15 Arrays.pptx - Topic 15 Arrays 1 Displaying a Report 2 Problem We want to process 10 test scores and display a report A sample report is as follows

# 15 Arrays.pptx - Topic 15 Arrays 1 Displaying a Report 2...

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Topic 15 Arrays 1
Displaying a Report Problem: We want to process 10 test scores and display a report. A sample report is as follows: Score Grade 63 C 92 A 84 A . . . . . . 77 B 2
Displaying a Report Suppose we do it using this method: cout << "Score\tGrade\n:"; for(int i = 1; i <= 10; i++) { cout << "Enter test score " << i << ": "; cin >> score; if(score >= 80) . . . cout << score << "\t" << grade << endl; } 3
Displaying a Report The input/output for this program will be as follows: Enter test score 1: 63 63 C Enter test score 2: 92 92 A . . . This method cannot be used to display the report in the format we want. 4
Displaying a Report The program must read and store all the test scores, then process them and display the report. We should use 10 variables as follows: 5
Displaying a Report We read all the test scores and store them in the 1 0 variables. We cannot use a loop now. We must use cin object 1 0 times. cout << "Enter test score 1: "; cin >> score0 ; cout << "Enter test score 2: "; cin >> score1 ; . . . . cout << "Enter test score 10: "; cin >> score9 ; 6
Displaying a Report After we get all the test scores, we process them and display the score and the grade. We have to repeat the same actions 1 0 times. if( score0 >= 80) . . . cout << score0 << "\t" << grade << endl; if( score1 >= 80) . . . cout << score1 << "\t" << grade << endl; . . . . 7
Displaying a Report Now the input/output will be as follows: Enter test score 1: 63 Enter test score 2: 92 . . . Enter test score 10: 77 Score Grade 63 C 92 A . . . 77 B 8
Array ConceptBut what if we have many test scores, say 50? We cannot use this method!A better way is to use an array.An arrayis a collection of elementsthe same data type.An array has a name and a size. of 9
Array Concept Example: Array with 1 0 elements to store some data values. Array name – scores Array size – 1 0 Array name Array with 10 elements 10
Declaring an ArrayAn array must be declared before it can be used.General format for array declaration:element_type array_name[ array_size ]; Example:int scores[10];array namearray size 11
Declaring an Array int scores[10]; char name[10]; Array to store 10 integers Array to store 10 characters ( not a string ) 12 [9]
Declaring an Array double gpa[40]; Note: All the elements are the same data type. Array to store 40 floating point numbers 13
Accessing Elements in Arrays The elements in the array are arranged in a sequence. We can refer to the elements as the first element, the second element, and so forth until we get to the last element. 1 st element 10 th element 2nd element . . . . 14
Accessing Elements Each element in the array has an index . The indexes are written in brackets ([ ]). The first element has index 0. The last element has index ( array_size - 1 ). inde x 15
1 st element 10 th element 2nd element . . . . inde x Last element index is 9 First element index is 0 16
Accessing Elements in Arrays We use the index to refer to an element in the array. Example: if we have an array declaration as follows: int scores[ 1 0]; Then we can use the indexes as follows: scores[0] – refers to the 1 st element.