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CS 4 Intro to Programming using Visual Basic

Outline. VB help, basic architectureFinding information (lectures)Program Development Cycle (2.1, lectures)VB Controls and Events (3.1, 3.2, lectures)VB Programming basicsStructure of VB programs (lectures)Data types, variables (3.3, 3.4, lectures)Operators (3.3, 3.4, 5.1, lectures)VB Progra

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CS 4 Intro to Programming using Visual Basic

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    1. CS 4 Intro to Programming using Visual Basic Exam 2 review Patchrawat Uthaisombut University of Pittsburgh 1

    2. Outline VB help, basic architecture Finding information (lectures) Program Development Cycle (2.1, lectures) VB Controls and Events (3.1, 3.2, lectures) VB Programming basics Structure of VB programs (lectures) Data types, variables (3.3, 3.4, lectures) Operators (3.3, 3.4, 5.1, lectures) VB Program flow control If blocks, Select Case Blocks (5.2, 5.3, lectures) Repetitions (ch 6, lectures) Debugging (lectures) P. Uthaisombut 2

    3. Where to find information Textbook Lecture slides VB help system. (local copy of MSDN library) Microsoft Developer Network Library (MSDN Library) Google search Chapter 6 - VB 2005 by Schneider 3

    4. VB Help Contents Development Tools and Languages Visual Studio Integrated Development Environment for Visual Studio Visual Basic Visual Basic Programming Guide Program Structure and Code Conventions Visual Basic Language Features Reference Samples

    5. Software Development Cycle Analyze What the program should do Design Create steps to solve problem or to perform tasks Choose the interface How the application will interact with the user Build interface and write code Create interface and write code in VB Test and debug Find and remove bugs 5 P. Uthaisombut

    6. Software Development Cycle Analyze Display “Hello World!” when the user click a button Interface 1 button and 1 textbox Design Button click event handler: displays text in textbox Build interface and write code … (in IDE) … Test and Debug … (in IDE) … 6 P. Uthaisombut

    7. VB Controls (so far) Label Textbox Listbox Button Timer Chapter 6 - VB 2005 by Schneider 7

    8. VB Controls Properties Text TextAlign Fonts ForeColor BackColor ReadOnly Visible Size Chapter 6 - VB 2005 by Schneider 8

    9. VB events (so far) Click TextChanged Leave Tick (for timer) Chapter 6 - VB 2005 by Schneider 9

    10. Outline VB help, basic architecture Finding information (lectures) Program Development Cycle (2.1, lectures) VB Controls and Events (3.1, 3.2, lectures) VB Programming basics Structure of VB programs (lectures) Data types, variables (3.3, 3.4, lectures) Operators (3.3, 3.4, 5.1, lectures) VB Program flow control If blocks, Select Case Blocks (5.2, 5.3, lectures) Repetitions (ch 6, lectures) Debugging (lectures) P. Uthaisombut 10

    11. General facts about VB Code Case INsensitive TOTAL, Total, total, ToTaL, toTAL 1 line, 1 command Comment ( ` ) Line-continuation ( _ ) 11

    12. Structure of VB Code Public Class frmStopwatch Private Sub btnStart_Click(…) Handles btnStart.Click txtSeconds.Text = "0" 'Reset Watch tmrWatch.Enabled = True End Sub Private Sub btnStop_Click(…) Handles btnStop.Click tmrWatch.Enabled = False End Sub Private Sub tmrWatch_Tick(…) Handles tmrWatch.Tick txtSeconds.Text = CStr((CDbl(txtSeconds.Text) + 0.1)) End Sub End Class 12

    13. Class vs End Class VB Code that belongs to a form frmStopwatch is placed between the following 2 lines. The code should be indented Public Class frmStopwatch ‘ code goes here ‘ code goes here End Class 13

    14. Sub vs End Sub VB Code that belongs to a subroutine sub1 is placed between the following 2 lines. The code should be indented Private Sub sub1() ‘ code goes here ‘ code goes here End Sub 14

