Pointers are variables, that hold adress (position in memory) to another variable. They can also point nowhere (null pointers).
It is declared using this syntax: pointer_type* pointer_name;
Using address-of operator &, you can get adress of any object and store it in pointer .
int n;
int *pointer_to_n = &n;
This will create a pointer pointer_to_n to our integer variable n. Now we have two different variables, that are essentialy using the same data. That means we can dereference pointer_to_n by using dereference operator * and gain access to n.
new and new []This keyword is used to allocate new memory for single variable, like this:
int* pointer = new int;
Or for allocating an array, which size can be specified while the program is running:
int size = 5;
int* pointer = new int[size]; /// Creates array of size 5
delete and delete []After you stop using the variable, you need to deallocate it. If you do not, then it will remain in memory after you exit the application.
It’s required to pair new \ delete and new [] \ delete []. If you use delete with new [], then only the first element. Using delete [] and new produces memory error.
int* dynamic_variable = new int;
int* dynamic_array = new int[5];
delete dynamic_variable;
delete[] dynamic_array;
You can also use pointers to point to another pointer. For example, when you are creating an array or arrays. However, if you do so, you need to allocate (or deallocate) every ‘step’ on it’s own. In case of array of arrays like this:
int size = 10;
/// Allocation
int** array = new int*[size];
for (int i = 0; i < size; i++) array[i] = new int[size];
/// Deallocation
for (int i = 0; i < size; i++) delete[] array[i];
delete[] array;