Arrays

1
Chapter 7

• Arrays

2
Outline and Objective

• Arrays in Visual Basic
• One- dimensional arrays
• Control arrays
• Two-dimensional arrays
• Searching
• Sorting

3
Array verses Simple Variable

• Simple variable is used to store a single value.
• Array variable is used to represent many values
  of the same type with one variable name.

4
Elements of an Array

• Array Name A valid variable name for the
  structure.
• Subscript or Index A value that refers to a
  particular array element.
• Element An individual data item within an array.

5
Array Declaration

• Syntax
• Dim arrayname ( 1 To n) As VarType

6
Examples of arrays

• Dim month ( 1 To 12) As String
• Dim score (1 To 30) As Single
• Dim students (1 To 30 ) As String

7
The Dim Statement

• Used when you need to define an array .
• The Dim statement sets up storage for array.
• A Dim statement must occur before the first
  reference to the array elements.

8
Initializing an Array

• Private Sub cmdWhoWon_Click()
• Dim teamName( 1To 5) As String
• Dim n As Integer
• ' Fill array with World Series Winners
• teamName(1) "Red Sox"
• teamName(2) "Giants"
• teamName(3) "White Sox"
• teamName(4) "Cubs"
• teamName(5) "Cubs"
• n Val(txtNumber.Text)
• picWinner.Print "The " teamName(n) " won
  World Series number" n
• End Sub

9
Array teamName()
Array Name

• teamName( 1 To 5) As String

Red Sox Giants White Sox Cubs Cubs
teamName(1)
Index
10
Initializing an Array by Reading from a File

• Dim student ( 1 To 30) As String
• Open STUDENTS.TXT For Input As 1
• For count 1 To 30
• Input 1, student ( count )
• Next count

11
Adding Rows in an Array

• Dim score( 1 To 30) As Single, student (1 To 30)
  As String
• Open STUDENT.TXT For Input As 1
• For count 1 To 30
• Input 1, student (count), score (count)
• Next count
• sum 0
• For count 1 To 30
• sum sum score(count)
• Next count
• average sum/30

12
Parallel Arrays

• Two arrays are referred to as parallel if
  subscripted variables having the same subscript
  are related.

13
Example of Parallel Arrays

• Dim nom ( 1 To 8) As String , score ( 1 To 8 ) As
  Integer
• Open SCORE.TXT For Input As 1
• For student 1 To 8
• Input 1, nom(student), score(student)
• Next student
• Close 1

14
Homework

• P. 323 2, 4, 6, 8, 10, 12, 14
• 30, turn in printout of code