1. Microsoft Visual Basic 2005: Reloaded Second Edition
Chapter 8
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
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
Microsoft Visual Basic 2005: Reloaded, Second Edition

3. 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
Microsoft Visual Basic 2005: Reloaded, Second Edition

4. Objectives (continued)
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
Microsoft Visual Basic 2005: Reloaded, Second Edition

5. Using 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 2005: Reloaded, Second Edition

6. One-Dimensional Arrays
Can be viewed as a column of variables
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 2005: Reloaded, Second Edition

7. One-Dimensional Arrays (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

8. One-Dimensional Arrays (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

9. One-Dimensional Arrays (continued)
Element: an individual variable in the array
When an array is declared:
Each element in the array is initialized if no values are provided
Initial values can be specified for elements
Microsoft Visual Basic 2005: Reloaded, Second Edition

10. Storing Data in a One-Dimensional Array
Microsoft Visual Basic 2005: Reloaded, Second Edition

11. Manipulating One-Dimensional Arrays
Array elements can be used like any other variable
Examples:
Display the contents of an array
Access an array element using its subscript
Search the array
Calculate the average of data stored in a numeric array
Find the highest value stored in an array
Update array elements
Sort array elements
Microsoft Visual Basic 2005: Reloaded, Second Edition

12. Displaying the Contents of a One-Dimensional Array
Microsoft Visual Basic 2005: Reloaded, Second Edition

13. Displaying the Contents of a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

14. Displaying the Contents of a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

15. The For Each…Next Statement
Used to code a loop which processes each element in a group or array
Creates a variable used to represent each item in the group or array
Data type of the element must match the data type of the group
Microsoft Visual Basic 2005: Reloaded, Second Edition

16. The For Each…Next Statement (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

17. Using the Subscript to Access an Element in a One-Dimensional Array
Microsoft Visual Basic 2005: Reloaded, Second Edition

18. Using the Subscript to Access an Element … (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

19. Using the Subscript to Access an Element … (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

20. Searching a One-Dimensional Array
Microsoft Visual Basic 2005: Reloaded, Second Edition

21. Searching a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

22. Searching a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

23. Searching a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

24. Calculating the Average Amount Stored in a One-Dimensional Numeric Array
Sample application:
Find the average from an array of test scores
Length property: number of elements in the array
Microsoft Visual Basic 2005: Reloaded, Second Edition

25. Calculating the Average Amount Stored in a One-Dimensional Numeric Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

26. Calculating the Average Amount Stored in a One-Dimensional Numeric Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

27. Calculating the Average Amount Stored in a One-Dimensional Numeric Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

28. Calculating the Average Amount Stored in a One-Dimensional Numeric Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

29. Determining the Highest Value Stored in a One-Dimensional Array
Microsoft Visual Basic 2005: Reloaded, Second Edition

30. Determining the Highest Value Stored in a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

31. Determining the Highest Value Stored in a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

32. Updating the Values Stored in a One-Dimensional Array
Microsoft Visual Basic 2005: Reloaded, Second Edition

33. Updating the Values Stored in a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

34. Updating the Values Stored in a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

35. Updating the Values Stored in a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

36. Sorting the Data Stored in 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 2005: Reloaded, Second Edition

37. Sorting the Data Stored in a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

38. Sorting the Data Stored in a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

39. Sorting the Data Stored in a One-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

40. Parallel One-Dimensional Arrays
Microsoft Visual Basic 2005: Reloaded, Second Edition

41. Parallel One-Dimensional Arrays (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

42. Parallel One-Dimensional Arrays (continued)
Parallel arrays:
Two or more arrays whose elements are related by their position in the arrays
Microsoft Visual Basic 2005: Reloaded, Second Edition

43. Parallel One-Dimensional Arrays (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

44. Parallel One-Dimensional Arrays (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

45. Parallel One-Dimensional Arrays (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

46. Parallel One-Dimensional Arrays (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

47. 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
Microsoft Visual Basic 2005: Reloaded, Second Edition

48. Two-Dimensional Arrays (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

49. Two-Dimensional Arrays (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

50. Two-Dimensional Arrays (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

51. Two-Dimensional Arrays (continued)
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 2005: Reloaded, Second Edition

52. Storing Data in a Two-Dimensional Array
Microsoft Visual Basic 2005: Reloaded, Second Edition

53. Storing Data in a Two-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

54. Searching a Two-Dimensional Array
Microsoft Visual Basic 2005: Reloaded, Second Edition

55. Searching a Two-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

56. Searching a Two-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

57. Searching a Two-Dimensional Array (continued)
Microsoft Visual Basic 2005: Reloaded, Second Edition

58. Programming Tutorial
Microsoft Visual Basic 2005: Reloaded, Second Edition

59. Programming Example
Microsoft Visual Basic 2005: Reloaded, Second Edition

60. Summary
Arrays: a group of related variables with the same name and same data type
Array element: one item in the array
One-dimensional array: each element is uniquely identified by its position (subscript) in the array
Two-dimensional array: each element is uniquely identified by its position (row and column subscripts) in the array
Subscripts are zero-relative
Microsoft Visual Basic 2005: Reloaded, Second Edition

61. Summary (continued)
Number of elements in an array is the highest subscript value + 1
For Each...Next statement: used to loop through all the elements in an array
Length property: returns the number of elements in an array
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 2005: Reloaded, Second Edition