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1. Programming Fundamentals
Lecture 9

2. 2
Objectives
Inthischapter,youwill:
•Learnaboutarrays
•Explorehowtodeclareandmanipulatedata
intoarrays
•Understandthemeaningof“arrayindexout
ofbounds”
•Discoverhowtopassanarrayasa
parametertoafunction

3. 3
Introduction
•Beforeformallydefininganarray,letus
considerthefollowingproblem.
•WewanttowriteaC++programthatreads
fivenumbers,findstheirsum,andprintsthe
numbersinreverseorder.

4. 4
Introduction (continued)

5. 5
Introduction (continued)
•Thisprogramworksfine.However,ifyou
needtoread100(ormore)numbersandprint
theminreverseorder,youwouldhaveto
declare100variablesandwritemanycin
andcoutstatements.Thus,forlarge
amountsofdata,thistypeofprogramisnot
desirable.
•Thedatastructurethatletsyoudoallofthese
thingsinC++iscalledanarray.

6. 6
Arrays
•Array:isacollectionoffixednumberof
componentsallofthesamedatatype
•Aone-dimensionalarrayisanarrayinwhich
thecomponentsarearrangedinalistform
•Syntaxfordeclaringaone-dimensionalarray:
intExpisapositiveintegerandspecifiesthe
numberofcomponentsinthearray.

7. 7
Arrays (continued)

8. 8
Arrays (continued)

9. 9
Accessing Array Components
•Generalsyntax:
WhereindexExp,calledanindex
•Indexvaluespecifiesthepositionofthe
componentinthearray
•[]isthearraysubscriptingoperator
•Thearrayindexalwaysstartsat0

10. 10
Accessing Array Components
(continued)
•Considerthefollowingstatement:
intlist[10];
•Thisstatementdeclaresanarrayof10
components.
•Inotherwords,wehavedeclared10
variables

11. 11
Accessing Array Components
(continued)
•Theassignmentstatement:
list[5]=34;
stores34inlist[5],whichisthesixth
componentofthearray
•Supposeiisanintvariable.Then,
inti=3;
list[i]=63;

12. 12
Accessing Array Components
(continued)
•Next, consider the following statements:
list[3] = 10;
list[6] = 35;
list[5] = list[3] + list[6];

13. 13
Accessing Array Components
(continued)
Note: When you declare an array, its size must be known.

14. 14
Processing One-Dimensional
Arrays
•Somebasicoperationsperformedonaone-
dimensionalarrayare:
−Initializing
−Inputtingdata
−Outputtingdatastoredinanarray
−findingthesumandaverageoftheelements
ofthearray
−Findingthelargestand/orsmallestelement
•Easilyaccomplishedbyaloop

15. 15
Processing One-Dimensional
Arrays (continued)
•Considerthedeclaration
intlist[100];//arrayofsize100
•Usingforlooptoaccessarrayelements:
for(inti=0;i<100;i++)//Line1
cin>>list[i]; //Line2
•Thisstatementsread100numbersfromthe
keyboardandstorethenumbersinlist
•Similarly,youcanoutputthedatastoredin
thearray

16. 16
Practical Example
•Takeanarrayof5elementsandimplement
thefollowingoperations:
−Inputtingdata
−Outputtingdata
−Outputtingdatainreverseorder
−Findthesumofarrayelements
−Findtheaverageofarrayelements
−Findthelargestnumberinthearray
−Findthesmallestnumberinthearray

17. 17
Array Index Out of Bounds
•Ifwehavethestatements:
doublenum[10];
•Thecomponentnum[i]isvalidifi=0,1,
2,3,4,5,6,7,8,or9
•Otherwise,wesaytheindexisoutof
bounds
•InC++,thereisnoguardagainstindicesthat
areoutofbounds
•Itistheprogrammer’sresponsibilitytomake
surethattheindexiswithinbounds.

18. 18
Array Initialization During
Declaration
•Likeanyothersimplevariable,anarraycan
beinitializedwhileitisbeingdeclared.
•Example:
doublesales[]={12.25,32.50,16.90,23.85,
45.68};
•Inthiscase,itisnotnecessarytospecifythe
sizeofthearray
•Sizedeterminedbythenumberofvaluesin
thebraces

19. 19
Partial Initialization of Arrays
During Declaration
•Thestatement:
intlist[10]={0};
declareslisttobeanarrayof10
componentsandinitializesallofthemtozero
•Thestatement:
intlist[10]={8,5,12};
declareslisttobeanarrayof10
components,initializeslist[0]to8,
list[1]to5,list[2]to12andallother
componentsareinitializedto0

20. 20
Partial Initialization of Arrays
During Declaration (continued)
•Thestatement:
intlist[]={5,6,3};
declareslisttobeanarrayof3components
andinitializeslist[0]to5,list[1]to6,and
list[2]to3
•Thestatement:
intlist[25]={4,7};
declaresanarrayof25components;
initializeslist[0]to4andlist[1]to7;all
othercomponentsareinitializedto0

21. 21
Some Restrictions on Array
Processing
•Considerthefollowingstatements:
•C++doesnotallowaggregateoperationson
anarray:
•Solution:

22. 22
Some Restrictions on Array
Processing (continued)
•Thefollowingisillegaltoo:
•Solution:

23. 23
Address of an Array in Memory

24. 24
Searching an Array for a
Specific Item
•Practical Example?
Sample Run
Enter 10 integers:
2 56 34 25 73 46 89 10 5 16
Enter the number to be searched: 25
25 is found at position 3

25. Reading
Chapter 9:
Arrays and Strings