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Microsoft Visual Basic 2010 Arrays. Using a One-Dimensional Array Lesson A Objectives. After completing this lesson, you will be able to: Declare and initialize a one-dimensional array Assign data to a one-dimensional array Display the contents of a one-dimensional array

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using a one dimensional array lesson a objectives
Using a One-Dimensional ArrayLesson A Objectives

After completing this lesson, you will be able to:

  • Declare and initialize a one-dimensional array
  • Assign data to a one-dimensional array
  • Display the contents of a one-dimensional array
  • Access an element in a one-dimensional array
  • Search a one-dimensional array
  • Compute the average of a one-dimensional array’s contents
  • Find the highest entry in a one-dimensional array
  • Update the contents of a one-dimensional array
  • Sort a one-dimensional array
arrays
Arrays
  • A simple variable, also called a scalar variable, is one that is unrelated to any other variable in memory
    • An array is a group of variables that have the same name and data type and are related in some way
    • Although arrays in Visual Basic can have as many as 60 dimensions, the most commonly used arrays are one-dimensional and two-dimensional
    • Programmers use arrays to store related data in the internal memory of the computer
one dimensional arrays
One-Dimensional Arrays
  • A one-dimensional array is simply a row (or column) of variables
  • A two-dimensional array resembles a table in that it has rows and columns
  • Each element in an array is identified by a subscript, which Visual Basic assigns to the variable when the array is created
  • You refer to an array element by the array’s name followed by the element’s subscript
one dimensional array
One-Dimensional Array

strState(2)

strState(3)

strState(4)

strState(0)

strState(1)

strState(0)

strState(1)

strState(2)

strState(3)

strState(4)

declaring an array
Declaring an Array
  • Version 1

accessibilityarrayname(highestSubscript) As datatype

  • Version 2

accessibilityarrayname() As datatype = {initialValues}

  • These statements create and initialize the array variables in memory
  • accessibility is Dim, Public, or Private
declaring an array1
Declaring an array
  • Dim strCitys(3) As String
  • Private intNumbers(5) As Integer
  • Private udtItems(4) As ItemStruc
  • Private strStates() As String = {“Hawaii”, “Alaska”, “Maine”}
  • Dim intScores() As Integer = {75, 9, 23, 6}
storing data in a one dimensional array
Storing Data in a One-Dimensional Array
  • You can use a variety of ways to enter data into an array

strMonthArray(0) = “Jan”

strMonthArray(1) = “Feb”

strMonthArray(2) = “Mar”

strMonthArray(3) = “Apr”

strMonthArray(4) = “May”

strMonthArray(5) = “June”

assigning values to array elements
Assigning Values to Array Elements

For intNum = 1 to 6

intSquareArray(intNum - 1) = intNum * intNum

Next intNum

For intNum = 0 to 10

sngNum(intNum) = Val(InputBox(“Enter number”))

Next intNum

udtItems(0).sngPrice = udtItems(0).sngPrice * 1.1

one dimensional array1
One-Dimensional Array

Dim intX As Integer

Do While (intX <= 5 AndAlso Not EOF(1))

FileGet(1, udtItems(intX), intX + 1)

intX += 1

Loop

display the contents of a one dimensional array
Display the Contents of a One-Dimensional Array

Dim strMonths() As String = {“JAN”, “FEB”, “MAR”, “APR”, “MAY”, “JUN”, “JUL”, “AUG”, “SEP”, “OCT”, “NOV”, “DEC”}

Dim intX As Integer

For intX = 0 To strMonths.Length - 1

Me.MonthListBox.Items.Add(strMonths(intX))

Next intX

searching a one dimensional array
Searching a One-Dimensional Array

Dim intSales() As Integer = {45000, 35000, 25000, 60000, 23000}

Dim intX As Integer ‘keeps track of subscripts

Dim intCount As Integer ‘counter variable

Dim intSearchFor As Integer ‘number to search for

intSearchFor = Val(InputBox(“Enter sales to search for:”, _

“Sales”))

