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Objectives

• Declare and initialize a one-dimensional array
• Store data in a one-dimensional array
• Display the contents of a one-dimensional array
• Code a loop using the For EachNext statement
• Access an element in a one-dimensional array

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Objectives (continued)

• Search a one-dimensional array
• Compute the average of a one-dimensional arrays
  contents
• Find the highest entry in a one-dimensional array
• Update the contents of a one-dimensional array
• Sort a one-dimensional array

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Objectives (continued)

• Enter code in the forms Load event procedure
• Create and manipulate parallel one-dimensional
  arrays
• Create and initialize a two-dimensional array
• Store data in a two-dimensional array
• Search a two-dimensional array

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Using Arrays

• Simple variable
• Also called scalar variable
• Is unrelated to any other variable in memory
• Array
• A group of variables that have the same name and
  data type and are related in some way
• You can picture an array as a group of small
  adjacent boxes inside the computers memory

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One-Dimensional Arrays

• One-dimensional array
• Visualize as a column of variables
• Each variable is identified by a unique number
• Unique number is called subscript
• Subscript is placed inside parentheses
  immediately following array name
• Example strStates(1) read strStates sub one
• Individual variables referred to as elements

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One-Dimensional Arrays (continued)

• Declare using keywords Dim or Private
• highestSubscript argument in declaration used to
  specify the number of elements in the array
• number of array elements is 1 more than the
  value in highestSubscript argument

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One-Dimensional Arrays (continued)
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HOW TO
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Storing Data in a One-Dimensional Array
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Manipulating One-Dimensional Arrays

• Sample procedures will demonstrate how to perform
  tasks using a one-dimensional array
• Display contents of an array
• Access an array element using its subscript
• Search the array
• Calculate the average of the data stored in a
  numeric array
• Find the highest value stored in an array
• Update the array elements
• Sort the array elements

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Displaying the Contents of a One-Dimensional Array
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Displaying the Contents of a One-Dimensional
Array (continued)
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The For EachNext Statement

• Use to code a loop containing instructions to be
  processed for each element in a group
• Syntax template shown in next slide contains
  words element and group
• element
• Declare a variable of the same data type as the
  elements of the array and place this variable in
  the element position of the template
• group
• The variable name of the array

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HOW TO
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Using the Subscript to Access an Element in a
One-Dimensional Array
Display salary amount corresponding to code
entered by user
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Searching a One-Dimensional Array

• Determine number of salespeople selling above a
  certain amount

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Calculating the Average Amount Stored in a
One-Dimensional Numeric Array

• Calculate and display average test score earned
  by students on final exam

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Determining the Highest Value Stored in a
One-Dimensional Array

• Display highest amount earned in a week

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Updating the Values Stored in a One-Dimensional
Array

• Procedure allows manager to increase price of
  each item and display items new price

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Sorting the Data Stored in a One-Dimensional Array

• Array.Sort(arrayName) method
• Sorts the elements of a one-dimensional array in
  ascending order
• First element contains smallest value
• Last element contains largest value
• To sort in descending order
• First sort in ascending order
• Then use Array.Reverse(arrayname) method to
  reverse the position of the elements in the array

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Sorting the Data Stored in a One-Dimensional
Array (continued)

• btnSortAscending_Click procedure sorts intNumbers
  array into ascending order

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Sorting the Data Stored in a One-Dimensional
Array (continued)
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Sorting the Data Stored in a One-Dimensional
Array (continued)

• Method sorts array in descending order and
  displays the results

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Sorting the Data Stored in a One-Dimensional
Array (continued)
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Using a Module-Level One-Dimensional Array

• Application displays names contained in a
  sequential access file, giving user choice of
  ascending or descending order of display
• First, declare array variable in the Forms
  general declarations section
• Then, fill array from data in file using code in
  the forms Load event procedure
• Load event occurs before the first time a form is
  displayed

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Using a Module-Level One-Dimensional Array
(continued)
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Using a Module-Level One-Dimensional Array
(continued)
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Parallel One-Dimensional Arrays

