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

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

2 Microsoft Visual Basic 2010: Reloaded, Fourth Edition 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 2

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 Edition3

4 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 Arrays 4

5 Microsoft Visual Basic 2010: Reloaded, Fourth Edition One-Dimensional Arrays One-dimensional array: –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 5

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

7 Microsoft Visual Basic 2010: Reloaded, Fourth Edition 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 7

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

9 Microsoft Visual Basic 2010: Reloaded, Fourth Edition 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,

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 Edition10

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

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

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

14 Microsoft Visual Basic 2010: Reloaded, Fourth Edition 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 14

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

16 Microsoft Visual Basic 2010: Reloaded, Fourth Edition The For Each…Next Statement 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 16

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

34 Microsoft Visual Basic 2010: Reloaded, Fourth Edition 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 34

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

36 Microsoft Visual Basic 2010: Reloaded, Fourth Edition Two-Dimensional Arrays Two-dimensional array: –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 36

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

38 Microsoft Visual Basic 2010: Reloaded, Fourth Edition Two-Dimensional Arrays (cont'd.) Two-dimensional array: –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 38

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

40 Two-Dimensional Arrays (cont'd.) Microsoft Visual Basic 2010: Reloaded, Fourth Edition40 Figure 9-23: How to store data in a two-dimensional array

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

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

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 Edition43

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

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

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

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

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

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

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

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

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

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

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

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 Edition55

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 Edition56

57 Microsoft Visual Basic 2010: Reloaded, Fourth Edition 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

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 Edition58


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