Data Structures w

1. Data Structures w/C++ Dick Steflik Pointers & Dynamic Arrays

2. Static and Dynamic Memory Static Allocation allocated by the compiler at compile time once allocated, does not change Dynamic Allocation allocated by program at run time �new� allocates desired amount from heap amount depends on class/type �delete� deallocates an object and returns to storage manager for reallocation

3. Where or When Static data stricture sizes are fixed little chance for storage needs to grow prototypes Dynamic amount of data changes from run to run data relationships change frequently

4. Pointers a built-in primitive type; 32 bit used to hold the storage address of a variable to define a pointer variable use the * operator in the definition

5. Pointers (cont.) To assign a value to the pointer variable use the address operator &

6. Pointers (cont.) Note that F15 has not been assigned a value yet to do this we must use the dereferencing operator *

7. Pointers (cont.) Which is exactly equivalent to:

8. The Big Deal.... We�ve been looking at the trivial case Pointers to primitives aren�t very useful things get more interesting with arrays we can make : an array that grows as the application needs more room for data an array that shrinks as the application needs less room for data and much better with dynamic objects

9. More Pointers

10. Pointers to arrays The name of an array is a pointer to the 0th element of the array (the beginning of the array)

11. Pointers to arrays Pass by reference - in C++ arrays are always pass by reference (there is no pass by value for an array) this is a big improvement over C in C to pass an array to a function it had to be passed by passing a pointer to the beginning of the array then doing pointer arithmetic to manipulate the contentsd of the array

12. new returns the address of a piece of dynamically allocated storage

13. Dynamic Arrays arrays can be allocated at run time

14. Dynamic Arrays You can effectively change the size of an array at run-time if it was originally allocated dynamically.

15. Value semantics The value semantics of a class determine how values are copied from one object to another. In C++ the value semantics consist of two operations: the assignment operator the copy constructor The copy constructor is a constructor that creates and initializes an object to the value of another (existing) object the copy constructor has one parameter whose type is the same as the class name

16. Copy Constructor

17. Overloaded assignment operator The overloaded assignment operator must do a deep copy of all of the state variables