new[]
delete[]
C++ does NOT keep track of the size of an array

declare a dynamic array:
datatype *variablename;
example:
int *a;

allocate memory:
int size;
...
variable = new datatype[size];
a = new int[size];

size can be ANY expression. (in static has to be a constant expression)

using dynamic arrays:
- just like any other array!
cout << a[0];
cin >> a[0];
for (int j=0;j<size;j++) cout << a[j];

after using: deallocate:
delete[] a;