CS1B – Introduction to Programming in C++Topic 4 - ArraysChapter 8 in the shrinkwrapChapter 9 in MalikCS1B – Saddleback CollegeWhy do we need Arrays?int main (){int item0, item1,item2;int sum;cout << “Enter 3 integers”;cin>> item0 >> item1>> item2;What do we do if we have tostore more than 1 piece of information of the same type?We declare different variables.cin>> item0 >> item1>> item2;sum = item0 + item1 + item2;cout << “The sum of the numbers = “ << sum <<endl;cout << “the numbers in reverse order are “;cout << item2 <<“ “ << item1 <<“ “<< item0 << endl;return 0;}2 of 34 Topic 4 - ch 8 - ArraysCS1B – Saddleback CollegeWhat are arrays? A collection of data of the same type– A special group of variables Arrays can hold – many pieces of data – all have the same data type and name, –but different values. –but different values.  “Aggregate” data type– Means “grouping” Used for lists of like items– Test scores, temperatures, names, etc.– Avoids declaring multiple simple variables– Can manipulate "list" as one entity3 of 34 Topic 4 - ch 8 - ArraysCS1B – Saddleback CollegeSimple & Composite data types Simple Data Types– Data types that store only one piece of information– What we have been using thus far– Int, float double, char, long Structured / Composite Data types– Each data item is a collection of other data items4 of 34 Topic 4 - ch 8 - ArraysCS1B – Saddleback CollegeDeclaring an ArraySyntax:dataType arrayName[number_of_elements]; Declaring an array allocates the memory for the array Exampleint score[5]; // declares an array of 5 integers named scoreThe number of elements can be…– a literal (e.g. 5)int score[5]– Or a named constantconst int NUMBER_OF_TESTS = 5;int score[NUMBER_OF_TESTS];5 of 34Topic 4 - ch 8 - ArraysCS1B – Saddleback CollegeElements and Indexes Each individual item in an array is called an element– Each element has an index value associated with it An index is a number which indicates which value we are referring to Example:score[0] the first element in our arrayIndexscore[0] the first element in our array The first element is ALWAYS zero So if we have 5 elements our index values would be 0,1,2,3,4or score[0], score[1], score [2], score[3], score[4] Note: The brackets specify the size in the declaration and the subscript or index anywhere else6 of 34 Topic 4 - ch 8 - ArraysCS1B – Saddleback CollegeMemory and Arraysintscore[5];score[0];score[1];4 bytesscore[2];0,1,2,3,4 are in boundsin boundsin boundsin bounds7of 34 Topic 4 - ch 8 - Arraysintscore[5];score[1];score[5];First element always has an index of 0score[4];score[2];score[3];score [5] will not producea compile-time errorIt will produce a run-time error.0,1,2,3,4 are in boundsin boundsin boundsin boundsall other values are out of boundsout of boundsout of boundsout of boundsCS1B – Saddleback CollegeIndexesAn index can be anything that evaluates to an integer– A literal• e.g. score[5]– A variable or a constant•e.g. score[i]•e.g. score[i]– An expression• e.g. score[2 * i - j]8 of 34 Topic 4 - ch 8 - ArraysCS1B – Saddleback CollegeInitializing Arrays Simple variables can be initialized at declaration:int price = 0; // 0 is initial value of after declarationor equivalently in the codeint price;price = 0;Arrays can be initialized at declaration as well:This is not consideredgood style do not do this in this class pleaseArrays can be initialized at declaration as well:int item[3] = {2, 12, 1};or equivalently in the code :int item[3];item[0] = 2;item[1] = 12;item[2] = 1;9 of 34 Topic 4 - ch 8 - Arrays5-99CS1B – Saddleback CollegeInitializing Arrays (2) If you have more elements than values in the list then the extras at the end default to zeroint item[5]={2,12,1};  int item [5] = {2,12,1,0,0};  You can also initialize all the elements to 0 using this methodint item[5]={0}This is not recommended!This is okay!This is okay! If you have more values than elements specified then you will get a compiler errorint item[5]={2,12,1,2,9,5}; compiler error If you don’t specify the number of elements it will default to the number of values in the listint item[]={2,12,1,2,9,5}; children will default to 6 elements10 of 34 Topic 4 - ch 8 - ArraysThis is not recommended!This is okay!CS1B – Saddleback CollegeInitializing using a FOR loop#include <iostream>int main(){float gpa[5]; // an array holding 5 grade point averages – INP.& OUT.// load the array from the keyboardfor(int i= 0; i< 5; i++){cout << "Enter the gpa for student " << i+ 1 << ": ";cin>> gpa[i];This loopinitializes cin>> gpa[i];}// output the contents of the arraycout << "\n\nStudent Grade Point Averages\n";for(int i= 0; i< 5; i++){cout << "\nGPA for student " << i+ 1 <<": " << gpa[i];}return 0;}11 of 34 Topic 4 - ch 8 - ArraysNOTE: For Loops are very useful when you need to access every element in an array.This loopoutputs the arrayinitializes the arrayCS1B – Saddleback CollegeExampleint item[3];int sum;sum=0;for (int i= 0; i< 3 ; i++){cout << “Enter an integer: ”;cin>> item[i];Do a desk check with Inputs 5, 10, 15indexindexindexindex sum sum sum sum indindindindOutputOutputOutputOutputitemitemitemitem0 1 2cin>> item[i];sum = sum + item[i];}cout << “The sum of the numbers = “ << sum << endl;cout << “The numbers in reverse are: “;for (int i= 2 ; i > -1 ; i-- ){cout << item[i] << “, ”;}12 of 34What if we want to have 10 items? What changes will we have to make?CS1B – Saddleback CollegeDefining a Constant as Array Size Always use defined/named constant forarray size Example:const intAR_SIZE = 5;int score[AR_SIZE];Note that it must be declaredas an integer!– NOTE: Can’t do this with a variable Improves readability Improves versatility Improves maintainability13 of 36 Topic 4 - ch 8 - ArraysThe number of elementsmust be known at compile timeUsing a constant is considered a best practiceCS1B – Saddleback Collegeconst int AR_SIZE =10;int item[AR_SIZE];int sum;sum=0;for (int i = 0 ; i < AR_SIZE; i++){cout << “Enter an integer: ”;cin>> item[i];Instead of all those changes we can use a constant and just change the constant.Works well if theycin>> item[i];sum= sum + item[i];}cout << “The sum of the numbers = “ << sum <<endl;cout << “The numbers in reverse order are: “;for (int i = AR_SIZE-1; ind > -1 ; ind--){cout <<