POINTERS AND MEMORY ACKNOWLEDGEMENT: THE SLIDES ARE PREPARED FROM SLIDES PROVIDED BY NANCY M. AMATO AND JORY DENNY 1

POINTERS  Pointers are variables storing the memory address of another data/variable/object. 0x000x040x080x0C0x100x140x180x1C0x20 2

POINTERS  Pointers are variables storing the memory address of another data/variable/object.  int x=5; 5 x 0x000x040x080x0C0x100x140x180x1C0x20 3

POINTERS AND MEMORY  Pointers are variables storing the memory address of another data/variable/object.  int x=5;  int *y = &x;  Operator & gives the memory address of a variable/object 5 xy 0x04 0x000x040x080x0C0x100x140x18 0x1C0x20 4

POINTERS AND MEMORY  Pointers are variables storing the memory address of another data/variable/object.  int x=5;  int *y = &x;  Operator & gives the memory address of a variable/object  int* z = y; 5 xy 0x04 0x000x040x080x0C0x100x140x18 0x1C0x20 5 z 0x04

POINTERS AND MEMORY  int *y = &x;  int* z = y;  What will happen if I write: *z = 0; ? 5 xy 0x04 0x000x040x080x0C0x100x140x18 0x1C0x20 6 z 0x04

POINTERS AND MEMORY  int *y = &x;  int* z = y;  What will happen if I write: *z = 0; ?  * is a dereferencing operator – gives the content of the memory address pointed by (or stored in) the pointer 0 xy 0x04 0x000x040x080x0C0x100x140x18 0x1C0x20 7 z 0x04

MEMORY ALLOCATION – NEW OPERATOR  new allocates space to hold the object.  new calls the object’s constructor.  new returns a pointer to that object.  Point * A = new Point (10, 20); 8

MEMORY DEALLOCATION – DELETE OPERATOR  For every call to new, there must be exactly one call to delete.  Point * A = new Point (10, 20); //allocates memory  …  delete A; //deallocates or frees the memory 9

POINTERS AND ARRAY  An array can act as a pointer  Array name is a pointer to first element in the array  Pointer can be indexed like an array  int arr[5] = {1,2,3,4,5};  cout << arr[2] << "," << *(arr+2); //displays 3,3 10

DYNAMIC ALLOCATION & DEALLOCATION OF ARRAY  Static allocation:  You must know the size of the array before hand  int arr[10];  Dynamic Allocation  Size of the array can be passed as a variable  size_t sz = 10;  int* arr = new int[sz];  Deallocate : delete[] arr; 11

MEMORY 12 MEMORY HEAPSTACK

STACK VS. HEAP  Heap – Dynamic Allocation  Point *p = new Point(5,10);  double *amount = new double[5];  Stack – static allocation  Point p(5,10);  double amount[5]; 13 What happens when p goes out of scope?

PAIR PROGRAMMING  Driver – One at the keyboard  Navigator – Helps direct driver  Teamwork and communication are key here  Switch roles frequently! 14