Arrays Creating and Accessing Arrays Using Arrays Some

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Arrays • Creating and Accessing Arrays • Using Arrays • Some Additional Types of

Arrays • Creating and Accessing Arrays • Using Arrays • Some Additional Types of Arrays Chapter 7 1

Variable vs Array Chapter 7 2

Variable vs Array Chapter 7 2

Simple and Array Variables • A variable (or simple variable) is a name to

Simple and Array Variables • A variable (or simple variable) is a name to which Visual Basic can assign a single value. • An array variable is a collection of simple variables of the same type to which Visual Basic can efficiently assign a list of values. Chapter 7 3

Creating and Accessing Arrays • • • Declaring an Array Variable The Load Event

Creating and Accessing Arrays • • • Declaring an Array Variable The Load Event Procedure The Get. Upper. Bound Method Re. Dim Statement Using an Array as a Frequency Table Chapter 7 4

Example • Suppose that you want to evaluate the exam grades for 30 students

Example • Suppose that you want to evaluate the exam grades for 30 students and to display the names of the students whose scores are above average. Private Sub btn. Display_Click(. . . ) _ Handles btn. Display. Click Dim student 1 As String, score 1 As Double Dim student 2 As String, score 2 As Double Dim student 3 As String, score 3 As Double Chapter 7 5

It’s better when Using Arrays Upper bound of subscripts in the array Dim student(29)

It’s better when Using Arrays Upper bound of subscripts in the array Dim student(29) As String Dim score(29) As Double Array name Data type Chapter 7 6

Putting Values into an Array student(0) = "Tom Brown" subscript Read: "student sub zero

Putting Values into an Array student(0) = "Tom Brown" subscript Read: "student sub zero equals Tom Brown" Which means that the string "Tom Brown" is being stored at the first location in the array called student… because all arrays begin counting at 0. Chapter 7 7

Array Terminology • Dim array. Name(n) As Data. Type • 0 is the "lower

Array Terminology • Dim array. Name(n) As Data. Type • 0 is the "lower bound" of the array • n is the "upper bound" of the array – the last available subscript in this array • The number of elements, n + 1, is the size of the array Chapter 7 8

Upper Bound & Lower Bound This is Upper Bond This is Lower Bond Number

Upper Bound & Lower Bound This is Upper Bond This is Lower Bond Number of elements in this array is Chapter 7 9

Lab sheet 7. 1: Form mtxt. Number txt. Winner Chapter 7 10

Lab sheet 7. 1: Form mtxt. Number txt. Winner Chapter 7 10

Example – Initialize the Array in the Button Private Sub btn. Who. Won_Click(. .

Example – Initialize the Array in the Button Private Sub btn. Who. Won_Click(. . . ) _ Handles btn. Who. Won. Click Dim team. Name(3) As String Dim n As Integer 'Place Super Bowl Winners into the array team. Name(0) = "Packers" team. Name(1) = "Packers" team. Name(2) = "Jets" team. Name(3) = "Chiefs" 'Access array n = CInt(txt. Number. Text) txt. Winner. Text = team. Name(n - 1) End Sub Chapter 7 11

Lab sheet 7. 1: Early Super Bowls Chapter 7 12

Lab sheet 7. 1: Early Super Bowls Chapter 7 12

Load Event Procedure Occurs as the Form loads in memory Private Sub frm. Name_Load(.

Load Event Procedure Occurs as the Form loads in memory Private Sub frm. Name_Load(. . . ) _ Handles My. Base. Load The keyword My. Base refers to the form being loaded. This event procedure is a good place to assign values to an array. Chapter 7 13

Example- Initialize the Array in Form Load Dim team. Name(3) As String Private Sub

Example- Initialize the Array in Form Load Dim team. Name(3) As String Private Sub btn. Who. Won_Click(. . . ) Handles btn. Who. Won. Click Dim n As Integer n = CInt(txt. Number. Text) txt. Winner. Text = team. Name(n - 1) End Sub Private Sub frm. Bowl_Load(. . . ) Handles My. Base. Load 'Place Super Bowl Winners into the array team. Name(0) = "Packers" team. Name(1) = "Packers" team. Name(2) = "Jets" team. Name(3) = "Chiefs" End Sub Chapter 7 14

Initializing Arrays when they are being created • Arrays may be initialized when they

Initializing Arrays when they are being created • Arrays may be initialized when they are created: Dim array. Name() As var. Type = {value 0, _ value 1, value 2, . . . , value. N} • declares an array having upper bound N and assigns value 0 to array. Name(0), value 1 to array. Name(1), . . . , and value. N to array. Name(N). Chapter 7 15

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