1. Programming with Microsoft Visual Basic 2005, Third Edition
Chapter 9: Arrays
Programming with Microsoft Visual Basic 2005, Third Edition

2. Using a One-Dimensional Array Lesson A 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 Each…Next statement
Access an element in a one-dimensional array
Programming with Microsoft Visual Basic 2005, Third Edition

3. Using a One-Dimensional Array Lesson A Objectives (continued)
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
Programming with Microsoft Visual Basic 2005, Third Edition

4. Previewing the Completed Application
Go to Run command on Windows Start menu
Browse to the VB2005\Chap09 folder
Open the Perrytown.exe file
Perrytown Gift Shop user interface appears
Programming with Microsoft Visual Basic 2005, Third Edition

5. Previewing the Completed Application (continued)
Figure 9-1: FWT for a married employee with taxable wages of $288.46
Programming with Microsoft Visual Basic 2005, Third Edition

6. Using Arrays Simple (scalar variable) Array Reasons to use arrays
One unrelated to any other variable in memory
Array
Group of variables
Group members have same name and data type
Reasons to use arrays
Simplifies process of coding an application
Increases run-time efficiency of a program
Programming with Microsoft Visual Basic 2005, Third Edition

7. One-Dimensional Arrays
Sequence of contiguous memory cells
Visualized as a column of variables
Subscript: integer identifying an array variable
Refer to array variable by array name and subscript
Example: states(0) is the first variable in states array
There are two ways to declare arrays
Programming with Microsoft Visual Basic 2005, Third Edition

8. One-Dimensional Arrays (continued)
Figure 9-2: Names of the variables in a one-dimensional array named states
Programming with Microsoft Visual Basic 2005, Third Edition

9. One-Dimensional Arrays (continued)
Figure 9-3: Syntax versions and examples of declaring a one-dimensional array
Programming with Microsoft Visual Basic 2005, Third Edition

10. One-Dimensional Arrays (continued)
Element: refers to an individual array variable
“Off by one” issue: first element has a subscript of 0
“Off by one” issue in Syntax-Version 1
Size of new array exceeds highestSubscript by 1
Populating an array: assigning initial values
“Off by one” issue in Syntax-Version 2
Highest subscript < number of initialValues by 1
Programming with Microsoft Visual Basic 2005, Third Edition

11. Storing Data in a One-Dimensional Array
Most common way to enter data into an array
Use an assignment statement
Syntax: arrayname(subscript) = value
Examples
cities(0) = “Madrid” cities(1) = “Paris” cities(2) = “Rome”
Assigns three strings to the cities array
Programming with Microsoft Visual Basic 2005, Third Edition

12. Manipulating One-Dimensional Arrays
Tasks performed with a one-dimensional array
Display the contents of an array
Access an array element using its subscript
Search the array
Calculate average of data stored in a numeric array
Find the highest value stored in an array
Update the array elements
Sort the array elements
Programming with Microsoft Visual Basic 2005, Third Edition

13. Displaying the Contents of a One-Dimensional Array
Refer to the Months application
MainForm’s Load event procedure uses arrays
Array named months declared with initial values
Array values transferred to list box in For…Next loop
First item in list box selected as default display value
Programming with Microsoft Visual Basic 2005, Third Edition

14. Displaying the Contents of a One-Dimensional Array (continued)
Figure 9-7: Code for the MainForm’s Load event procedure
Programming with Microsoft Visual Basic 2005, Third Edition

15. The For Each…Next Statement
Used to traverse an entire array
Convenience factor relative to the For…Next loop
Handles coding of starting and ending subscripts
Programmer relieved of using extra array notation
Example
For Each monthName As String In months Me.xMonthListBox.Items.Add(monthName) Next monthName
Programming with Microsoft Visual Basic 2005, Third Edition

16. Using the Subscript to Access an Element in a One-Dimensional Array
Salary code application used by XYZ Corporation
Managers are classified by salary codes 1 through 6
Salary code is entered by the user
Salary linked to code is displayed with button click
xDisplayButton’s Click event procedure
Initializes an array to store salary values
Uses input salary code to access array elements
Programming with Microsoft Visual Basic 2005, Third Edition

17. Figure 9-10: Pseudocode for the xDisplayButton’s Click event procedure
Using the Subscript to Access an Element in a One-Dimensional Array (continued)
Figure 9-10: Pseudocode for the xDisplayButton’s Click event procedure
Programming with Microsoft Visual Basic 2005, Third Edition

