1. 1 Web-Enabled Decision Support Systems Visual Basic.NET Programming Language Prof. Name name@email.com Position (123) 456-7890 University Name

2. 2 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

3. 3 Introduction  A computer program is a sequence of precise, unambiguous, and detailed instructions on how to complete a task, written in a language that can be interpreted by a computer –A programming language is language used to express these instructions  Visual Basic is an example of one such programming language –Visual Basic statements are similar to sentences in English  Have specific syntax, nouns, verbs, etc.  Grouped into subroutines, functions, and modules to enhance the readability and flow of logic of an application

4. 4 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

5. 5 Visual Basic Statements  A Visual Basic statement is a complete instruction written in the VB language –Language syntax are the rules and regulations that govern the composition of VB statements –Each statement contains one or more of the following elements:  Keywords: Reserved words of the language  Variables: Containers for values  Constants: Special variables with fixed values  Operators: Symbols used to perform arithmetic and logical operations  Operands: Numerical or string values that may be parts of expressions  Expressions: Combinations of one or more of the above terms that yields a value

6. 6 Keywords  Keywords are the reserved words of a programming language –Convey the same specific meaning every time they are used Visual Basic Code Example Visual Basic Keywords

7. 7 Variables  A variable is a temporary name given to a memory location –When writing a program, we need to store, manipulate, and reuse intermediate data values –Variables can temporarily store values and thus act like containers  We use the keyword Dim to declare variables in Visual Basic –Allocates or reserves the space for values to be stored –Variable declaration syntax: –Examples:

8. 8 Constants  A constant is a special type of variable whose value is not allowed to change once it has been assigned –We use the keyword Const to declare constants in Visual Basic –Constant declaration syntax: –Examples:  Visual Basic features two kinds of statements: –Declaration statements name and create variables, determine their types, and assign initial values –Executable statements perform an action that generates an output and can be stored in declared variables

9. 9 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

10. 10 InputBox and MessageBox  The InputBox function prompts an input dialog box and waits for the user input –When the user clicks the OK button on the input dialog box, the function returns the input value –Syntax:  The MessageBox function is used to display a message to the user in an output dialog box –Syntax:

11. 11 Hands-On Tutorial: User Input/Output  How-to: Use Visual Basic InputBox and MessageBox Functions 1.Create a new Visual Basic project named VisualBasicIntro. 2.Add a new Button control to the default form. Set the Text property of the button to “Temperature Conversion” and name it, cmdConvert. Use the GroupBox control with no text value around the Button control. User Input/Output: Design Window

12. 12 Adding Code Using the Code Window 3.Double-click the Button control to open the Code Window with the cmdConvert _Click subroutine. 4.Declare the variables TemperatureC and TemperatureF as Integers, and write conversion logic as shown below. User Input/Output: Code Window

13. 13 Saving and Running the Application 5.Save and run the application to view the output shown below. User Input/Output: Application Output

14. 14 The InputBox Function  InputBox syntax: –Elements:  Prompt: A string that appears as a text inside the dialog box that prompts the user  Title: A string that appears in the title bar of the dialog box  Default: The default value of the InputBox, displayed when the dialog box is shown to the user  X-Pos, Y-Pos: Integer values for X and Y co-ordinates for positioning the dialog box on the screen  Examples:

15. 15 The MessageBox Function  MessageBox syntax: –Elements:  Message: The text to display (may may be a string, integer, variable, or some combination of these)  Title: A string that appears as a text in the title bar of the dialog box  Type: The type of MessageBox  Icon: Icon for the MessageBox  Examples:

16. 16 MessageBox Options MessageBox Buttons and Icons

17. 17 Visual Basic’s Online Help  The Visual Studio IDE assists us in the process of application development, making it an interactive process –Tool Tips provide help on the syntax of statements –IntelliSense intelligently displays only the relevant methods or options Example of Online Tool Tip The MessageBox IntelliSense

18. 18 Adding Comments to Visual Basic Code  Comments are text lines that begin with a single quote or apostrophe (‘) character –Used to write useful explanatory comments along with the code lines –Ignored while the program is executing –Examples:

19. 19 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

20. 20 Visual Basic Data Types  When we declare a new variable, we must specify its data type –Indicates the kind of data that will be stored in the variable Visual Basic Data Types

21. 21 Checking and Converting Data Types  Two common operations are associated with data types: –Checking existing data types –Converting to other data types  Visual Basic provides excellent support for data type manipulations with its dozens of built-in functions  Checking functions are also known as logical functions, as they check for a particular data type and return a logical True or False value –Examples:

22. 22 Conversion Functions  Examples:  There is a generic function, CType, for data type conversions: –Syntax:

23. 23 Hands-On Tutorial: Data Type Conversion  How-to: Use Data Type Conversion Functions 1.Continue with the VisualBasicIntro project and Form1 from the “Temperature Conversion” hands-on tutorial. Add a cmdDataTypeConvert command button, and change the Text property to “Data Type Conversion”. Use the GroupBox control with no text value around the Button control. Data Type Conversion Example: Design Window

24. 24 Adding Code 2.Associate the code below with the newly added command button. Data Type Conversion Example: Code Window

25. 25 Running the Application 3.Press Ctrl+F5 to run and test the application. Data Type Conversion Example: Application Output

26. 26 Hands-On Tutorial: Data Type Checking  How-to: Use Data Type Checking Functions 1.Continue with Form1 from the previous hands-on tutorial. This time add a cmdDataTypeChk command button; change its Text property to “Data Type Checking”. Data Type Checking Example: Design View

27. 27 Adding Code and Running 2.Associate the code below with the cmdDataTypeChk_Click event. 3.Save and run the application. Data Type Checking Example: Code Window Data Type Checking Example: Output Window

28. 28 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

29. 29 Adding Windows Forms  How-to: Add a Windows Form to the Existing Project 1.Choose Project | Add Windows Form from the Main menu to open the Add New Item dialog box. 2.Select Windows Form in the templates area of the window; accept the default form name and click the Add button. Adding a New Windows Form

30. 30 Setting Start-up Form  How-to: Set the Start-up Form 1.Choose Project | Properties from the Main menu to open the Properties page. 2.Select the desired startup form from the “Startup form” drop down list. Press Ctrl+S to save the settings. Setting the Startup Form

31. 31 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

32. 32 Control Structures  Control structures allow us to control the flow of program execution –By default, a program is executed sequentially:  Left to right  Top to bottom –Control structures allow us to skip over or loop a given section of the code –Classified into two categories:  Decision structures: Allow us to test conditions  Loop structures: Allow us to execute one or more lines of code repetitively

33. 33 If-Then  We use an If-Then structure to execute one or more statements conditionally –Syntax: –Examples:

34. 34 If-Then-Else  The Else statement allows us to specify the action to be performed if the condition of the If statement is not satisfied –Syntax: –Example:

35. 35 If-Then-Else – Logical Flow Chart If-Then-Else Structure’s Logical Flow Chart

36. 36 If-Then-ElseIf-Else  We can use an If-Then-ElseIf-Else statement to apply multi-level selections –Syntax: –Example:

37. 37 The RadioButton Control  RadioButton controls force their users to select from a set of two or more mutually exclusive choices –Often used properties and events of a RadioButton control: –Example: RadioButton Control Example

38. 38 Hands-On Tutorial: Using If-Then-Else Structure  How-to: Use the If-Then-Else Control Structure and RadioButton Control 1.Design Form2 as shown below. Make Form2 the start-up form. Name the three RadioButton controls as: radBS, radMS and radPhD, and name the Button control as cmdCheckStatus. RadioButton Control Example: Degree Selection

39. 39 Adding Code and Running 2.Associate the code below with the command button’s Click event. 3.Save, run, and test the application. Code Window Application Output

40. 40 Using Select-Case Structures  The Select-Case structure selectively executes one among multiple “cases” –A single test expression is evaluated once and compared with the values of each case clause in the structure  Only the first matching case gets executed –Conceptually similar to the If-Then-Else structure  Enhances code readability when there are several possibilities to consider –Syntax:

41. 41 Select-Case Structure - Flowchart Select-Case Structure’s Logical Flow Chart

42. 42 Select-Case Structure - Example  Numbers a and b and operator op (+, -, *, /) are user inputs –Depending upon the input operator, we can perform the correct operation using a case statement as follows:

43. 43 The TextBox Control  A TextBox control is a box-shaped control that can display text data or allow the user to input the text data –Can have multiple lines and scroll bars –Can be made read-only –Most important property is Text, which allows us to access the text value Example of a TextBox Control

44. 44 Hands-On Tutorial: Working with Select-Case Structure  How-to: Use the Select-Case Control Structure and TextBox Control 1.Add a new form, Form3, to the VisualBasicIntro project and set Form3 as the start-up form. Add a TextBox named txtMonthAbbr and a command button, cmdCheckDays. 2.Design the form as shown below. Select-Case Structure Example: Design View

45. 45 Adding Code and Running 3.Use the code shown below for the Click event of the command button. Save, run, and test the application. Select-Case Structure Example: Code Window

46. 46 Loop Structures  Loop structures are used to execute blocks of statements multiple times –Here, we discuss four types:  Do-Loop-While, Do-While-Loop, Do-Loop-Until, and Do-Until-Loop –Each variant evaluates a Boolean condition to determine whether or not to continue the execution of the loop –Categorize by when the Boolean condition is checked:  Prior to loop execution: Do-While-Loop and Do-Until-Loop  After the loop execution: Do-Loop-While and Do-Loop-Until –Categorize by how the Boolean condition is interpreted:  Continue loop execution while the condition is true, stop once it is false: Do-While- Loop and Do-Loop-While  Continue loop execution until the condition is false, stop once it is true: Do-Until- Loop and Do-Loop-Until

47. 47 Logical Flow Charts Do-Loop-While and Do-While-Loop: Logical Flow Charts

48. 48 Do-Loop-While  Syntax:  Example:

49. 49 Do-While-Loop  Syntax:  Example:

50. 50 Do-Loop-Until  Syntax:  Example:

51. 51 Do-Until-Loop  Syntax:  Example:

52. 52 Hands-On Tutorial: Working with Do-Loop Structure  How-to: Use the Do-Loop Control Structure 1.Add a new form, Form4, to the existing project. Set Form4 as a startup form. 2.Add three TextBox controls named txtFirstNum, txtSecondNum and txtSumStep. Also add a Button control named cmdSum. Sum Using Do-Loop-While Structure: Design Window and Output

53. 53 Adding Code and Running 3.Use the code below for the Click event of the cmdSum Button control. 4.Save, run, and test the application.

54. 54 Alternative Coding  Do-While-Loop:  Do-Until-Loop:  Do-Loop-Until:

55. 55 For-Next Structures  The Do-Loop structures works well when we do not know how many times we must execute the loop statements  For-Next is an alternative when we know the specific number of times we want to execute the loop –Syntax: –Example:

56. 56 For-Next Structure – Logical Flow Chart For-Next Structure’s Logical Flow Chart

57. 57 Hands-On Tutorial: Working with the For-Next Loop Structure  How-to: Use the For-Next Control Structure 1.Add a new form, Form5, to the existing project. Set the Form5 as a startup form. Set up this form and form controls as shown below. For-Next Loop Structure Example: Design View

58. 58 Adding Code and Running 2.Use the code below for the Click event of the command button. 3.Save, run, and test the application.

59. 59 For-Each-Next Loop Structure  The For-Each-Next structure syntax is essentially the same as the For- Next syntax except that the loop is executed for each element of the group instead of a specific number of times –Helpful if we need to perform operations on groups such as CheckBoxes –Syntax: –Example:

60. 60 The Exit Statement  The Exit statement allows us to end the execution of a loop, subroutine, or function –Syntax: –Examples:  Exit Sub  Exit Select  Exit Do  Exit For  Exit Function

61. 61 Exit Statement - Example  “Exit Sub” example:

62. 62 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

63. 63 Arithmetic Operators  Arithmetic operators operate on one or more operands to produce an output value Arithmetic Operators (in order of precedence)

64. 64 Logical Operators

65. 65 Math Functions  Some of the functions associated with the Math collection: –Abs: Returns the absolute value of a specified –Sin, Tan, Cos: Returns the sine, tangent, and cosine values of the angle –Min, Max: Returns the smaller and greater of the given two numbers –Floor: Returns the greatest integer less than or equal to its numeric argument –Ceiling: Returns the smallest integer greater than or equal to its numeric argument –Sqrt: Returns the square root of the specified number –Pow: Returns the specified number raised to the specified power

66. 66 Math Functions - Example  We illustrate the use of Pow and Sqrt math functions with an example of Pythagoras' Theorem: –Calculate the length of the hypotenuse (output) of a right-angled triangle, given the length of its other two sides (inputs) –Code: Pythagoras’ Theorem Example: Code Window

67. 67 Handling Strings  Working with the String data type is an important aspect of the application development process –VB.NET has tremendous support for string manipulation –We can perform a variety of operations on strings:  Change the string case  Get part of the string  Concatenate two strings  Compare two strings  Search a string

68. 68 String Operations  The following table summarizes the VB.NET String operations: String Operations

69. 69 Hands-On Tutorial: String Operations  How-to: Use String Concat, Compare, Substring, IndexOf, and Length Functions 1.Add a form, Form6, to the current project and set it as the start-up form. 2.Design the form as shown below. 3.Each of the GroupBox controls illustrates a string operation. Illustrating String Operators: The Form in Design Window

70. 70 Adding Code 4.Use the code below to assign code to the appropriate command buttons. Illustrating String Operators: Code Window1

71. 71 Adding Code (cont.) 4.Use the code below to assign code to the appropriate command buttons. Illustrating String Operators: Code Window2

72. 72 Save and Run 5.Save, run, and test the application. Illustrating String Operators: Application Output

73. 73 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

74. 74 Arrays  An array is a basic data structure that allows us to refer to multiple variables by the same name –All the variables (or elements) in an array have the same data type –Array declaration syntax: –Examples: –Indexing: Example of an Integer Array

75. 75 Hands-On Tutorial: Working with Arrays  How-to: Declare and Use Arrays 1.Add a new form, Form7, to the existing VisualBasicIntro project. Set Form7 as the start-up form. 2.Design the form as shown below. Name the command button as, cmdPopulateArray. Set its Text property to “Populate Me”. An Array Example: Design Window

76. 76 Adding Code 3.For the Click event of the command button cmdPopulateArray, write the code shown below. Array Example: Code Window

77. 77 Saving and Running 4.Save, run, and test the application. Array Example: Application Output

78. 78 The ListBox Control  The ListBox control presents a list of choices to the user –By default, the choices are displayed vertically in a single column –Some properties and methods:  SelectedItem: Gets/sets the currently selected item  SelectedIndex: Gets/sets the index of a currently selected item  Items: Gets/sets collection of all the items  Items.Clear: Clears all the items in the list  ClearSelection: Sets SelectedIndex = -1 (clears any selection) Example of a ListBox Control

79. 79 Adding Items to a ListBox  We can add items to a list at design-time using the Properties Window –Locate the Items property in the Property Window –Click the Build button in the property row to open the String Collection Editor –The editor allows us to enter item values to the list  We can also add items at run-time in the VB.NET code –Employ Items.Add method: Adding Items to a ListBox Control

80. 80 Hands-On Tutorial: Displaying Array in a ListBox Control  How-to: Add Elements to a ListBox Control 1.Add a new form, Form8, to the existing VisualBasicIntro project. Set Form8 as the start-up form. 2.Add a ListBox and Button controls as shown below. Name the Button control as cmdArray and the ListBox control as lstArray. Set the Text property of the ListBox control to “Populate Me”. Displaying Array in a ListBox Control: Design Window

81. 81 Adding Code and Running 3.Associate the code below with the Click event of the cmdArray command button. 4.Save and run the application by pressing Ctrl+F5.

82. 82 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

83. 83 Multi-Dimensional Arrays  Multi-dimensional arrays have two or more dimensions –Visualized as a grid with rows of the grid representing one of the dimensions and columns representing the other –Declaration syntax: –Example:

84. 84 Using Loops with Multi-Dimensional Arrays  We can efficiently process a multi-dimensional array by using nested For-Next loops –The code below initializes (lines 9-14) and displays (lines 16-21) the Student array

85. 85 Hands-On Tutorial: Working with Multi-Dimensional Arrays  How-to: Use Multi-Dimensional Arrays and the DataGridView Control 1.Add a new form, Form9, to the existing VisualBasicIntro project. Set Form9 as the start-up form. 2.Drag and drop a DataGridView control from the Toolbox on Form9. Name the DataGridView control dgvArray. 3.Add a Button control named cmdMultDArray to the form and set its Text property to “Enter Grades”. Displaying a Two-Dimensional Array in the DataGridView Control: Design Window

86. 86 Adding Code 4.Associate the code below with the Click event of the command button. An Example of Dynamic Arrays: Code Window

87. 87 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

88. 88 Dynamic Arrays  Dynamic arrays are arrays whose size can be changed at run-time –As opposed to static arrays which always remain the same size –Useful when we do not know the exact number of elements to be stored –Visual Basic lets us assign or change the array size at run time using the ReDim (re-declare) keyword –Re-declaration syntax:

89. 89 Dynamic Array - Example Dynamic Array Example: Form Design Dynamic Array Example: Code Window

90. 90 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

91. 91 Code Debugging  Debugging is the process of finding and fixing syntax and logical errors  Syntax errors occur because of incorrect syntax use or human errors –Visual Studio.NET assists us in detecting syntax errors as we write the code  Underlines the construct where there is a syntax error Syntax Error in the Outer For-Next Loop Structure

92. 92 Logical Errors  Logical errors arise due to flaws in the logical reasoning of an application design –Detecting and handling logical errors can be very challenging –Often result in run-time exceptions when executed Logical Error: Run-Time Error Message for IndexOutOfRange Exception

93. 93 Using Breakpoints  With breakpoints we can specify a line in the code where we want to break the execution of a program –Helps when debugging logical errors –Program execution pauses at the breakpoint so that we can observe the values of various variables at that point in time –To add/remove a breakpoint, click in the selector area of the code line Adding Breakpoints to the Code

94. 94 Breakpoint Features  Breakpoints offer many interesting features: –Break on a breakpoint conditionally –Skip a breakpoint based on how many times it was hit Breakpoint Condition Dialog Box Breakpoint Hit Count Dialog Box

95. 95 Using the Watch Window  The Watch Window is used to watch the values of different variables during the execution of a program –To open a Watch Window, we must be in debug mode  We can open a Watch Window by choosing the Debug | Windows | Watch | Watch1 option form the Main menu Opening a Watch Window

96. 96 Using the Watch Window (cont.)  In a Watch Window, we can add the names of the variables we would like to watch –The corresponding values are displayed in the Value column –Every time we break (or pause) the execution using a breakpoint, we can watch the values of variables Adding Variables to the Watch Window

97. 97 Using Debug Toolbar and Menu  As we break program execution and watch variables, we have many options available in the Debug toolbar and Debug menu: –Continue (F5) –Stop Debugging (Ctrl+Alt+Break) –Step Into (F8) –Step Over (Shift+F8) –Step Out (Ctrl+Shift+F8) The Debug Menu

98. 98 Debug Menu Options

99. 99 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

100. 100 In-Class Assignment  Create a Windows application that will compute the sum of squares of a series of numbers, given: –Starting number (SN) –Ending number (EN) –Step value (SV) –Example:  Given SN=1, EN=5, and SV=1  The series is 1,2,3,4, and 5  The sum of squares is 1+2+9+16+25=53 –Directions:  Use either a Do-While loop or a For-Next loop to compute the sum, and display it in a MessageBox to the user. Also display a series and square values in two ListBox controls.  Use a Double variable to hold the sum of squares. Also, if the value entered for EN is larger than 100,000, we exit the program without computing the sum.

101. 101 Overview  11.1 Introduction  11.2 Visual Basic Statements  11.3 InputBox and MessageBox  11.4 Visual Basic Data Types  11.5 Adding Windows Forms and Setting Start-up Form  11.6 Control Structures  11.7 Arithmetic, Logical, and String Operators  11.8 Arrays  11.9 Multi-Dimensional Arrays  11.10 Dynamic Arrays  11.11 Code Debugging  11.12 In-Class Assignment  11.13 Summary

102. 102 Summary  A computer program is a sequence of precise, unambiguous, and detailed instructions on how to complete a task, written in a language that can be interpreted by a computer. –A language used to express these instructions is referred as a programming language.  A complete instruction written in Visual Basic language is known as a Visual Basic statement. –The rules and regulations that govern the composition of VB statements are known as language syntax. –A Visual Basic statement contains one or more of the following elements:  Keywords: Reserved words for Visual Basic’s use  Variables: Containers for values; temporary names given to memory locations  Constants: Special variables with fixed values  Operators: Symbols used to perform arithmetic and logical operations on operands  Operands: Numerical or string values to operate on

103. 103 Summary (cont.)  We use the keyword Dim to declare a variable in Visual Basic. –The type of a variable (data type) indicates the kind of data that will be stored in the variable.  InputBox controls helps us obtain data from a user using a dialog box.  MessageBox controls take a value as an input parameter and display it to the user in a dialog box.  Control structures allow us to control the flow of program execution; they consist of two categories, which are based on the behavior they create: –Decision structures  Allow us to test conditions (If-Then, Select-Case) –Loop structures  Allow us to execute one or more lines of code repetitively (Do-Loops, For-Next Loops)

104. 104 Summary (cont.)  An array is a basic data structure that allows us to refer to multiple variables by the same name. –Visual Basic features two types of arrays:  A static array whose size always remains the same  A dynamic array whose size can be changed at run-time  There are two kinds of errors that can occur in a program: –Syntax errors  Occur because of incorrect syntax use or human errors –Logical (semantic) errors  Arise due to flaws in the logical reasoning of an application design  Debugging is the process of finding and fixing syntax and logical errors –Detecting and handling logical errors can be very challenging –Breakpoints and Watch Windows help detect logical errors