For intX = 0 To 4

If intSales(intX) > intSearchFor Then

intCount += 1

End If

Next intX

MessageBox.Show(“Count: ” & intCount, “Sales”, _

MessageBoxButtons.OK, MessageBoxIcon.Information)

calculating the average amount stored in a one dimensional numeric array
Calculating the Average Amount Stored in a One-Dimensional Numeric Array

Declare variables

Repeat for each score

add array score to intTotal variable

End repeat for intNum

Calculate the average by dividing intTotal by number of scores

Display the average

calculating the average amount stored in a one dimensional numeric array1
Calculating the Average Amount Stored in a One-Dimensional Numeric Array

Dim intScores() As Integer = {98, 100, 56, 74, 35}

Dim intX As Integer ‘keeps track of subscripts

Dim intTotal As Integer ‘accumulator variable

Dim sngAvg As Single ‘average score

For intX = 0 To intScores.Length - 1

intTotal += intScores(intX)

Next intX

sngAvg = intTotal / intScores.Length

MessageBox.Show(“Average: ” & sngAvg, “Average”, _

MessageBoxButtons.OK, MessageBoxIcon.Information)

determining the highest value stored in a one dimensional array
Determining the Highest ValueStored in a One-Dimensional Array

Declare variables

Assign first array value (zero) to intHigh variable

Initialize the intX variable to 1 (second subscript)

Repeat while intX is less than the number of elements in the array

If current array value > intHigh value then

assign current array value to intHigh

End If

End repeat for intNum

Display the highest value(stored in intHigh)

updating the values stored in a one dimensional array
Updating the Values Stored in a One-Dimensional Array

Declare variables

Prompt user for the value to add

Repeat for each price in the array

add value to current array value

display the contents of the current array element

End repeat

sorting the data stored in a one dimensional array
Sorting the Data Stored in a One-Dimensional Array

declare an Integer array named intNumbers

declare an Integer variable named intX

open the random access file named nums.data

repeat while intX is less than or equal to 5 and it is not the end of the nums.data file

read a number from the file and store it in the current array element

display the contents of the current array element in a message box

add 1 to the intX variable

end repeat

close the nums.data file

sort the intNumbers array in ascending order using the Array.Sort method

repeat for each element in the intNumbers array

display the contents of the current array element in a message box

end repeat

parallel arrays
Parallel Arrays
  • Arrays that are related by an element’s position (subscript)
  • Searching one array gives you the subscript for the other array

Dim strId() As String = {"BX35”, “CR20", “FE15”, “KW10”, “MM67”}

Dim intPrice() As Integer = {13, 10, 12, 24, 4}

Dim intX As Integer, strSearchFor As String

strSearchFor = UCase(IdTextBox.Text)

‘search the array

Do While intX < strId.Length AndAlso strSearchFor <> strId(intX)

intX += 1

Loop

an array of structures
An Array of Structures

Declare an ItemStruc array named udtPriceList

Declare variables intX and strSearchFor

Assign IDs and prices to the udtPriceList array

Assign the product ID entered in the IdTextBox control, converted to uppercase, to the strSearchFor variable

Repeat while intX is less than the list length and the value of strSearchFor variable is not equal to the value stored in the current array element’s strId field

Increment intX

End repeat

If the intX variable contains a number that is less than the lists length

display the appropriate price from the intPrice field in the array

Else

display the message “Product ID is not valid”

End if

two dimensional arrays
Two-Dimensional Arrays
  • A two-dimensional array resembles a table in that the variables are in rows and columns

strProducts(0, 0)

strProducts(0, 2)

strProducts(1, 2)

strProducts(2, 1)

multidimensional array properties
Multidimensional Array Properties
  • Length will tell you the total number of elements
    • intSales.Length will return 12
  • Use GetLength(dimension) to get the size of a particular dimension
    • intSales.GetLength(0) will return 6
    • intSales.GetLength(2) will return 2

For intRow = 0 To intSales.GetLength(0) - 1

For intCol = 0 To intSales.GetLength(1) - 1

intTotal = intTotal + intSales(intRow, intCol)

Next intCol

Next intRow