int *foo;
Here, you declared a pointer variable, that can point to an int.
foo = new int [5];
Here, you've initialised the pointer variable to now point to a block of integers.
Now when you delete[] foo, you're removing the allocated memory block. Foo still exists. You can assign Foo to NULL for example, making it now a null pointer.
You can also pass pointers or references to functions, sure, you know this. BUT you can also inadvertently pass a pointer by value, and not the reference that the pointer was actually pointing too.
In c++, you can pass by reference, which is different from passing a pointer. Even though a pointer's value is a reference to something, pointer itself is still a variable.
It's a bit confusing. References are also memory addresses, but you pass them directly without wrapping them in a pointer variable.
I explain:
´´´ int pointer;
void foo(int *pointer){
} which would be foo(pointer). This will create a copy of the pointer value. Any changes done will just be for this local variable inside the function.
void foo(int &pointer){
} which would be foo(&pointer). Now any changes done to pointer or dereferencing and changing the value held by the reference pointed to by the pointer will be changing the same outside pointer variable.
´´´ ### Better explanation: https://stackoverflow.com/questions/57483/what-are-the-differences-between-a-pointer-variable-and-a-reference-variable-in
int a; int *pointer = &a; int &r = a;
a reference as another name for the same variable. It is an alias for the variable. You can &pointer to get the address of the pointer, but the address of the &r is the same as &a.
Can have arbitrary level of nested pointers to pointers, offering extra levels of indirection. References only offer one level of indirection.
Still not sure what the point of references are, except for making temp variables to pass into functions, lists, without making pointers for the original variables and dereferencing them.
char **m_adjMatrix;
m_adjMatrix = new char*[m_maxVerts];
m_adjMatrix[index1][index2] = 1;m_adjMatrix is pointer to pointer. Pointer to first dimension, can be thought. Then accessing that, you access second dimension. (the second pointer)