Programming with Microsoft Visual Basic 2008 Fourth Edition

1. Programming with Microsoft Visual Basic 2008 Fourth Edition Chapter Nine Arrays

2. Previewing the Treasures Gift Shop Application Treasures application: Allows the user to enter a product ID, then displays the product’s price Open the Treasures.exe file Programming with Microsoft Visual Basic 2008, Fourth Edition 2

3. Previewing the Treasures Gift Shop Application (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 3

4. Lesson A Objectives After studying Lesson A, 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 Programming with Microsoft Visual Basic 2008, Fourth Edition 4

5. 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 2008, Fourth Edition 5

6. Using Arrays Simple (scalar) variable: One that is unrelated to any other variable in memory Array: Group of variables that have same name and same data type and are related in some way Reasons to use arrays: Simplifies process of coding application Increases run-time efficiency of program Programming with Microsoft Visual Basic 2008, Fourth Edition 6

7. One-Dimensional Arrays One-dimensional array: Sequence of contiguous memory cells Visualized as a column of variables Subscript: Integer identifying array variable Starts at 0 for first array variable Refer to array variable by array name and subscript Example: strCities(0) is first variable in states array Programming with Microsoft Visual Basic 2008, Fourth Edition 7

8. One-Dimensional Arrays (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 8

9. One-Dimensional Arrays (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 9

10. One-Dimensional Arrays (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 10

11. One-Dimensional Arrays (continued) Element: Refers to individual array variable Arrays are initialized by computer when created: Arrays of numeric variables are initialized to 0 Arrays of string variables are initialized using keyword Nothing Arrays of Boolean variables are initialized to False Arrays of Date variables are initialized to 12:00 AM January 1, 0001 Populating the array: Assigning initial values Programming with Microsoft Visual Basic 2008, Fourth Edition 11

12. One-Dimensional Arrays (continued) After array is declared, you can store data in array To enter data into array: Use assignment statement Use TryParse statement Syntax: arrayname(subscript) = value Programming with Microsoft Visual Basic 2008, Fourth Edition 12

13. One-Dimensional Arrays (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 13

14. Manipulating One-Dimensional Arrays Tasks to be performed with one-dimensional array: Display contents of array Access array element using its subscript Search array Calculate average of data stored in numeric array Find highest value stored in array Update array elements Sort array elements Programming with Microsoft Visual Basic 2008, Fourth Edition 14

15. Displaying the Contents of a One-Dimensional Array Months application: Stores names of 12 months of year and displays them in list box The form’s Load event procedure: Declares array named strMonths, with initial values Array values are transferred to list box using For…Next loop First item in list box is selected as default display value Programming with Microsoft Visual Basic 2008, Fourth Edition 15

16. Displaying the Contents of a One-Dimensional Array (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 16

17. The For Each…Next Statement For Each…Next statement: Used to process each element in array Unlike For…Next statement: You do not have to code starting and ending subscripts You do not have to use extra array notation Declare variable within For Each…Next statement to refer to each array element, one at a time Programming with Microsoft Visual Basic 2008, Fourth Edition 17

18. Programming with Microsoft Visual Basic 2008, Fourth Edition 18 The For Each…Next Statement (continued)

19. Using the Subscript to Access an Element in a One-Dimensional Array Salary code application: Uses one-dimensional array to store six salary amounts Each salary amount is associated with code Salary code is entered by user Salary amount is displayed with button click Programming with Microsoft Visual Basic 2008, Fourth Edition 19

20. Using the Subscript to Access an Element in a One-Dimensional Array (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 20

21. Using the Subscript to Access an Element in a One-Dimensional Array (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 21

22. Determining the Length of an Array Subscript used to access array element must be at least 0 but no more than highest subscript in array Otherwise runtime error will occur Length property: Stores number of elements in array Programming with Microsoft Visual Basic 2008, Fourth Edition 22

23. Determining the Length of an Array (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 23

24. Determining the Length of an Array (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 24

25. Searching a One-Dimensional Array Sales Solution application: Sales manager enters sales amount Sales manager presses Search button Number of salespeople selling more than specified amount are displayed Programming with Microsoft Visual Basic 2008, Fourth Edition 25

26. Searching a One-Dimensional Array (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 26

27. Searching a One-Dimensional Array (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 27

28. Calculating the Average Amount Stored in a One-Dimensional Numeric Array Average application: Calculates and displays average test scores Uses four-element one-dimensional Integer array btnCalc control’s Click event procedure: Adds array element values Divides total by number of array elements Displays average test score Programming with Microsoft Visual Basic 2008, Fourth Edition 28

29. Calculating the Average Amount Stored in a One-Dimensional Numeric Array (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 29

30. Determining the Highest Value Stored in a One-Dimensional Array Highest Number application: Displays highest number stored in 10-element one-dimensional Double array btnDisplay control’s Click event procedure: Searches array, looking for highest amount Displays highest amount Programming with Microsoft Visual Basic 2008, Fourth Edition 30

31. Programming with Microsoft Visual Basic 2008, Fourth Edition 31 Determining the Highest Value Stored in a One-Dimensional Array (continued)