18. Searching a One-Dimensional Array
Application for sales manager at Jacobsen Motors
Sales manager enters a sales amount
Sales manager presses Search button
Number of salespeople selling > amount are displayed
xSearchButton’s Click event procedure
Searches an array for values > input sales amount
Displays number of sales amounts > input amount
Programming with Microsoft Visual Basic 2005, Third Edition

19. Searching a One-Dimensional Array (continued)
Figure 9-14: Code for the xSearchButton’s Click event procedure
Programming with Microsoft Visual Basic 2005, Third Edition

20. Calculating the Average Amount Stored in a One-Dimensional Numeric Array
Application ordered by Professor Jeremiah
Calculates and displays average test scores
xCalcAvgButton’s Click event procedure
Adds the test scores stored in an array
Divides the total from step 1 by length of array
Displays the average test score
Syntax of Length property: arrayname.Length
Programming with Microsoft Visual Basic 2005, Third Edition

21. Calculating the Average Amount Stored in a One-Dimensional Numeric Array (continued)
Figure 9-17: Code for the xCalcButton’s Click event procedure
Programming with Microsoft Visual Basic 2005, Third Edition

22. Determining the Highest Value Stored in a One-Dimensional Array
Application ordered by Sharon Johnson
Displays highest amount she has earned in a week
xHighestButton’s Click event procedure
Searches the array, looking for the highest amount
Displays the highest amount
Programming with Microsoft Visual Basic 2005, Third Edition

23. Figure 9-20: Code for the xHighButton’s Click event procedure
Determining the Highest Value Stored in a One-Dimensional Array (continued)
Figure 9-20: Code for the xHighButton’s Click event procedure
Programming with Microsoft Visual Basic 2005, Third Edition

24. Updating the Values Stored in a One-Dimensional Array
Application for sales manager at Jillian Company
Used to raise price of each item the company sells
Displays each item’s new price in a label control
xUpdateButton’s Click event procedure
Stores original prices in an array
Retrieves amount of increase input to text box
Adds amount of increase to each array element
Displays each new value stored in the array
Programming with Microsoft Visual Basic 2005, Third Edition

25. Updating the Values Stored in a One-Dimensional Array (continued)
Figure 9-23: Code for the xUpdateButton’s Click event procedure
Programming with Microsoft Visual Basic 2005, Third Edition

26. Sorting the Data Stored in a One-Dimensional Array
Sorting: arranging data in a specific order
Array.Sort method
Sort elements of 1-D array in ascending order
Syntax: Array.Sort(arrayname)
Sorting an array in descending order
First use Array.sort to sort in ascending order
Then use Array.reverse to reverse array elements
Programming with Microsoft Visual Basic 2005, Third Edition

27. Sorting the Data Stored in a One-Dimensional Array (continued)
Figure 9-24: Sample run of the State application
Programming with Microsoft Visual Basic 2005, Third Edition

28. Summary – Lesson A
An array groups variables with the same data type under one name
An individual array variable is also called an element
To refer to an array element, use the array’s name followed by the element’s subscript
Arrays may be declared with or without a list of initial values
Values can be assigned to an array after declaration
Programming with Microsoft Visual Basic 2005, Third Edition

29. Summary – Lesson A (continued)
The Length property of an array returns array size
Traverse an array using a For…Next or For Each…Next statement
Array.Sort: sorts elements in ascending order
Array.Reverse: reverses the order of array elements
Programming with Microsoft Visual Basic 2005, Third Edition

30. Parallel One-Dimensional Arrays Lesson B Objectives
Create parallel one-dimensional arrays
Locate information in two parallel one-dimensional arrays
Programming with Microsoft Visual Basic 2005, Third Edition

31. Using Parallel One-Dimensional Arrays
Two or more arrays whose elements are correlated
Scenario involving two parallel arrays
Parallel arrays are named ids and prices
Each ids element corresponds to a prices element
To view an item price, search ids array for item ID
If ID exists, access and display price in prices array
Programming with Microsoft Visual Basic 2005, Third Edition

32. Parallel One-Dimensional Arrays (continued)
Figure 9-27: Illustration of a price list stored in two one-dimensional arrays
Programming with Microsoft Visual Basic 2005, Third Edition

33. Parallel One-Dimensional Arrays (continued)
Figure 9-28: Sample run of the Price List application
Programming with Microsoft Visual Basic 2005, Third Edition

34. Parallel One-Dimensional Arrays (continued)
Figure 9-29: Pseudocode for the xDisplayButton’s Click event procedure
Programming with Microsoft Visual Basic 2005, Third Edition

