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Arrays Chapter Microsoft Visual Basic.NET: Reloaded 1.

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Presentation on theme: "Arrays Chapter Microsoft Visual Basic.NET: Reloaded 1."— Presentation transcript:

1 Arrays Chapter Microsoft Visual Basic.NET: Reloaded 1

2 2 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

3 3 Microsoft Visual Basic.NET: Reloaded Objectives ( continued ) Search a one-dimensional array Compute the average of a one-dimensional arrays contents Find the highest entry in a one-dimensional array Update the contents of a one-dimensional array Sort a one-dimensional array

4 4 Microsoft Visual Basic.NET: Reloaded Objectives ( continued ) Enter code in the forms Load event procedure 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

5 5 Microsoft Visual Basic.NET: Reloaded Using Arrays Simple variable Also called scalar variable Is unrelated to any other variable in memory Array A group of variables that have the same name and data type and are related in some way You can picture an array as a group of small adjacent boxes inside the computers memory

6 6 Microsoft Visual Basic.NET: Reloaded One-Dimensional Arrays One-dimensional array Visualize as a column of variables Each variable is identified by a unique number Unique number is called subscript Subscript is placed inside parentheses immediately following array name Example strStates(1) – read strStates sub one Individual variables referred to as elements

7 7 Microsoft Visual Basic.NET: Reloaded One-Dimensional Arrays ( continued ) Declare using keywords Dim or Private highestSubscript argument in declaration used to specify the number of elements in the array number of array elements is 1 more than the value in highestSubscript argument

8 8 Microsoft Visual Basic.NET: Reloaded One-Dimensional Arrays ( continued )

9 9 Microsoft Visual Basic.NET: Reloaded HOW TO…

10 10 Microsoft Visual Basic.NET: Reloaded Storing Data in a One-Dimensional Array

11 11 Microsoft Visual Basic.NET: Reloaded Manipulating One-Dimensional Arrays Sample procedures will demonstrate how to perform tasks using a one-dimensional array Display contents of an array Access an array element using its subscript Search the array Calculate the average of the data stored in a numeric array Find the highest value stored in an array Update the array elements Sort the array elements

12 12 Microsoft Visual Basic.NET: Reloaded Displaying the Contents of a One- Dimensional Array

13 13 Microsoft Visual Basic.NET: Reloaded Displaying the Contents of a One- Dimensional Array ( continued )

14 14 Microsoft Visual Basic.NET: Reloaded The For Each…Next Statement Use to code a loop containing instructions to be processed for each element in a group Syntax template shown in next slide contains words element and group element Declare a variable of the same data type as the elements of the array and place this variable in the element position of the template group The variable name of the array

15 15 Microsoft Visual Basic.NET: Reloaded HOW TO…

16 16 Microsoft Visual Basic.NET: Reloaded Using the Subscript to Access an Element in a One-Dimensional Array Display salary amount corresponding to code entered by user

17 17 Microsoft Visual Basic.NET: Reloaded Searching a One-Dimensional Array Determine number of salespeople selling above a certain amount

18 18 Microsoft Visual Basic.NET: Reloaded Calculating the Average Amount Stored in a One-Dimensional Numeric Array Calculate and display average test score earned by students on final exam

19 19 Microsoft Visual Basic.NET: Reloaded Determining the Highest Value Stored in a One-Dimensional Array Display highest amount earned in a week

20 20 Microsoft Visual Basic.NET: Reloaded Updating the Values Stored in a One- Dimensional Array Procedure allows manager to increase price of each item and display items new price

21 21 Microsoft Visual Basic.NET: Reloaded Sorting the Data Stored in a One- Dimensional Array Array.Sort(arrayName) method Sorts the elements of a one-dimensional array in ascending order First element contains smallest value Last element contains largest value To sort in descending order First sort in ascending order Then use Array.Reverse(arrayname) method to reverse the position of the elements in the array

22 22 Microsoft Visual Basic.NET: Reloaded Sorting the Data Stored in a One- Dimensional Array ( continued ) btnSortAscending_Click procedure sorts intNumbers array into ascending order

23 23 Microsoft Visual Basic.NET: Reloaded Sorting the Data Stored in a One- Dimensional Array ( continued )

24 24 Microsoft Visual Basic.NET: Reloaded Sorting the Data Stored in a One- Dimensional Array ( continued ) Method sorts array in descending order and displays the results

25 25 Microsoft Visual Basic.NET: Reloaded Sorting the Data Stored in a One- Dimensional Array ( continued )

26 26 Microsoft Visual Basic.NET: Reloaded Using a Module-Level One-Dimensional Array Application displays names contained in a sequential access file, giving user choice of ascending or descending order of display First, declare array variable in the Forms general declarations section Then, fill array from data in file using code in the forms Load event procedure Load event occurs before the first time a form is displayed

27 27 Microsoft Visual Basic.NET: Reloaded Using a Module-Level One-Dimensional Array ( continued )

28 28 Microsoft Visual Basic.NET: Reloaded Using a Module-Level One-Dimensional Array ( continued )

