1. © 2012 EMC Publishing, LLC Slide 1 Chapter 8 Arrays  Can store many of the same type of data together.  Allows a collection of related values to be stored together with a single descriptive name.  A composite data type: a collection of elements  Each item is called an element and each element has an index value. The friends array has 5 elements:

2. © 2012 EMC Publishing, LLC Slide 2 Chapter 8 Declaring and Initializing Arrays  Declare and initialize with default values: Dim ages(4) As Integer'5 elements each 0  Declare and initialize with specific values: Dim ages() As String = {4, 10, 6, 22, 13};  Type inference can be used to determine the array type: Dim stuNames() = {"Mia", "Eli", "Eva", "Rose", "Wu"}

3. © 2012 EMC Publishing, LLC Slide 3 Chapter 8 Accessing Array Elements  An array element is accessed by including its index in parentheses after the array name: Me.lblAge.Text = ages(3)'age 22  An array element is changed through assignment: friends(2) = "Sunshine"

4. © 2012 EMC Publishing, LLC Slide 4 Chapter 8 Traversing an Array  The Length property returns the number of elements in an array: numElements = ages.Length'5  A For…Next loop is one way to traverse an array: For ageIndex As Integer = 0 To ages.Length – 1 ages(ageIndex) = InputBox("Enter age:") Next ageIndex

5. © 2012 EMC Publishing, LLC Slide 5 Chapter 8 Array As Parameters  A procedure declaration can include array parameters: Function SumOfValues (ByRef numArray() As Integer) As Integer An array should be declared ByRef so that the actual array is passed instead of requiring a copy to be made.  A procedure declaration can include an array element: Sub DisplayElement (ByVal number As Integer, ByRef lblLabel As Label) Passing just an element passes a copy of the value, preventing the element in the array from being changed.

6. © 2012 EMC Publishing, LLC Slide 6 Chapter 8 Arrays with Meaningful Indexes  Use the index value of an array element for determining the storage location of a value.  Simplifies storage and retrieval of data.

7. © 2012 EMC Publishing, LLC Slide 7 Chapter 8 Linear Search  Simplest searching algorithm.  Checks each element of an array, one after the other, until a specified value has been found or until the entire array has been checked.

8. © 2012 EMC Publishing, LLC Slide 8 Chapter 8 Dynamic Array  Varies in size during run time.  Used in situations where the size of an array may need to grow or shrink or when the array size is unknown at the start of the program.  ReDim is used to change an array's size: Dim ages(-1) As Integer'0 elements ReDim ages(4)'5 elements  ReDim can be executed over and over but all the values in the array are lost. To keep existing values use ReDim Preserve.

9. © 2012 EMC Publishing, LLC Slide 9 Chapter 8 Two-Dimensional Arrays  Represents data that corresponds to a grid  An element is referred to by its row and column. The TTTBoard(0, 2) element stores an X:

10. © 2012 EMC Publishing, LLC Slide 10 Chapter 8 Two-Dimensional Arrays  Declaration includes the index of the last element of each dimension separated by a comma : Dim TTTBoard(2, 2) As Char ‘9 elements  The Length property returns the total number of elements, 9 in the example above  The number of rows is determined with a statement similar to: arrayName.GetLength(0)  The number of columns is determined with a statement similar to: arrayName.GetLength(1)

11. Chapter 8 Two-Dimensional Arrays  Nested For…Next loops are often used to access the elements of a two-dimensional array.  A ReDim statement can be used to change the size of individual dimensions, but the number of dimensions cannot be changed once declared  Two-dimensioned array parameters should be declared ByRef with the array name followed by an empty set of parameters that includes a comma indicating 2 dimensions © 2012 EMC Publishing, LLC Slide 11

12. © 2012 EMC Publishing, LLC Slide 12 Chapter 8 Structures  A composite data type that groups related variables.  Members can be different data types.  Structure declarations are similar to: Structure ElementaryStudent Dim name As String Dim age As Integer Dim grade As Integer End Structure  Structures must be declared outside of any procedure and it is done usually at the beginning of a program  A structure variable can appear anywhere in the program

13. © 2012 EMC Publishing, LLC Slide 13 Chapter 8 Structure Arrays  Members are accessed with a dot (.): Dim newStu As ElementaryStudent newStu.age = 10 newStu.grade = 4  An array of structures can be used to store related information for a group of elements.  Members are accessed with a dot (.): Dim stus(50) As ElementaryStudent stus(3).age = 10 stus(3).grade = 4  Procedures can include structure parameters either ByRef or ByVal

14. © 2012 EMC Publishing, LLC Slide 14 Chapter 8 Enumerated Types  Defines a related set of named constants.  Enumerated type declarations are similar to: Enum Level Freshman Sophomore Junior Senior End Enum  A variable declared as an enumerated type is limited to storing the values defined in the enumeration.

15. © 2012 EMC Publishing, LLC Slide 15 Chapter 8 Arrays of Objects  Can store a reference to a set of control class objects.  Declared with the appropriate control class data type. For example, Button, Label, or PictureBox.  An array of control class objects can simplify code that sets the same property for multiple objects of the same type.