    15. Event Handler If subroutine btnStart_Click is an event handler for an event btnStart.Click, it should have the clause Handles btnStart.Click after the subroutine name. Private Sub btnStart_Click(…) Handles btnStart.Click ‘ Code goes here ‘ Code goes here End Sub 15

    16. Outline VB help, basic architecture Finding information (lectures) Program Development Cycle (2.1, lectures) VB Controls and Events (3.1, 3.2, lectures) VB Programming basics Structure of VB programs (lectures) Data types, variables (3.3, 3.4, lectures) Operators (3.3, 3.4, 5.1, lectures) VB Program flow control If blocks, Select Case Blocks (5.2, 5.3, lectures) Repetitions (ch 6, lectures) Debugging (lectures) P. Uthaisombut 16

    17. Variables and Data Types A variable is a nickname to refer to a memory location in the computer. Ex: It is easier to refer to “carSpeed” than “memory location 5472”. Each variable has a data type. The data type tells us what kind of information is stored in the variable (memory location); It indicates how to interpret the information stored in the variable (as an integer, a string, etc.) In VB we have to declare a variable to be a certain data type before we can use the variable Ex: Dim carSpeed As Integer

    18. How to make sense of “x = x + 1”? In a program, “x = x + 1” does not assert that x is equal to x+1. This is an assignment statement. Suppose x refers to address 1703. And suppose that the address contains 5. To interpret this. Take the value in the address 1703. Add 1 to it. Then store the result in the address 1703. After the execution, the result is that the address 1703 will contain 6.

    19. Hierarchical summary Numbers Integers Byte, Short, Integer, Long Floating-point Single, Double Text String Char Boolean Other … 19

    20. Naming Convention for Variables Use lowercase letters except for the first letters of additional words. This is called “camel casing”. Example gradeOnFirstExam firstExamGrade windowLocation totalScore

    21. Naming Convention for Controls Use camel casing Begins with 3-4-letter prefix that indicates the type of the control Followed by short but informative word or phrases Examples btnStartClock txtCurrentTime lblUserName

    22. Some Controls and Their Prefixes

    23. Number Operators + - * / ^ Math.Sqrt(x) returns square root of x Int(x) returns the greatest integer less than or equal to x Math.Round(n,r) returns the number n rounded to r decimal places. x = 2 + 2 ? x is 4 y = 2^3 ? y is 8 z = Int(2.45) ? z is 2

    24. Increment, add to, … x += 1 ? x = x + 1 y *= x+2 ? y = y * (x + 2)

    25. String Concatenation str1 = “foot” str2 = “ball” str3 = str1 & str2 ? str3 is “footbal” str2 &= “ “ & str3 ? str3 is “ball football” acc = 3.2 op = 1.5 acc += op ? acc is 4.7 str = "op + is acc") ? “op + is acc” str = "op" & " + is " & "acc") ? “op + is acc” str = op & "+ is" & acc) ? “4.7+ is3.2” str = op & " + is " & acc) ? “4.7 + is 3.2” 25

    26. String functions Dim str1 As String str1 = “abcdefghij” str1.Length is 10 str1.SubString(0,3) is “abc” str1.SubString(3,3) is “def” str1.IndexOf(“ab”) is 0 str1.IndexOf(“def”) is 3 str1.IndexOf(“fed”) is -1 str1.ToUpper is “ABCDEFGHIJ” “HeLLo”.ToLower is “hello” “ test test “.Trim is “test test” 26

    27. String functions Concatenating strings & (p91) Converting strings to numbers CDbl (p90) Converting numbers to strings CStr (p90) Other strings functions (p92) Length, ToUpper, ToLower, Trim SubString, IndexOf Empty string (p95) Empty string. Textbox’s Clear() method. 27

