9. arrays strings

8/17/2019 9. Arrays Strings

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Lecture 6 of C LanguageLecture 6 of C LanguageArrays


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Introducing ArraysIntroducing Arrays

Array are collection of elements of samedata type.

All elements are consecutively inmemory.

Each element can be individually

referenced by adding an index to aunique name.

Uses:

Arrays are useful when we store relateddata items.


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Introducing ArraysIntroducing Arrays

Examples#

List of mar$s of students

List of grades of studentsList of employees in an organi%ation

List of names of students


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Declaration ofDeclaration of an Arrayan Array

type Array_name[size];&ere si%e indicates the maximum number

of elements.

'he subscript value start from 0 to size-1.

Example#

int number()*+, -oat number()*+,

char grade()*+,


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Initialising an ArrayInitialising an Array

An array is initiali%ed after it is declared. 'he following array can hold mar$s of ve

sub/ects#

int mar$s(0+,

An array can be initiali%ed in following ways:

First approach: 'he value of each element islisted within two curly brac$ets 1 2 and a comma

345is used to separate one element from another.

E! mar"s [#] $ %##& '0& (0& )0& *0+


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,econ- approach:elements of array can be initilised one at a time.

Ex. mar$(*+ 00,

mar$()+ 6*,

mar$(7+ 8*,

mar$(9+ :*,

mar$(8+ ;*,

!ote# In an array index of rst element is considered

as %ero. 'herefore in an array of n elements rst index is 0

and last index is n./.


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void main35

1int A[/0]&i4/4temp,

printf3?Enter )* numbers@5,

for3i*, i=)*, i5 scanf3?Bd@4A(i+5,


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Di%e of an ArrayDi%e of an Array

nce an array is declared4 its si%e isxed.

After that it can not changed.

Ex. int A()*+,

Can store only )* elements 3A(*+ toA(;+5.


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Feclaring4 creating and initilising insingle step#

int mar$s(0+10*4 6*4 8*4 :*4 ;*2


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Gultidimensional ArrayGultidimensional Array

'he type of array that we have discussed tillnow is single -imensional array as it hasonly single index.

wo -imensional arrays also calle- as matri!wo -imensional arrays loo"s li"e this:

Row 0

Row 1

Row 2

Row 3

Column 0 Column 1 Column 2 Column 3


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Declaration: 12lti-imensionalDeclaration: 12lti-imensional

ArrayArraytype array_name[row_size][col2mn_size];

row_size H>!umber of rows in matrix

col2mn_size H> !umber of columns in matrix

E: e can declare an array to store )**students mar$s for ve sub/ects.

int mar"s[/00][#];Eamples:

int n2m3er[(][4]; 56 /7 elements 65

8oat n2m3er[4][7]; 56 ' elements 65

char name[/0][70]; 56 700 chars 65


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Initiali%ation of a 7JF ArrayInitiali%ation of a 7JF Array

int a[2][3]={1,2,3,4,5,6};

int a[2][3]={{1,2,3}, {4,5,6}};

int a[][3]={{1,2,3}, {4,5,6}}

int a[2][3]={0}

Following initializations are not allowed

int a[3][]={2,4,6,8,10,12};

int a[][]={2,4,6,8,10,12};

!ote# If the rst brac$et pair is empty4 thencompiler ta$e the si%e from the number of innerbrace pairs


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ExampleExample9incl2-e st-io!h

9-e


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Gemory Gap for 7JFGemory Gap for 7JF

ArraysArraysKept in memory as a linear sequence of variables. 'wo methods for storingJ◦ Gow ma@or

◦ Hol2mn ma@or

Example#int a[4][4];

Gow ma@or storage:

a[0][0]& a[0][/]& a[0][7]& a[/][0]& a[/][/]&a[/][7]& a[7][0]& a[7][/]& a[7][7]

Hol2mn ma@or storage:

a[0][0]& a[/][0]& a[7][0]& a[0][/]& a[/][/]&a[7][/]& a[0][7]& a[/][7]& a[7][7]


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DtringsDtrings


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DtringsDtrings

• 'he way a group of integers can bestored in an integer array4 similarly agroup of characters can be stored in acharacter array. Character arrays aremany a time also called strings.

• A string is a oneJdimensional array ofcharacters terminated by a null 3 M*N 5.

• !ormally each character is stored in onebyte4 successive characters are storedin successive bytes.


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!ull Character!ull Character

'he terminating null 3M*N5 is important4because it is the only way to $nowwhere the string en-s. In fact4 a

string not terminated by a M*N is notreally a string4 but merely a collectionof characters.


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Feclaring stringsFeclaring strings

Char stringname(si%e+,

'he si%e determines the number of charactersin the string name.

