Chapter 7 Pointers unimap

8/18/2019 Chapter 7 Pointers unimap

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Pointer

CHAPTER 7


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OutlineIntroductionWhat is memory address and how to access?Example

What are pointers?

How to use pointers?Example !

What are the di"erences?

Example #Pointer ArithmeticExample $Example %


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OutlineArray o& pointerExample 'Example 7

Pointer to pointerExample (

Callin) &unction *y re&erence

Pass ar)uments *y re&erence

Example +Call,*y,-alue -s Call,*y,re&erence

???


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Introduction.ome C pro)rammin) tas/s are per&ormed

more easily with pointers0

Other tas/s cannot *e per&ormed withoutusin) pointers0

.uch as dynamic memory allocation0


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What is memory address and howto access?

E-ery -aria*le is a memory location0E-ery memory location has its address

de1ned0

Can *e accessed usin) ampersand 234operator0

5enotes as an address in memory0


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Example


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What are pointers?A -aria*le whose -alue is the address o&

another -aria*le0

6or example direct address o& the memorylocation0

8eneral &orm o& a pointer -aria*ledeclaration is

type *variable_name

type 9pointer:s *ase

type

-aria*le;name 9 nameo& the pointer -aria*le


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What are the pointers? The asteris/ < used to declare a pointer0.ame asteris/ that use &or multiplication0

Howe-er= in this statement the asteris/ is*ein) used to desi)nate a -aria*le as apointer0

6ollowin) are the -alid pointer declaration


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How to use pointers?.tep 5e1ne a pointer -aria*le0.tep ! Assi)n the address o& a -aria*le to

a pointer0

.tep # Access the -alue at the addressa-aila*le in the pointer -aria*le0


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Example !


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What are the di"erence?>-aria*le;num*er re&er to the -alue o& the

-aria*le0

>3-aria*le;num*er re&er to the addressthat contains -alue o& the -aria*le0

>-aria*le;pointer re&er to the address o&pointer0


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Example #


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Pointer ArithmeticArithmetic operation can *e per&ormed to

the pointer0

6or example pointer++;

A&ter a*o-e operation= thepointer

willpoint to the location @@$0

ecause each time pointer incremented= itwill point to the next inte)er location0

Bext inte)er location is $ *ytes next to thecurrent location0

5ecrementin) a pointer also can *e done0


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Example $ Incrementin) a pointer


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Pointer ArithmeticPointer can *e compared *y usin)

relational operators 99= D= and 0

I& pointer1 and pointer! point to -aria*lesthat are related to each other= thenpointer1 and pointer2 can *emeanin)&ully compared0


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Example % Pointercomparison


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Array o& Pointer There may *e a situation when we want to

maintain an array which can store pointersto an inte)er character or any other datatype a-aila*le0


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Example ' Recap o& array


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Example 7 Array o& inte)erpointer


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Pointer to pointerA pointer to a pointer is a &orm o& multiple

indirection or a chain o& pointers0

Bormally= pointer contains the address o&-aria*le0

Pointer to pointer contains the address o&the second pointer0

5eclaration int


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Example (


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Callin) &unctions *yre&erenceCall *y re&erence with pointer ar)umentsPasses address o& ar)ument usin) F&:

operator0Allows you to chan)e actual location in

memory0Arrays are not passed with F3: *ecause the

array name is already a pointer0

F


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Passin) ar)uments to &unction *yre&erence

Two ways to pass ar)uments to a &unctionCall,*y,-alueCall,*y,re&erence

Call,*y,-alue is normal pass ar)uments0

Howe-er= you can pass usin) pointer 2Call,*y,re&erence40

This is accomplished *y applyin) the

address operator 2&4 to the -aria*le0


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Example +


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Pass,*y,-alue -s pass,*y,re&erence

Passin) ar)ument *y -alue Passin) ar)ument *y re&erence

,usin) ordinary -aria*le ,usin) pointer -aria*le

,usin) re)ular -aria*le to pass -alue , usin) pointer to pass -alue

,uses more memory space ,sa-e some memory space

,copy o& actual -aria*leparameter ispassed to the &unction

,memory address o& the-aria*leparameter is passed to the&unction

,any modi1cation to -aria*leparameterinside &unction will not a"ect actual-alue

,any modi1cation to -aria*leparameterinside &unction will a"ect actual -alue


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POP,GIJ

int -alue= -alue!=

Chapter 7 Pointers unimap

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