• Two or more one-dimensional arrays whose elements
  are related by their position (subscript)
• Called parallel because element at subscript 0 in
  first array corresponds to element at subscript 0
  in another array
• Example
• strID(0) corresponds to intPrice(0) and
• strID(1) corresponds to intPrice(1),
• and so on

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Parallel One-Dimensional Arrays (continued)
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Parallel One-Dimensional Arrays (continued)
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Parallel One-Dimensional Arrays (continued)
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Two-Dimensional Arrays

• Resemble a table in that variables are store in
  rows and columns
• Each element is identified by a unique
  combination of two subscripts
• The first subscript indicates the elements row
• The second subscript indicates the column
• Each subscript begins with 0
• The element in the first row and column has a
  subscript of (0,0)

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Two-Dimensional Arrays (continued)
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HOW TO
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Storing Data in a Two-Dimensional Array
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Searching a Two-Dimensional Array
38
Programming Example Perrytown Gift Shop
Application

• Application is to assist in employee weekly
  payroll process
• Calculates and displays the federal withholding
  tax (FWT)
• Gets and displays taxable wages
• Gets and displays marital status

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TOE Chart
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User Interface
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Objects, Properties, and Settings
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Objects, Properties, and Settings (continued)
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Tab Order
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Pseudocode

• btnExit Click event procedure
• close application
• btnCalc Click event procedure
• Include the following in a Try/Catch block
• remove any dollar signs and spaces from the
  txtTaxable control
• assign the taxable wages store in txtTaxable to
  a variable
• assign the marital status entered in txtStatus
  to a variable
• if marital status is not either M or S
• display an appropriate message
• else
• if marital status is M
• use the Married tax table, stored in an array
• else
• use the singles tax table, stored in an array

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Pseudocode (continued)

• end if
• end if
• Repeat while there are still rows in the tax
  table to search and taxable wages have not been
  found
• if taxable wages are less than or equal to value
  stored in the first column of the current row in
  tax table
• use information stored in 2nd, 3rd, and 4th
  columns in tax
• table to calculate the federal withholding tax
• indicate that the taxable wages were found by
  assigning the
• value True to blnFound variable
• else
• add 1 to the contents of the intRow variable to
  continue the search
• row in the tax table
• Display the federal withholding tax in the lblFwt
  control
• Use general Catch statement to handle and display
  any errors

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Code
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Code (continued)
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Summary

• Programmers use arrays to temporarily store
  related data in computers internal memory
• All variables in an array have the same name and
  data type
• Each element in a one-dimensional array is
  identified by a unique subscript
• Appears in parentheses after arrays name

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Summary (continued)

• Each element in a two-dimensional array is
  identified by a unique combination of two
  subscripts
• Row subscript
• Column subscript
• Subscripts appear in parentheses after the
  arrays name
• You list the row subscript first, followed by a
  comma and the column subscript
• The first subscript in a one-dimensional array is
  0 (zero)

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Summary (continued)

• First row subscript in a two-dimensional array is
  0 (zero)? likewise, the first column subscript
  also is 0 (zero)
• When declaring a one-dimensional array, provide
  either highest subscript or initial values
• When declaring a two-dimensional array, you
  provide either the highest row and column
  subscripts or the initial values

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Summary (continued)

• The number of elements in a one-dimensional array
  is one more than its highest subscript
• The number of rows in a two-dimensional array is
  one more than its highest row subscript?
  likewise, the number of columns is one more than
  its highest column subscript
• You usually use an assignment statement to store
  data in an array
• You refer to an element in a one-dimensional
  array using the arrays name followed by the
  elements subscript

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Summary (continued)

• You refer to an element in a two-dimensional
  array using the arrays name followed by the
  elements row and column subscripts, which are
  separated by a comma
• You can use the For EachNext statement to code a
  loop whose instructions you want processed for
  each element in an array
• You can use the Length property to determine the
  number of elements in the array

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Summary (continued)

• You use the Array.Sort method to sort the
  elements in a one-dimensional array
• You use the Array.Reverse method to reverse the
  order of the elements in an array
• The elements in parallel arrays are related by
  their subscript (or position) in each array