07 bit 10303.pptx

7/21/2019 07 BIT 10303.pptx

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CHAP 7 : STRUCTURE AND POINTER

7/21/2019 07 BIT 10303.pptx


Chapter : STRUCTURE AND POINTER

7.1 Pointer and string 7.2 Str!tre and pointer 7." Nested str!tre 7.# Arra$ and str!tre

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%C% Progra&&ing 'ith Str!treRe!ords

Purpose of structuresCoding a structure template

Defining a new data typeFunctions which communicate

using structuresUse of structure pointersStructures and arraysAssi nin structures

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Lect 23 P. 4

Data Str!tres (str!t)

Arra$s re*ire that a++ e+e&ents ,e o- thesa&e data t$pe. an$ ti&es it is ne!essar$ togrop in-or&ation o- di/erent data t$pes. An

e0a&p+e is a &ateria+s +ist -or a prod!t. The+ist t$pi!a++$ in!+des a na&e -or ea!h ite& apart n&,er di&ensions eight and !ost.

C and C33 spport data str!tres that !an

store !o&,inations o- !hara!ter integer4oating point and en&erated t$pe data. The$ are !a++ed a structs.

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Lect 23 P. 5

Str!tres (str!t)

A struct is a deri5ed data t$pe !o&posed o-&e&,ers that are ea!h -nda&enta+ orderi5ed data t$pes.

A sing+e struct o+d store the data -or oneo,6e!t. An arra$ o- struct s o+d store thedata -or se5era+ o,6e!ts.

A struct !an ,e dened in se5era+ a$s asi++strated in the -o++oing e0a&p+es:

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Lect 23 P. 6

De!+aring Str!tres (str!t)

Reser5es Spa!e

str!t

&$9e0a&p+e

int +a,e+;

!har +etter;!harna&e<2=>;

? &$str!t ;

Does Not Reserve Space

struct my_example

{

int label;

char letter ;

char name[20];

} ;

/* The name "my_example" is

called a structure tag */

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Lect 23 P. 7

User Dened Data T$pes(t$pede-) The C +angage pro5ides a -a!i+it$ !a++ed typedef -or

!reating s$non$&s -or pre5ios+$ dened data t$pena&es. @or e0a&p+e the de!+aration:

t$pede- int ength;

&aBes the na&e Length a s$non$& (or a+ias) -or thedata t$pe int .

The data t$pe na&e Length !an no ,e sed inde!+arations in e0a!t+$ the sa&e a$ that the datat$pe int !an ,e sed:

ength a , +en ;

ength n&,ers<1=> ;

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Lect 23 P. 8

T$pede- Str!t

O-ten t ypedef is sed in !o&,ination ith struct tode!+are a s$non$& (or an a+ias) -or a str!tre:

t$pede- str!t FG Dene a str!tre GF

int +a,e+ ;

!har +etter;

!har na&e<2=> ;

? So&e9na&e ; FG The a+ias is So&e9na&e GF

So&e9na&e &$str!t ; FG Create a str!t 5aria,+e GF

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Lect 23 P. 9

A!!essing Str!t e&,ers

Indi5ida+ &e&,ers o- a struct 5aria,+e &a$ ,ea!!essed sing the str!tre &e&,er operator (thedot .):

&$str!t.+etter ;

Or i- a pointer to the struct has ,een de!+ared andinitia+ied

So&e9na&e G&$ptr J &$str!t ;

,$ sing the str!tre pointer operator (the KL): &$ptr KL +etter ;

hi!h !o+d a+so ,e ritten as:

(G&$ptr).+etter ;

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Lect 23 P. 10

Sa&p+e Progra& 'ithStr!tsFG This progra& i++strates !reating str!ts and then

de!+aring and sing str!t 5aria,+es. Note thatstr!t persona+ is an in!+ded data t$pe in str!tidentit$.GF

Min!+de stdio.hLstr!t persona+ FFCreate a str!t ,t dont reser5e spa!e.

+ong id;

4oat gpa;

? ;

str!t identit$ FFCreate a se!ond str!t that in!+des therst one.