    28. Outline VB help, basic architecture Finding information (lectures) Program Development Cycle (2.1, lectures) VB Controls and Events (3.1, 3.2, lectures) VB Programming basics Structure of VB programs (lectures) Data types, variables (3.3, 3.4, lectures) Operators (3.3, 3.4, 5.1, lectures) VB Program flow control If blocks, Select Case Blocks (5.2, 5.3, lectures) Repetitions (ch 6, lectures) Debugging (lectures) P. Uthaisombut 28

    29. Character representation P. Uthaisombut 29

    30. Chapter 5 - VB 2005 by Schneider 30 Chr Function For n between 0 and 255, Chr(n) is the string consisting of the character with ANSI value n. EXAMPLES: Chr(65) is "A" Chr(162) is "¢"

    31. Chapter 5 - VB 2005 by Schneider 31 Asc Function For a string str, Asc(str) is ANSI value of the first character of str. EXAMPLES: Asc("A") is 65 Asc("¢25") is 162

    32. Chapter 5 - VB 2005 by Schneider 32 Relational Operators < less than <= less than or equal to > greater than >= greater than or equal to = equal to <> not equal to ANSI values are used to decide order for strings.

    33. Chapter 5 - VB 2005 by Schneider 33 Logical Operators Used with Boolean expressions Not – makes a False expression True and vice versa And – will yield a True if and only if both expressions are True Or – will yield a True if at least one of both expressions are True

    34. Data type of subexpressions ( 2 < n ) And ( n < 5 ) Integer Integer Integer Integer Boolean Boolean Boolean P. Uthaisombut 34

    35. guess <> secret NOT (guess = secret) (guess < secret) OR (guess > secret) P. Uthaisombut 35

    36. Outline VB help, basic architecture Finding information (lectures) Program Development Cycle (2.1, lectures) VB Controls and Events (3.1, 3.2, lectures) VB Programming basics Structure of VB programs (lectures) Data types, variables (3.3, 3.4, lectures) Operators (3.3, 3.4, 5.1, lectures) VB Program flow control If blocks, Select Case Blocks (5.2, 5.3, lectures) Repetitions (ch 6, lectures) Debugging (lectures) P. Uthaisombut 36

    37. Chapter 5 - VB 2005 by Schneider 37 If Block The program will take a course of action based on whether a condition is true. If condition Then action1 Else action2 End If

    38. Chapter 5 - VB 2005 by Schneider 38 Another example If block If condition Then action1 End If Statement2 Statement3

    39. ElseIf clause If condition1 Then action1 Else If condition2 Then action2 Else If condition3 Then action3 Else action4 End If EndIf EndIf If condition1 Then action1 ElseIf condition2 Then action2 ElseIf condition3 Then action3 Else action4 End If Schneider & Uthaisombut 39 An extension of the If block allows for more than two possible alternatives with the inclusion of ElseIf clauses. Note: there is no space between the word "Else" and "If" Only one "End If" is required.An extension of the If block allows for more than two possible alternatives with the inclusion of ElseIf clauses. Note: there is no space between the word "Else" and "If" Only one "End If" is required.

    40. Example from Guess-A-Number Here, we assume that guess is not equal to secret. Otherwise, the game should have already terminated. If guess < secret Then ` too small Else If guess > secret Then ` too big Endif EndIf If guess < secret Then ` too small EndIf If guess > secret Then ` too big EndIf ------------------------- If guess < secret Then ` too small Else ` too big EndIf

    41. Simplified Nested If Statement If A < B Then If A < C Then (A is smallest) Else (C is smallest) End If Else If B < C Then (B is smallest) Else (C is smallest) End If End If If A < B And A < C Then (A is smallest) ElseIf B < A And B < C Then (B is smallest) Else (C is smallest) End If (Assume A,B,C are not equal) Schneider & Uthaisombut 41

    42. Chapter 5 - VB 2005 by Schneider 42 Example 3: Partial Code Dim x As Integer = 2, y As Integer = 3 Select Case num Case y - x, x txtPhrase.Text = "Buckle my shoe." Case Is <= 4 txtPhrase.Text = "Shut the door." Case x + y To x * y txtPhrase.Text = "Pick up sticks." Case 7, 8 txtPhrase.Text = "Lay them straight." Case Else txtPhrase.Text = "Start all over again." End Select

    43. Outline VB help, basic architecture Finding information (lectures) Program Development Cycle (2.1, lectures) VB Controls and Events (3.1, 3.2, lectures) VB Programming basics Structure of VB programs (lectures) Data types, variables (3.3, 3.4, lectures) Operators (3.3, 3.4, 5.1, lectures) VB Program flow control If blocks, Select Case Blocks (5.2, 5.3, lectures) Repetitions (ch 6, lectures) Debugging (lectures) P. Uthaisombut 43

    44. Chapter 6 - VB 2005 by Schneider 44 Do Loop Syntax Do While condition statement(s) Loop A Do statement precedes the sequence of statements, and a Loop statement follows the sequence of statements. The condition, preceded by either the word “While” or the word “Until”, follows the word “Do” or the word “Loop”. A Do statement precedes the sequence of statements, and a Loop statement follows the sequence of statements. The condition, preceded by either the word “While” or the word “Until”, follows the word “Do” or the word “Loop”.

    45. Chapter 6 - VB 2005 by Schneider 45 Pseudocode and Flow Chart for a Do Loop

    46. Dim num As Integer = 1 Do While num <= 7 lstNumbers.Items.Add(num) num += 1 'Add 1 to the value of num Loop Dim x As Integer = 5 Dim y As Integer = 1 Do While y <= 12 lstTable.Items.Add(x & " * " & y & " = " & x * y) y += 1 Loop P. Uthaisombut 46

    47. Chapter 6 - VB 2005 by Schneider 47 Post Test Loop Do statement(s) Loop Until condition If condition is true, then the program continues with the line after the Loop statement. If condition is false, then the entire process is repeated beginning with the Do statement. In other words, the statements inside the loop are executed once and then are repeatedly executed until the condition is true.If condition is true, then the program continues with the line after the Loop statement. If condition is false, then the entire process is repeated beginning with the Do statement. In other words, the statements inside the loop are executed once and then are repeatedly executed until the condition is true.

    48. Chapter 6 - VB 2005 by Schneider 48 Pseudocode and Flowchart for a Post-Test Loop

    49. Chapter 6 - VB 2005 by Schneider 49 Example: Repeat Request Until Proper Response is Given Do passWord = InputBox("What is the password?") passWord = passWord.ToUpper Loop Until passWord = "SHAZAM"

    50. secretNum = CInt(Int(Rnd() * 5 + 1)) Do guessNum = Cint(InputBox("Guess.")) Loop Until guessNum = secretNum MsgBox(“You are right!”); -------------------------------------------------- secretNum = CInt(Int(Rnd() * 5 + 1)) guessNum = CInt(InputBox(“Guess.“) Do While guessNum <> secretNum guessNum = Cint(InputBox(“Wrong. Guess again.")) Loop MsgBox(“You are right!”); P. Uthaisombut 50

    51. Outline VB help, basic architecture Finding information (lectures) Program Development Cycle (2.1, lectures) VB Controls and Events (3.1, 3.2, lectures) VB Programming basics Structure of VB programs (lectures) Data types, variables (3.3, 3.4, lectures) Operators (3.3, 3.4, 5.1, lectures) VB Program flow control If blocks, Select Case Blocks (5.2, 5.3, lectures) Repetitions (ch 6, lectures) Debugging (lectures) P. Uthaisombut 51

    52. Tracing Perform one statement at a time. After each statement, the debugger will stop the program to allow the programmer to inspect the state of the program. Break points Statements in the program where the programmer has previously specified set. When the program reaches a break point, it stops. This allows the programmer to inspect the state of the program

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