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... strStates(1) read 'strStates sub one' Individual variables referred ... Use to code a loop containing instructions to be processed for each element in a group ... – PowerPoint PPT presentation

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Title: Click to edit Master title


1
1
2
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

3
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

4
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

5
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

6
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

7
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

8
One-Dimensional Arrays (continued)
9
HOW TO
10
Storing Data in a One-Dimensional Array
11
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

12
Displaying the Contents of a One-Dimensional Array
13
Displaying the Contents of a One-Dimensional
Array (continued)
14
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

15
HOW TO
16
Using the Subscript to Access an Element in a
One-Dimensional Array
Display salary amount corresponding to code
entered by user
17
Searching a One-Dimensional Array
  • Determine number of salespeople selling above a
    certain amount

18
Calculating the Average Amount Stored in a
One-Dimensional Numeric Array
  • Calculate and display average test score earned
    by students on final exam

19
Determining the Highest Value Stored in a
One-Dimensional Array
  • Display highest amount earned in a week

20
Updating the Values Stored in a One-Dimensional
Array
  • Procedure allows manager to increase price of
    each item and display items new price

21
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

22
Sorting the Data Stored in a One-Dimensional
Array (continued)
  • btnSortAscending_Click procedure sorts intNumbers
    array into ascending order

23
Sorting the Data Stored in a One-Dimensional
Array (continued)
24
Sorting the Data Stored in a One-Dimensional
Array (continued)
  • Method sorts array in descending order and
    displays the results

25
Sorting the Data Stored in a One-Dimensional
Array (continued)
26
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

27
Using a Module-Level One-Dimensional Array
(continued)
28
Using a Module-Level One-Dimensional Array
(continued)
29
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

30
Parallel One-Dimensional Arrays (continued)
31
Parallel One-Dimensional Arrays (continued)
32
Parallel One-Dimensional Arrays (continued)
33
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)

34
Two-Dimensional Arrays (continued)
35
HOW TO
36
Storing Data in a Two-Dimensional Array
37
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

39
TOE Chart
40
User Interface
41
Objects, Properties, and Settings
42
Objects, Properties, and Settings (continued)
43
Tab Order
44
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

45
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

46
Code
47
Code (continued)
48
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

49
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)

50
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

51
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

52
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

53
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
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