!har na&e<"=>;

str!t persona+ person;

? ;

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Lect 23 P. 11

Sa&p+e Progra& 'ith Str!ts (!ont.)

int &ain ( )

str!t identit$ 6s J oe S&ith? Gptr J 6s ;

6s.person.id J 12"#Q7 ;

6s.person.gpa J ".# ;

print- (s +d -Vn 6s.na&e 6s.person.id

6s.person.gpa) ;

print- (s +d -Vn ptrKLna&e ptrKLperson.id

ptrKLperson.gpa) ;

?

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Prpose o- str!tres

Computing applications often

need data of different kinds to be

associated. A typical place wherethis occurs is in a record . For

example a database record for a particular student might contain

the student number full name

course!code and ear of entr .

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Re!ord de!+aration

str!t stdent

!har stdno<12>; !har na&e<Q=>;

!har !orse<7>; int start$ear;?;

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ore e0a&p+es

str!t !oord 4oat 0$; ?;str!t !o&p+e0 4oatrea+i&aginar$; ?;

"he data might ha#e different

types but does not ha#e to be ofdifferent types. Structures also

help with the naming of related

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A++o!ating &e&or$ tore!ords

"he abo#e declarations don%t create any space for data

storage but they pro#ide a template for data of the

appropriate types to be allocated. &et%s allocate somestorage to data #ariables'

str!t !oord origin !rsor;

FG 2 0K$ !oordinates !a++ed origin and!rsor GFstr!t stdent sdn9$ear2<Q=>;

FG arra$ -or Q= stdents GF

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Dening a ne data t$pe

(etter to ha#e one word e.g.COORD to declare the type of data

than ) words e.g. struct coord . "his

needs a typedef statement'

str!t !oord 4oat 0$; ?;t$pede- str!t !oord COORD;FG COORD no sa&e as str!t !oord GF

COORD origin !rsor;

FG de!+are 2 0K$ !oordinates !a++ed origin and!rsor GF

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Use o- the dot str!tre &e&,era!!ess operator

*embers x and y of origin and

cursor can now be accessed as

origin.x origin.y cursor.x and

cursor.y e.g.

origin.0J".Q;

origin.$J2.=;

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Ha5ing dened a ne datat$pe

!such as float and int . "his

simplification is useful as thename of the data type is going to

appear in many places within our

program e.g. for declaring types

of local data within functions or

function parameters.

,t may not seem the case but

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@n!tions hi!h !o&&ni!atesing str!tred para&eters

4oat distan!e(COORD a COORD ,)FG !a+!+ate distan!e ,eteen a and , GF

4oat 5erthori;FG J distan!e 5ert J $1 K $2 hori J 01 K 02 GF

horiJa.0 K ,.0; FG the horionta+ distan!e GF 5ertJa.$ K ,.$; FG the 5erti!a+ distan!e GF FG !a+!+ate as the h$potense o- a right ang+etriang+e GF Js*rt((horiGhori) 3 (5ertG5ert)); FG P$thagorstheore&: GF retrn ; FG G J 0G0 3 $G$

GF?

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@n!tions hi!h !o&&ni!atesing str!tred retrn 5a+esCOORD get!oord(5oid)

FG noteretrned t$pe is COORD GF

FG pro&pts -or and

retrns a !oordinate GF COORD te&p;

print-(Enter 0 and $!oordinates Vn); s!an-(-

-te&p.0te&p.$);

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A progra& sing distan!e andget!oord part 1

Min!+de stdio.hLMin!+de &ath.hL

FG needed to se s*rt() s*are root GF str!t !oord 4oat 0$; ?;

FG de!+are str!tre !oord as ha5ing 0 and $ &e&,ersGFt$pede- str!t !oord COORD;

FG COORD is no sa&e as str!t !oord GFCOORD origin !rsor;

FG de!+are 2 0K$ !oordinates !a++ed origin and !rsor GF

FG -n!tion protot$pes GF4oat distan!e(COORD a COORD ,);COORD get!oord(5oid);

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A progra& sing distan!e andget!oord part 2

int &ain(5oid) COORD origin !rsor; 4oat separation;

print-(enter detai+s -or origin:Vn); originJget!oord();print-(enter detai+s -or !rsor:Vn);

