Chapter 09 Pointers

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Copyright 2012 Pearson Education, Inc.Copyright 2012 Pearson Education, Inc.

Chapter 9:

Pointers


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9.1Getting the Address of a Variable


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Getting the Address of a

Variable Each variable in program is stored at a

unique address

Use address operator

&to get address ofa variable

int num = -99;

cout


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9.!Pointer Variables


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Pointer Variables

Pointer variable "ften #ust called apointer$ it%s a variable that holds anaddress

&ecause a pointer variable holds theaddress of another piece of data$ it 'points'

to the data


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(omething )i*e Pointers Arra+s

,e have alread+ -or*ed -ith something similarto pointers$ -hen -e learned to pass arra+s asarguments to functions.

or e/ample$ suppose -e use this statement topass the arra+ numbersto the showValuesfunction

showValues(numbers, SI!";


7/55Copyright 2012 Pearson Education, Inc.Copyright 2012 Pearson Education, Inc.

(omething )i*e Pointers Arra+s

0he #aluesparameter$ in the showValues

function$ points to the numbersarra+.

22 automaticall+ storesthe address of numbersin

the #aluesparameter.



(omething )i*e Pointers

3eference Variables

,e have also -or*ed -ith something li*e pointers-hen -e learned to use reference variables.(uppose -e have this function

#oid $et%rder(int &donuts" cout



(omething )i*e Pointers

3eference Variables

0he donutsparameter$ in the $et%rderfunction$

points to the ell).onutsvariable.

22 automaticall+ stores

the address ofell).onuts in the

donutsparameter.



Pointer Variables

Pointer variables are +et another -a+ using a

memor+ address to -or* -ith a piece of data.

Pointers are more 'lo-4level' than arra+s andreference variables.

0his means +ou are responsible for finding the

address +ou -ant to store in the pointer and

correctl+ using it.



Pointer Variables

5efinition

int intptr;

3ead as6intptrcan hold the address of an int7

(pacing in definition does not matter

int intptr; // same as abo#eint intptr; // same as abo#e



Pointer Variables

Assigning an address to a pointer variableint intptr;

intptr = &num;

8emor+ la+outnum intptr

01 2x3a22

address of num 2x3a22



0he ndirection "perator

0he indirection operator :; dereferences

a pointer.

t allo-s +ou to access the item that the

pointer points to.

int x = 01;

int intptr = &x;

cout


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Copyright 2012 Pearson Education, Inc.Copyright 2012 Pearson Education, Inc.941=


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9.>0he 3elationship &et-een Arra+s

and Pointers


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0he 3elationship &et-een

Arra+s and Pointers

Arra+ name is starting address of arra+

int #als45 = 3, 6, 77;

cout


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0he 3elationship &et-een

Arra+s and Pointers Arra+ name can be used as a pointer

constant

int #als45 = 3, 6, 77;

cout


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Copyright 2012 Pearson Education, Inc.Copyright 2012 Pearson Education, Inc.94!?


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Pointers in E/pressions

Givenint #als45=3,6,77, #alptr;

#alptr = #als;

,hat is #alptr 8 7@ t means :address in

#alptr; 2 :1 siBe of an int;

cout


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Arra+ Access

Arra+ elements can be accessed in man+ -a+s

Arra+ access method E/ample

arra+ name and 45 #als405 = 76;

pointer to arra+ and 45 #alptr405 = 76;

arra+ name and subscript

arithmetic

(#als 8 0" = 76;

pointer to arra+ andsubscript arithmetic

(#alptr 8 0" = 76;


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Arra+ Access

onversion #als4i5is equivalent to

(#als 8 i"

Co bounds chec*ing performed on arra+access$ -hether using arra+ name or a

pointer


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rom Program 94D


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9.Pointer Arithmetic


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Pointer Arithmetic

"perations on pointer variables

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"peration E/ampleint #als45=3,6,77;int #alptr = #als;

88, -- #alptr88; // points at 6#alptr--; // now points at 3

8, - :pointer and int; cout


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rom Program 949


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9.

Chapter 09 Pointers

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