1. Microsoft Visual Basic 2010: Reloaded Fourth Edition
Chapter Nine
Arrays

2. Objectives After studying this chapter, you should be able to:
Declare and initialize a one-dimensional array
Store data in a one-dimensional array
Determine the number of array elements and the highest subscript
Traverse a one-dimensional array
Code a loop using the For Each…Next statement
Compute the total and average of a one-dimensional array’s contents
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

3. Objectives (cont'd.) Find the highest value in a one-dimensional array
Associate a list box with a one-dimensional array
Use a one-dimensional array as an accumulator
Sort a one-dimensional array
Create and initialize a two-dimensional array
Store data in a two-dimensional array
Sum the values in a two-dimensional array
Search a two-dimensional array
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

4. Arrays
Simple variable (or scalar variable): a variable that is unrelated to any other variable in memory
Array:
A group of variables with the same name and data type that are related in some way
Used to temporarily store related data in memory
Increases the efficiency of a program
Commonly used arrays:
One-dimensional
Two-dimensional
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

5. One-Dimensional Arrays
Can be viewed as a column of variables
Each variable in the array has the same name and data type
Subscript:
A unique number that identifies each variable in a one-dimensional array
Starts at 0 for first element in the array
Use array name and subscript to refer to each individual variable in the array
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

6. Figure 9-1: Illustration of the naming convention for the one-dimensional sales array
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

7. One-Dimensional Arrays (cont'd.)
Element: an individual variable in the array
When an array is declared:
Must specify the data type, name, and highest subscript to be used
First element has a subscript of 0
The array will contain one element more than the highest subscript because subscripts start at 0
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

8. Figure 9-2: How to declare a one-dimensional array
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

9. One-Dimensional Arrays (cont'd.)
Each element in the array is initialized if no values are provided
String array elements are initialized to the keyword Nothing
Numeric array elements are initialized to 0
Boolean array elements are initialized to False
Date array elements are initialized to 12:00 AM January 1, 0001
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

10. One-Dimensional Arrays (cont'd.)
Initial values can be specified for array elements
Populating the array: assigning initial values to an array
List the values in a comma-separated list enclosed in curly braces ({})
After declaration, can use an assignment statement to store a value in an array element
Length property: indicates number of elements
GetUpperBound method: returns the highest subscript
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

11. Figure 9-3: How to store data in a one-dimensional array
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

12. One-Dimensional Arrays (cont'd.)
Figure 9-4: How to use a one-dimensional array’s Length property
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

13. One-Dimensional Arrays (cont'd.)
Figure 9-5: How to use a one-dimensional array’s GetUpperBound method
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

14. Traversing a One-Dimensional Array
Traverse an array: look at each array element, one by one, from beginning to end of the array
Use a loop to traverse an array
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

15. Figure 9-6: How to traverse a one-dimensional array
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

16. The For Each…Next Statement
Used to code a loop that processes each element in a group or array
Creates a variable used to represent each element in the group or array
Data type of the element must match the data type of the group
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

17. The For Each…Next Statement (cont'd.)
Figure 9-7: How to use the For Each…Next statement
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

18. Starward Coffee – Calculating a Total and an Average
Figure 9-9: Problem specification for the Starward Coffee Application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

19. Starward Coffee – Calculating a Total and an Average (cont’d.)
Figure 9-8: Sample run of the Starward Coffee application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

20. Starward Coffee – Calculating a Total and an Average (cont’d.)
Figure 9-10: Partial code for the Starward Coffee application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

21. Figure 9-10: Partial code for the Starward Coffee application (cont’d
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

22. Starward Coffee – Calculating a Total and an Average (cont’d.)
Figure 9-10: Partial code for the Starward Coffee application (cont’d.)
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

23. Car-Mart – Finding the Highest Value
Figure 9-11: Problem specification for the Car-Mart application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

24. Car-Mart – Finding the Highest Value (cont’d.)
Figure 9-12: Sample run of the Car-Mart application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

25. Figure 9-13: Get Highest button’s Click event procedure
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

26. Hunt Auditorium – Arrays and Collections
Figure 9-14: Problem specification for the Hunt Auditorium application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

27. Hunt Auditorium – Arrays and Collections (cont'd.)
Figure 9-15: Sample run of the Hunt Auditorium application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

28. Hunt Auditorium – Arrays and Collections (cont'd.)
Figure 9-16: Partial code and an illustration for the Hunt Auditorium application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

29. Hunt Auditorium – Arrays and Collections (cont'd.)
Figure 9-15: Partial code and an illustration for the Hunt Auditorium application (cont’d.)
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

30. Hinsbrook School – Accumulator Array
Figure 9-17: Problem specification for the Hinsbrook School application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