!rsorJget!oord();

separationJdistan!e(origin!rsor); print-(the distan!e ,eteen originand !rsor is -Vnseparation); retrn =;

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Use o- str!tre pointers*embers x and y of coordinates a

and b can also be accessed

through pointers to a and b so

that if pointer p stores the addressof a' p=&a; then

p->x

directl accesses member x of a

e! ara ons a o5e ere

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Rerite the a,o5e progra& singpointers

e! ara ons a o5e ereo- headers str!t !oord

and t$pede- COORD sa&eas ,e-ore so not repeatedGF4oat distan!e(COORD GaCOORD G,);

FG a and , are nopointers to COORD GF

5oid get!oord(COORD

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Str!tres and arra$s-a#ing indi#idual names for / coordinates is #ery

awkward. +e can declare the data as an array'

t$pede- str!t !oord 4oat 0$; ? COORD;COORD graph<1=>;

+e can then assign members of our structure array like

this'

graph<>.0 J 12.Q; graph<>.$ J 7."; FGassign 5a+es to tenth e+e&ent <> o- grapharra$ GF

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Or e !o+d inpt 5a+es into a++!oordinates sing a +oop

int i;-or(iJ=;i1=;i33) print-(Enter 0 5a+e -or !oordinatedVni31);

s!an-(-graph<i>.0); print-(Enter $ 5a+e -or !oordinatedVn

i31);s!an-(-graph<i>.$);

?

O i t t i t

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Or sing str!tre pointernotation

int i;-or(iJ=;i1=;i33)

print-(Enter 0 5a+e -or !oordinatedVni31);

s!an-(-(graph3i)KL0);FG KL has higher pre!eden!e than GF

print-(Enter $ 5a+e -or !oordinatedVni31);s!an-(-(graph3i)KL$);

?

A t t t i i

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A str!tre !ontaining anarra$

t$pede- str!t stdent !har na&e<"=>;

4oat &arB;? STUDENT;

STUDENT $o;print- (enter na&e and &arBVn);s!an- (s-$o.na&e$o.&arB);

FG $o.na&e is the address o- the na&e arra$ GFFG so no a&persand needed to get addressGFFG WUT $o.&arB is not an arra$ so needs GF

print- (he++o s $or &arB is -Vn$o.na&e$o.&arB);print- (The rst +etter o- $or na&e is !Vn$o.na&e<=>);

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Assigning str!tres

Unlike arrays structures can be copied as a complete entity

using a single assignment. "his sa#es time. So instead of

writing'

str!p$(te&p.na&e$o.na&e);FG se -n!tion str!p$ to !op$ a string GF

te&p.&arB J $o.&arB;FG !an assign &arB in one go GF

we can write'

te&pJ$o; FG !op$ str!tre in one go GF

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Pointer @nda&enta+s 'hen a 5aria,+e is dened

the !o&pi+er (+inBerF+oadera!ta++$) a++o!ates a rea+&e&or$ address -or the5aria,+e. int 0; i++ a++o!ate # ,$tes

in the &ain &e&or$ hi!hi++ ,e sed to store an integer5a+e.

'hen a 5a+e is assigned toa 5aria,+e the 5a+e isa!ta++$ p+a!ed to the&e&or$ that as a++o!ated.

0J"; i++ store integer " in

00000000

00000000

00000000

00000011

x

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Pointers 'hen the 5a+e o- a 5aria,+e is

sed the !ontents in the&e&or$ are sed. $J0; i++ read the !ontents

in the # ,$tes o- &e&or$ andthen assign it to 5aria,+e $.

0 !an get the address o- 0.(re-eren!ing operator )

The address !an ,e passed to a-n!tion:

s!an-(d 0); The address !an a+so ,e stored

in a 5aria,+e XX

00000000

00000000

00000000

00000011

x

y

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Pointers To de!+are a pointer 5aria,+e

t$pe G pointerna&e;

@or e0a&p+e: int G p1; p1 is a 5aria,+e that tends to point

to an integer (or p1 is a int pointer) !har Gp2;

nsigned int G p";

p1 J 0; FG Store the address in p1 GF s!an-(d p1); FG i.e. s!an-(d0); GF p2 J 0; FG 'i++ get arning &essage GF

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Initia+iing Pointers iBe other 5aria,+es a+a$s initia+ie

pointers ,e-ore sing the&YYY @or e0a&p+e:

int &ain()

int 0;int Gp;

p J 0;s!an-(dp); FG Corre!t GF

?