29 29 Microsoft Visual Basic.NET: Reloaded Parallel One-Dimensional Arrays Two or more one-dimensional arrays whose elements are related by their position (subscript) Called parallel because element at subscript 0 in first array corresponds to element at subscript 0 in another array Example: strID(0) corresponds to intPrice(0) and strID(1) corresponds to intPrice(1), and so on…

30 30 Microsoft Visual Basic.NET: Reloaded Parallel One-Dimensional Arrays ( continued )

31 31 Microsoft Visual Basic.NET: Reloaded Parallel One-Dimensional Arrays ( continued )

32 32 Microsoft Visual Basic.NET: Reloaded Parallel One-Dimensional Arrays ( continued )

33 33 Microsoft Visual Basic.NET: Reloaded Two-Dimensional Arrays Resemble a table in that variables are store in rows and columns Each element is identified by a unique combination of two subscripts The first subscript indicates the elements row The second subscript indicates the column Each subscript begins with 0 The element in the first row and column has a subscript of (0,0)

34 34 Microsoft Visual Basic.NET: Reloaded Two-Dimensional Arrays ( continued )

35 35 Microsoft Visual Basic.NET: Reloaded HOW TO…

36 36 Microsoft Visual Basic.NET: Reloaded Storing Data in a Two-Dimensional Array

37 37 Microsoft Visual Basic.NET: Reloaded Searching a Two-Dimensional Array

38 38 Microsoft Visual Basic.NET: Reloaded Programming Example – Perrytown Gift Shop Application Application is to assist in employee weekly payroll process Calculates and displays the federal withholding tax (FWT) Gets and displays taxable wages Gets and displays marital status

39 39 Microsoft Visual Basic.NET: Reloaded TOE Chart

40 40 Microsoft Visual Basic.NET: Reloaded User Interface

41 41 Microsoft Visual Basic.NET: Reloaded Objects, Properties, and Settings

42 42 Microsoft Visual Basic.NET: Reloaded Objects, Properties, and Settings ( continued )

43 43 Microsoft Visual Basic.NET: Reloaded Tab Order

44 44 Microsoft Visual Basic.NET: Reloaded Pseudocode btnExit Click event procedure close application btnCalc Click event procedure Include the following in a Try/Catch block: remove any dollar signs and spaces from the txtTaxable control assign the taxable wages store in txtTaxable to a variable assign the marital status entered in txtStatus to a variable if marital status is not either M or S display an appropriate message else if marital status is M use the Married tax table, stored in an array else use the singles tax table, stored in an array

45 45 Microsoft Visual Basic.NET: Reloaded Pseudocode ( continued ) end if Repeat while there are still rows in the tax table to search and taxable wages have not been found if taxable wages are less than or equal to value stored in the first column of the current row in tax table use information stored in 2 nd, 3 rd, and 4 th columns in tax table to calculate the federal withholding tax indicate that the taxable wages were found by assigning the value True to blnFound variable else add 1 to the contents of the intRow variable to continue the search row in the tax table Display the federal withholding tax in the lblFwt control Use general Catch statement to handle and display any errors

46 46 Microsoft Visual Basic.NET: Reloaded Code

47 47 Microsoft Visual Basic.NET: Reloaded Code ( continued )

48 48 Microsoft Visual Basic.NET: Reloaded Summary Programmers use arrays to temporarily store related data in computers internal memory All variables in an array have the same name and data type Each element in a one-dimensional array is identified by a unique subscript Appears in parentheses after arrays name

49 49 Microsoft Visual Basic.NET: Reloaded Summary ( continued ) Each element in a two-dimensional array is identified by a unique combination of two subscripts: Row subscript Column subscript Subscripts appear in parentheses after the arrays name You list the row subscript first, followed by a comma and the column subscript The first subscript in a one-dimensional array is 0 (zero)

50 50 Microsoft Visual Basic.NET: Reloaded Summary ( continued ) First row subscript in a two-dimensional array is 0 (zero) likewise, the first column subscript also is 0 (zero) When declaring a one-dimensional array, provide either highest subscript or initial values When declaring a two-dimensional array, you provide either the highest row and column subscripts or the initial values

51 51 Microsoft Visual Basic.NET: Reloaded Summary ( continued ) The number of elements in a one-dimensional array is one more than its highest subscript The number of rows in a two-dimensional array is one more than its highest row subscript likewise, the number of columns is one more than its highest column subscript You usually use an assignment statement to store data in an array You refer to an element in a one-dimensional array using the arrays name followed by the elements subscript

52 52 Microsoft Visual Basic.NET: Reloaded Summary ( continued ) You refer to an element in a two-dimensional array using the arrays name followed by the elements row and column subscripts, which are separated by a comma You can use the For Each…Next statement to code a loop whose instructions you want processed for each element in an array You can use the Length property to determine the number of elements in the array

53 53 Microsoft Visual Basic.NET: Reloaded Summary ( continued ) You use the Array.Sort method to sort the elements in a one-dimensional array You use the Array.Reverse method to reverse the order of the elements in an array The elements in parallel arrays are related by their subscript (or position) in each array


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