35. Summary – Lesson B
The elements in parallel one-dimensional arrays are correlated
To create parallel one-dimensional arrays, create two one-dimensional arrays with same size
Programming with Microsoft Visual Basic 2005, Third Edition

36. Two-Dimensional Arrays Lesson C Objectives
Create and initialize a two-dimensional array
Store data in a two-dimensional array
Search a two-dimensional array
Determine the highest and lowest subscript in a two-dimensional array
Programming with Microsoft Visual Basic 2005, Third Edition

37. Using Two-Dimensional Arrays
Stores variables (elements) in rows and columns
Resembles a table
How to identify an two-dimensional array element
Use a unique combination of two subscripts
Subscripts specify element’s row and column position
Example: products(1,2) refers to row two, column three
Programming with Microsoft Visual Basic 2005, Third Edition

38. Using Two-Dimensional Arrays (continued)
Figure 9-34: Names of some of the variables contained in the products array
Programming with Microsoft Visual Basic 2005, Third Edition

39. Using Two-Dimensional Arrays (continued)
Figure 9-35: Syntax versions and examples of declaring a two-dimensional array
Programming with Microsoft Visual Basic 2005, Third Edition

40. Storing Data in a Two-Dimensional Array
Assign values using an assignment statement
Assignment statement syntax
arrayname(rowSubscript, columnSubscript) = value
rowSubscript: horizontal subscript
columnSubscript: vertical subscript
Programming with Microsoft Visual Basic 2005, Third Edition

41. Storing Data in a Two-Dimensional Array (continued)
Figure 9-36: Syntax and examples of assignment statements used to enter data into a two-dimensional array
Programming with Microsoft Visual Basic 2005, Third Edition

42. Searching a Two-Dimensional Array
Two-dimensional arrays versus parallel arrays
Both can represent data in tabular format
Two-dimensional arrays are easier to code, use, read
New version of application for Takoda Tapahe
One two-dimensional array stores price list
2-D array replaces two parallel arrays in first version
xDisplayButton Click event procedure reflects change
Programming with Microsoft Visual Basic 2005, Third Edition

43. Searching a Two-Dimensional Array (continued)
Figure 9-38: Modified pseudocode for the xDisplayButton’s Click event procedure
Programming with Microsoft Visual Basic 2005, Third Edition

44. The Perrytown Gift Shop Application
Application for Perrytown Gift Shop
Ordered by the owner, John Blackfeather
Used to calculate weekly federal withholding tax
Requirements of application
Allow user to enter taxable wages in text box
Enable user to specify marital status
Given complete input, calculate and display tax
Programming with Microsoft Visual Basic 2005, Third Edition

45. The Perrytown Gift Shop (continued)
Figure 9-40: Interface for Perrytown Gift Shop application
Programming with Microsoft Visual Basic 2005, Third Edition

46. The Perrytown Gift Shop (continued)
Figure 9-42: Code to declare and initialize the two-dimensional arrays
Programming with Microsoft Visual Basic 2005, Third Edition

47. Coding the xCalcButton Click Event Procedure
Main tasks for xCalcButton Click event procedure
Calculate the federal withholding tax (FWT)
Display the calculated amount in the xFwtLabel
Programming with Microsoft Visual Basic 2005, Third Edition

48. Coding the xCalcButton Click Event Procedure (continued)
Figure 9-44: Pseudocode for the xCalcButton’s Click event procedure
Programming with Microsoft Visual Basic 2005, Third Edition

49. The GetUpperBound And GetLowerBound Methods
GetUpperBound method
Returns integer indicating the highest subscript
Syntax: arrayname.GetUpperBound(dimension)
GetLowerBound method
Returns integer indicating the lowest subscript
Syntax:arrayname.GetLowerBound(dimension)
dimension argument in a two-dimensional array
0 represents the row dimension
1 represents the column dimension
Programming with Microsoft Visual Basic 2005, Third Edition

50. The GetUpperBound And GetLowerBound Methods (continued)
Figure 9-46: Syntax and examples of the GetUpperBound and GetLowerBound methods
Programming with Microsoft Visual Basic 2005, Third Edition

51. Summary – Lesson C
Two-dimensional arrays store data in rows and columns
Visualize a two-dimensional array as a table
Refer to an element in a two-dimensional array using row and column subscripts
GetUpperBound method returns highest subscript
GetLowerBound method returns lowest subscript
Programming with Microsoft Visual Basic 2005, Third Edition