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Using Pointers Zo !an se pointers to a!!ess the 5a+es

o- other 5aria,+es i.e. the !ontents o- the&e&or$ -or other 5aria,+es.

To do this se the G operator

(dere-eren!ing operator). Depending on di/erent !onte0t G has

di/erent &eanings.

@or e0a&p+e:

int n &J" Gp;

pJ&;

nJGp;

print-(dVn n);

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An E0a&p+eint &J" nJ1== Gp;

pJ&;

print-(& is dVnGp);

&33;

print-(no & is dVnGp);

pJn;

print-(n is dVnGp);

GpJQ==; FG Gp is at the +e-t o- J GFprint-(no n is dVn n);

3

4

100

500

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int &ain() print-(Enter $or na&e ); s!an-(ssA.Na&e); print-(Enter $or ,a+an!e ); s!an-(+-sA.,a+an!e); print-(VnNa&e : s sA.Na&e); print-(+- sA.,a+an!e); get!h(); ?

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Pointer Arith&eti! (1)

int a< 1= > Gp;

p J a<2>;

Gp J 1=;

G(p31) J 1=;

print-(d G(p3"));

int a< 1= > Gp;

a<2> J 1=;

a<"> J 1=;

print-(d a<Q>);

a a[0] a[1] a[2] a[3] a[4] a[] a[!] a[] a[#] a[$]

p p%1 p%2 p%3 p%4 p% p%! p%

&hen a p'inter (ariable p'ints t' an array element) there is a n'ti'n ' adding 'r

subtracting an integer t'/r'm the p'inter+elements

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Pointer Arith&eti! (2) ore e0a&p+es:

int a<1=> Gp G*;

p J a<2>;

* J p 3 "; FG * points to a<Q> no GF

p J * [ 1; FG p points to a<#> no GFp33; FG p points to a<Q> no GF

pKK; FG p points to a<#> no GF

Gp J 12"; FG a<#> J 12" GF

G* J Gp; FG a<Q> J a<#> GF

* J p; FG * points to a<#> no GF

s!an-(d *) FG s!an-(d a<#>) GF

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Pointer Arith&eti! (") I- to pointers point to e+e&ents o- a

sa&e arra$ then there are notions o-s,tra!tion and !o&parisons ,eteen theto pointers.

int a<1=> Gp G* i;

p J a<2>;

* J a<Q>;

i J * K p; FG i is "GF

i J p K *; FG i is K" GFa<2> J a<Q> J =;

i J Gp K G*; FG i J a<2> [ a<Q> GF

p *; FG tre GF

p JJ *; FG -a+se GF

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Str!t

struct delcaration format

str!t tag str!treL

datat$pesL indentier1;

datat$pesL indentier2;

:

datat$pesL indentier";

?

struct sta/

char na&e<1Q>;int sta/9id;

float sa+ar$;char position<1=>;

?

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I++stration o- str!t storage

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E0a&p+e

1. 'rite a re!ord o- a na&e !onsists o- data: rstNa&e andse!ondNa&e.

2. 'rite a progra& seg&ent to a++o ser to enter the inpt -orea!h e+d o- the str!t in (1).

". 'rite a re!ord o- a detai+ !onsists o- data: position sta-Id and

sa+ar$.

#. 'rite a progra& seg&ent to a++o ser to enter the inpt -orea!h e+d o- the str!t (2).

Q. 'rite a re!ord o- a orBerIn-o sing str!t &e!hanis&. There!ord !onsists o- na&e and detai+ here:

i. the na&e !onsists o- the -o++oing data: rstNa&e and se!ndNa&e.

ii. the detai+ !onsists o- the -o++oing data: position sta-Idand sa+ar$.

. 'rite a progra& seg&ent to a++o ser to enter the inpt -orea!h e+d o- the str!t.

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Ne0t Chapter :

FILE

.1 The sage o- +e in Cprogra&&ing -or inpt and to

prod!e otpt or report

07 bit 10303.pptx

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