Eample:

char monthname()7+, char address()**+,

'he si%e of the array should be one 3ytemore than the act2al space occ2pie- bythe string since the complier appends anull character at the end of the string.


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Initializing ,tringsInitializing ,trings

char month( +1/N4NaN4NnN4NuN4NaN4NrN4NyN 4NM*N2,

r

char month( +1@/anuary@2,

'hen the string month is initiali%ing to Panuary. 'his is perfectly valid but C o"ers aspecial way to initiali%e strings. 'he

above string can be initiali%ed charmonth)(+@Panuary@. 'he characters ofthe string are enclosed within a part ofdouble quotes.


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Dtring Initiali%ation#Dtring Initiali%ation#

char str(;+ ?I li$e C@, same as

char str(;+1IN4 4NlN4iN4N$N4NeN4 4NCN4NM*N2,

Q. Is there any di"erence between followingInitiali%ationR

char str(+?I'G@,

char str(8+ ?I'G@,

Ans# Ses4 in second declaration there is no nullcharacter


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Gea-ing ,trings from the terminal:Gea-ing ,trings from the terminal:

• 'he function scanf with Bs formatspecication is needed to readthe character string from the terminal.

•

Eample:

•

char address()0+,scanf3?Bs@4address5,

Dcanf statement has a -raw 3ac" it /ust

terminates the statement as soon as it nds ablan$ space4 suppose if we typethe string New Jor" then only the string !ew will be read and since there is a blan$ spaceafter word NewC it will terminate the string.


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22

Arrays of DtringsArrays of DtringsDeclaration:

char name[#][40];

Tive strings each contains maximum thirty characters.

Initialization:char[#]

[/0]$%KneC&CwoC&ChreeC&CFo2rC&CFi=eC+;

Kther =ali- -eclarationschar[][]$%KneC&CwoC&ChreeC&CFo2rC&CFi=eC+;

char[#][]$%KneC&CwoC&ChreeC&CFo2rC&CFi=eC+;


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Copying DtringCopying Dtring

• we cannot assign one string to another directly.

For eample:

•

Dtring)@xy%@,Dtring7string),

Are not valid.

• 'o copy the chars in one string toanother string we may do so on acharacter to character 3asis.


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,tring operations >string!h?,tring operations >string!h?

• C library supports a large numberof string handling functions that can be usedfor string manipulations such as#

• Length 3number of characters in the string5.

• Concatenation 3adding two are more strings5• Comparing two strings. 3if equal or not5• Copy3copies one string over another5

• 'o do all the operations described here it isessential to include string.h library header le inthe program.


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strlen>? f2nction:strlen>? f2nction:

• 'his function counts and returns the numberof characters in a string. 'he length does not include anull character.

•

,ynta•

nstrlen3string5,here n is integer variable. hich receives the valueof length of the string.

Eample

lengthstrlen3?&ollywood@5,•

'he function will assign number of characters ; in thestring to a integer variable length.


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strcat>? f2nction:strcat>? f2nction:

• when you combine two strings4 you add the characters

of one string to the end of other string. 'his process iscalled concatenation. It ta$es the following form

strcat>string/&string7?

string) string7 are character arrays. hen thefunction strcat is executed string7 is appended tostring).

Eample

strcpy3string)4@deep@5,strcpy3string74@$amal@5,

strcat3string)4string75,

Trom the above program segment the value of string)

becomes deep$amal. 'he string at str7 remainsunchanged as $amal.


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strcmp f2nction:strcmp f2nction:• In C you cannot directly compare the value of 7 strings in a condition

li$e if3string)string75

Gost libraries however contain the strcmp35 function4 which ret2rns azero if 7 strings are equal4 or a non zero n2m3er if the strings arenot the same.

'he syntax of strcmp35 is given below#

•

,trcmp>string/&string7?

Eample:

•

strcmp3?!ewyor$@4@!ewyor$@5 will return %ero because 7 strings are

equal.

strcmp3?their@4@there@5 will return a ; which is the numeric di"erencebetween ADCII iN and ADCII NrN.

strcmp3?'he@4 ?the@5 will return 97 which is the numeric di"erence

between ADCII ?'@ ADCII ?t@.


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strcpy>? f2nction:strcpy>? f2nction:• C does not allow you to assign the characters to a

string directly as in the statement name@Uobert@,Instead use the strcpy function found in mostcompilers.

• syntax

strcpy>string/&string7?;•Dtrcpy function assigns the contents of string7 tostring). string7 may be a character array variable ora string constant.

•

strcpy3!ame4@Uobert@5,•

In the above example Uobert is assigned to thestring called name.

9. arrays strings

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