1. Pointer Basics
Psst… over there

2. Pointers Pointer : data type with value that is a memory address
x is a pointer
Stores location to find value
Our name
Memory location
Value
0x00
0x01
12.5 x
0x02
0x03
0x04

3. Declaring a Pointer * in a declaration means "pointer to"
x can point to an integer value:
y can point to a double value:

4. Value Uninitialized pointers point to random location
What value does p point to?
Our name
Memory location
Value
0x00
0x01
100 p
0x02
0x38232
0x03
0x04

5. Getting Addresses & is address of operator
&x "Give me the memory address of x"
&x  0x01
Our name
Memory location
Value
0x00 x
0x01
100 p
0x02
0x38232
0x03
0x04

6. Initializing Pointers
Use address of a variable to set pointers
Our name
Memory location
Value
0x00 x
0x01
100 p
0x02
0x03
0x04

7. Using Pointers Can work directly with pointers Value = copies
<, > == compare the memory locations
Our name
Memory location
Value
0x00 x
0x01
100 p
0x02 q
0x03
0x04

8. Accessing Pointees * is the dereference operator *p says Value
Outside of variable declarations
*p says
"Give me the value at the address in p"
Our name
Memory location
Value
0x00 x
0x01
100 p
0x02 q
0x03
0x04

9. Dereferenced Can use dereferenced address to get or set value Value
Our name
Memory location
Value
0x00 x
0x01
100 p
0x02
0x03
0x04

10. Dereferenced Can use dereferenced address to get or set value Value
Our name
Memory location
Value
0x00 x
0x01
200 p
0x02
0x03
0x04

11. Dereferenced Can use dereferenced address to get or set value Value
Our name
Memory location
Value
0x00 x
0x01
200 p
0x02
0x03
0x04

12. Pointer to Pointer Can point to a pointer Value
Address of the address of a value
Two dereferences to access
Our name
Memory location
Value
0x00 i
0x01
200 p
0x02
0x1 q
0x03
0x2
0x04
int i = 5;
int* p = &i;
int** q = &p;
cout << q << endl ; //2
cout << *q << endl ; //1
cout << **q << endl ; //200

13. NULL Pointers NULL means nothing C C++ NULL pointer points to nothing
NULL is keyword that has value 0
C++
NULL usually works, but supposed to use nullptr or 0

14. Using NULL
NULL or 0 used to safely indicate pointer does not have a pointee
p = NULL; //C style
p = 0; //older C++
p = nullptr; //modern C++
if(p) {
//only get here if not null/0 }

15. Syntax Issues

16. * Location These two both say x is a pointer to an int:
Type: Pointer to Int
Name: X

17. * Location
BUT, This says
x stores a pointer to an int
y stores an int

18. Typedef Typedef can eliminate some syntax issues
int* x, y; //x is a pointer to an int, y is an int
int *x, *y; //x and y both pointers to ints
typedef int* intPtr; //intPtr means int*
intPtr x, y; //x and y both pointers to ints

19. Const & Pointers Pointer's value (address) can be constant
Can't change where it points
Values they point to can be constant
Can't change the value of whatever it points to

20. Read Backwards p1 is a constant pointer to an int
Can't point at a new location
Value we are pointing to can be changed

21. Read Backwards p1 is a pointer to an int that is constant
Can point at a new location
Value we are pointing to cannot be changed

22. Read Backwards p1 is a constant pointer to an int that is constant
Cannot point at a new location
Value we are pointing to cannot be changed

23. Read Backwards
Const vars must be pointed to with const value pointers: