (dereference) accesses the value at the address a pointer holds. After int* p = &x;, writing *p reads the value of x.

* is used not only to read but also to write. Writing *p = 20; sets x's value to 20, because p holds x's address. This is the basis of pass by pointer and one of the strongest features of pointers.

Dereference assignment

By writing *p = value;, you change the variable the pointer points to. This is like using the pointer as a 'remote control'; even if p is in another function, *p affects the original variable.

This feature is used so functions can modify the caller's variables. For example void setToZero(int* p) { *p = 0; } resets the variable whose address was passed. Pointer parameters resemble reference parameters in this regard.

Exercise Modify through a pointer

Declare int x = 10;. Bind with int* p = &x;. Change x's value by writing *p = 20;. Print x with std::cout.

Show example solution

#include <iostream>

int main() {
    int x = 10;
    int* p = &x;
    *p = 20;
    std::cout << x << "\n";
    return 0;
}

Test yourself

What does this code print?
```
int x = 10;
int* p = &x;
*p = 20;
std::cout << x;
```
- Error
- 10
- 0
- 20
Show answer

20 — *p = 20 makes x become 20, because p points to x.
Match each expression to its meaning

*p

Access value
*p = 20

Change value
int* p = &x

Binding
x

Target variable
Dereference
```
std::cout << ____;
```
Show answer
```
std::cout << *p;
```

Next lesson: nullptr

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies