Ch 9 Using Arrays & File Handling

Explicite defined array

Dim MyVariable As DateType = x
Dim strName As String = "Rach"
Dim MyArray(5) As DataType
Dim strNames(2) As String

' Assign values
strNames(0) = "Rach"
strNames(1) = "Pam"
strNames(2) = "David"

An array contains multiple elements - array index begins at 0

Implicitly sized Array

Declare an array and populate with no definate value assigned
Dim strNames() As String = ("Baker", "Lopez", "Buck", "Chan", "Tirrell")
Dim intReservations() As Integer = {4, 5, 12, 2, 8}

Parallel Arrays
Dim intDinnerBookings(2) As Integer
Dim strNames(2) As String
' Loop to populate
' Data Table - strNames
' Bookings - intDinnerBookings

Dim ItemArray() As String = {"x", "y", "z"}
' 3 elements
Dim intCount As Integer
'Declared an Integer Variable

For intCount = 0 To ItemArray.Length -1
'Length = number of elements so .Length = -1
'Extract each item into the loop - start at 0
lstBox.Item.Add(ItemArray(intCount))

Next

Length returns the number of elements - not the upperbound

Index begins at zero
if the -1 is omitted from the .Length - it will loop 4 times instead of 3

= IndexOutOfRange Exception. A Try-Catch statement can catch this exception, but it is best to stay within the array boundaries of zero and the upper-bound array subscript.

Use loops to populate the array

Sorting Arrays
When applied - (default) the lowest value is placed in the 1st element in the array with an index of zero, next lowest is placed in the second element, etc

Array.Sort(ArrayName)
'Sort is a Function
Dim intAges() as Integer = {16, 64, 41, 8, 19, 81, 23}
Array.Sort(intAges)

Search Arrays
Sequential - searching each element with first name - not particularly efficient in large list
Binary - searches a sorted array for a value using a binary search algorithm = by repeatedly dividing the search interval in half = sort first - splits in half - searches on upper half of array to match the index - if match continues to split - no match - searches on lower half - them splits until found