scis.regis.edu ● cs-362: data structures week 6 part 2 dr. jess borrego 1
DESCRIPTION
Pointer Data Type/Pointer Variables The type is integer The Name of the integer is A The address is The value stored in A is 325 int A = 325;10280 A 3 325TRANSCRIPT
Topics•Dynamic Data
▫Pointers▫Address
•Pointers to different data types•Sample programs
2
Pointer Data Type/Pointer Variables•The type is integer•The Name of the integer is A•The address is 10280•The value stored in A is 325
int A = 325; 10280
A
3
325
More Pointers
4
Running the program
5
Running the program
6
PointerAndAddress
7
Declaring Pointer Variables• Syntax:
• Examples:int *p;char *ch;
• These statements are equivalent:int *p;int* p; int * p;
8
Pointer Intro Program (I)
9
Pointer Intro Program (II)
10
Running the program
11
Pointer Intro Program (I)
12
Pointer Intro Program (II)
13
Pointer Intro Program (II)
14
MoreStruct
15
Running the program
16
MoreBeatles (I)
17
MoreBeatles (II)
18
MoreBeatles (III)
19
Running the program
20
PointerSwap
21
Running the Program
22
What happened?•The swap did not work?•The before and after are the same•Need to make sure we get the values back
to the calling program•It is calling by Value•How do we fix it?
23
Address of Operator (&)•The ampersand, &, is called the address of
operator•The address of operator is a unary
operator that returns the address of its operand
24
PointerSwap2
25
PointerSwap3
26
Running the program (I)
27
Running the program (II)
28
Dynamic Arrays•Dynamic array: array created during
the execution of a program•Example:int *p;p = new int[10];
*p = 25;p++; //to point to next array component*p = 35;
29
stores 25 into the first memory location
stores 35 into the second memory location
Dynamic Arrays (cont'd.)•C++ allows us to use array notation to
access these memory locations•The statements:p[0] = 25;p[1] = 35;store 25 and 35 into the first and second array components, respectively
30
Dynamic Arrays (cont'd.)
31
Dynamic Arrays (cont'd.)
32
Dynamic Arrays (cont'd.)• The value of list (1000) is constant
– Cannot be altered during program execution– The increment and decrement operations
cannot be applied to list• If p is a pointer variable of type int, then:p = list;copies the value of list, the base address of the array, into p– We can perform ++ and -- operations on p
• An array name is a constant pointer
33
34
Dynamic Arrays (cont'd.)
Functions and Pointers•A pointer variable can be passed as a
parameter either by value or by reference•To make a pointer a reference parameter
in a function heading, use &:void pointerParameters(int* &p, double *q){
. . .}
35
Pointers and Function Return Values•A function can return a value of type
pointer:
int* testExp(...){
. . .}
36
Dynamic Two-Dimensional Arrays•You can create dynamic multidimensional
arrays•Examples:
37
declares board to be an array of four pointers wherein each pointer is of type int
creates the rows of board
declares board to be a pointer to a pointer
PointerArray
38
PointerArray (Cont’d)
39
Running the program
40
PrintArray2D
41
PrintArray2D (Cont’d)
42
PrintArray (Cont’d)
43
Running the Program
44
Resources•Can search the internet for tutorials on
pointers•On YouTube:•http://www.youtube.com/watch?v=eFWCQ
exfaeg•From Google, search for
▫“C++ pointer tutorial“
45