31. Hinsbrook School – Accumulator Array (cont'd.)
Figure 9-18: Sample run of the Hinsbrook School application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

32. Hinsbrook School – Accumulator Array (cont'd.)
Figure 9-19: Partial code for the Hinsbrook School application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

33. Figure 9-19: Partial code for the Hinsbrook School application (cont’d
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

34. Sorting a One-Dimensional Array
Sorting: arranging data in a specific order
Ascending: first element is smallest, last element is largest
Descending: first element is largest, last element is smallest
Array.Sort method: used to sort elements in a one-dimensional array in ascending order
Array.Reverse method: used after Array.Sort method to change to descending order
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

35. Figure 9-20: How to use the Array.Sort and Array.Reverse methods
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

36. Two-Dimensional Arrays
Resembles a table with rows and columns
Each element is identified by a unique combination of two subscripts: (row, column)
Subscripts are zero-relative
Refer to an element using the name followed by the (row, column) pair in parentheses
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

37. Figure 9-21: Names of some of the variables contained in the two-dimensional orders array
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

38. Two-Dimensional Arrays (cont'd.)
Declared with highest row subscript and highest column subscript (zero-relative)
Number of rows = highest row subscript + 1
Number of columns = highest column subscript + 1
Can specify initial values for array elements
If no initial values are declared, array elements are automatically initialized
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

39. Figure 9-22: How to declare a two-dimensional array
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

40. Two-Dimensional Arrays (cont'd.)
Figure 9-23: How to store data in a two-dimensional array
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

41. Figure 9-23: How to store data in a two-dimensional array (cont’d.)
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

42. Figure 9-24: How to use a two-dimensional array’s GetUpperBound method
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

43. Traversing a Two-Dimensional Array
To traverse a two-dimensional array, use two loops:
Outer loop: tracks the row subscript
Nested loop: tracks the column subscript
Can also use a For Each…Next loop
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

44. Traversing a Two-Dimensional Array (cont'd.)
Figure 9-25: How to traverse a two-dimensional array
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

45. Figure 9-25: How to traverse a two-dimensional array (cont’d.)
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

46. Jenko Booksellers – Calculating a Total
Figure 9-26: Problem specification for the Jenko Booksellers application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

47. Jenko Booksellers – Calculating a Total (cont’d.)
Figure 9-27: Sample run of the Jenko Booksellers application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

48. Jenko Booksellers – Calculating a Total (cont’d.)
Figure 9-28: Calculate button’s Click event procedure
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

49. O’Reilly Studios – Searching a Two-Dimensional Array
Figure 9-29: Problem specification for the O’Reilly Studios application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

50. O’Reilly Studios – Searching a Two-Dimensional Array (cont’d.)
Figure 9-30: Sample run of the O’Reilly Studios application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

51. Figure 9-31: Partial code for the O’Reilly Studios application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

52. Programming Tutorial 1 Lottery Game application
Generates and displays six unique random numbers for a Lottery Game
Figure 9-33: MainForm in the Lottery Game application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

53. Programming Tutorial 2 Stay Fit Health Club application
Displays monthly fees for three different membership levels
Figure 9-33: MainForm for the Stay Fit Health Club application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

54. Programming Example Professor Coleman application
Allows a user to select a letter grade from a list box
Figure 9-43: MainForm in the Professor Coleman application
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

55. Summary Arrays: used to store related data in memory
All variables in an array have the same name and data type
To declare a one-dimensional array, provide the highest subscript or initial values
One-dimensional array: each element is uniquely identified by its position (subscript) in the array
Refer to an element in a one-dimensional array by using array name and element’s subscript
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

56. Summary (cont'd.)
Length property: returns the number of elements in an array
GetUpperBound method: returns the highest subscript in the array
Use a loop to traverse a one-dimensional array
Can use variables in an array as accumulators
Array.Sort method: sorts the elements in a one-dimensional array in ascending order
Array.Reverse method: reverses the order of elements in a one-dimensional array
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

57. Summary (cont'd.)
Two-dimensional array: each element is uniquely identified by its position (row and column subscripts) in the array
To declare a two-dimensional array, provide the highest row and column subscripts or initial values
Number of rows in a two-dimensional array is the highest row subscript value + 1
Number of columns in a two-dimensional array is the highest column subscript value + 1
Microsoft Visual Basic 2010: Reloaded, Fourth Edition

58. Summary (cont'd.)
Refer to an element in a two-dimensional array by using array name and element’s row and column subscripts separated by a comma
Use a two-dimensional array’s GetUpperBound method to determine the highest row subscript and the highest column subscript in the array
Can traverse a two-dimensional array using either two loops (outer loop and nested loop) or the For Each…Next statement
Microsoft Visual Basic 2010: Reloaded, Fourth Edition