32. Updating the Values Stored in a One-Dimensional Array Price Increase application: Stores prices of four items in four-element, one-dimensional Decimal array Used to raise price of each item the company sells Displays each item’s new price in label control btnDisplay control’s Click event procedure: Stores original prices in array Retrieves amount of increase input to text box Adds amount of increase to each array element Displays each new value stored in array Programming with Microsoft Visual Basic 2008, Fourth Edition 32

33. Updating the Values Stored in a One-Dimensional Array (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 33

34. Updating the Values Stored in a One-Dimensional Array (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 34

35. Sorting the Data Stored in a One-Dimensional Array Sorting: Arranging data in specific order Array.Sort method: Sorts elements of one-dimensional array in ascending order Syntax: Array.Sort(arrayname) To sort array in descending order: First use Array.Sort to sort in ascending order Then use Array.Reverse to reverse order of array elements Programming with Microsoft Visual Basic 2008, Fourth Edition 35

36. Sorting the Data Stored in a One-Dimensional Array (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 36

37. Lesson A Summary An array groups variables with same data type under one name An individual array variable is also called an element Arrays may be declared with or without list of initial values Values can be assigned to array after declaration Programming with Microsoft Visual Basic 2008, Fourth Edition 37

38. Lesson A Summary (continued) Use For Each…Next statement to process instructions for each element in array To refer to array element, use array’s name followed by element’s subscript Length property of array returns array size Array.Sort: Sorts elements in ascending order Array.Reverse: Reverses order of array elements Programming with Microsoft Visual Basic 2008, Fourth Edition 38

39. Lesson B Objectives After studying Lesson B, you should be able to: Create and manipulate parallel one-dimensional arrays Locate information in two parallel one-dimensional arrays Declare and initialize a two-dimensional array Store data in a two-dimensional array Search a two-dimensional array Determine the highest subscript in a two-dimensional array Programming with Microsoft Visual Basic 2008, Fourth Edition 39

40. Parallel One-Dimensional Arrays Parallel one-dimensional arrays: Two or more arrays whose elements are related by their position in arrays (by their subscripts) Arrays may be different data types Scenario involving two parallel arrays: Parallel arrays are named strIds and intPrices Each strIds element corresponds to intPrices element Must search strIds array for item ID If ID exists, access price at same index in intPrices array Programming with Microsoft Visual Basic 2008, Fourth Edition 40

41. Parallel One-Dimensional Arrays (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 41

42. Parallel One-Dimensional Arrays (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 42

43. Parallel One-Dimensional Arrays (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 43

44. Parallel One-Dimensional Arrays (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 44

45. Two-Dimensional Arrays Two-dimensional array: Stores variables (elements) in rows and columns Resembles a table How to identify a two-dimensional array element: Use unique combination of two subscripts to specify element’s row and column position Example: strProducts(1,2) refers to row two, column three Programming with Microsoft Visual Basic 2008, Fourth Edition 45

46. Two-Dimensional Arrays (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 46

47. Two-Dimensional Arrays (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 47

48. Two-Dimensional Arrays (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 48

49. Searching a Two-Dimensional Array Two-dimensional arrays versus parallel arrays: Both can represent data in tabular format All data in two-dimensional array must be same type New version of Treasures application: Use one two-dimensional array to store price list 2-D array replaces two parallel arrays in first version Programming with Microsoft Visual Basic 2008, Fourth Edition 49

50. Searching a Two-Dimensional Array (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 50

51. The GetUpperBound Method GetUpperBound method: Returns integer indicating highest subscript in specified dimension of array Dimension will be 0 for row dimension, and 1 for column dimension Programming with Microsoft Visual Basic 2008, Fourth Edition 51

52. Programming with Microsoft Visual Basic 2008, Fourth Edition 52 The GetUpperBound Method (continued)

53. Programming with Microsoft Visual Basic 2008, Fourth Edition 53 The GetUpperBound Method (continued)

54. Lesson B Summary The elements in parallel one-dimensional arrays are related by their subscript position To create parallel one-dimensional arrays, create two one-dimensional arrays with same size A two-dimensional array contains rows and columns Use row and column subscripts to refer to element in two-dimensional array Use GetUpperBound method to determine highest subscript in specified dimension of an array Programming with Microsoft Visual Basic 2008, Fourth Edition 54

55. Lesson C Objectives After studying Lesson C, you should be able to: Create a simple smart device application Programming with Microsoft Visual Basic 2008, Fourth Edition 55

56. Creating a Smart Device Application Smart Device applications: Run on smart devices such as Pocket PCs and Smartphones Visual Studio provides emulators of devices to use for testing application In Visual Studio, select Smart Device Project template Programming with Microsoft Visual Basic 2008, Fourth Edition 56

57. Creating a Smart Device Application (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 57

58. Programming with Microsoft Visual Basic 2008, Fourth Edition 58 Creating a Smart Device Application (continued)

59. Creating a Smart Device Application (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 59

60. Creating a Smart Device Application (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 60

61. Creating a Smart Device Application (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition 61

62. Lesson C Summary To run an application on a Smart Device, use Smart Device project template Programming with Microsoft Visual Basic 2008, Fourth Edition 62