Computer Programming Concepts and Visual Basic David I. Schneider

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226 Computer Programming Concepts and Visual Basic Open file2 For Input As #2 Open file3 For Output As #3 have1data = Get1data(num1) have2data = Get2data(num2) recCount = 0 Do While have1data And have2data Select Case num1 Case Is < num2 Write #3, num1 have1data = Get1data(num1) Case Is > num2 Write #3, num2 have2data = Get2data(num2) Case num2 Write #3, num1 have1data = Get1data(num1) have2data = Get2data(num2) End Select recCount = recCount + 1 Loop Do While have1data Write #3, num1 recCount = recCount + 1 have1data = Get1data(num1) Loop Do While have2data Write #3, num2 recCount = recCount + 1 have2data = Get2data(num2) Loop Close #1, #2, #3 picProgress.Print recCount; “records written to ”; file3 End Sub Private Function Get1data(num1 As Single) As Boolean ‘If possible, read next value from file 1 ‘Return value of True when new data are read; False if data not available If Not EOF(1) Then Input #1, num1 Get1data = True Else Get1data = False End If End Function Private Function Get2data(num2 As Single) As Boolean ‘If possible, read next value from file 2 ‘Return value True when new data are read; False if data not available If Not EOF(2) Then Input #2, num2 Get2data = True Else Get2data = False End If End Function
■ CONTROL BREAK PROCESSING Suppose a small real estate company stores its sales data for a year in a sequential file in which each record contains four fields: month of sale, day of sale (1 through 31), address, and price. Typical data for the sales of the first quarter of a year are shown in Figure 7-2. The records are ordered by date of sale. Month Day Address Price January 9 102 Elm Street $203,000 January 20 1 Main Street $315,200 January 25 5 Maple Street $123,450 February 15 1 Center Street $100,000 February 23 2 Vista Drive $145,320 March 15 205 Rodeo Circle $389,100 FIGURE 7-2 Real Estate Sales for First Quarter of Year Figure 7-3 shows the output of a program that displays the total sales for the quarter year, with a subtotal for each month. FIGURE 7-3 Output of Example 3 A program to produce the output of Figure 7-3 must calculate a subtotal at the end of each month. The variable holding the month triggers a subtotal whenever its value changes. Such a variable is called a control variable and each change of its value is called a break. EXAMPLE 3 The following program produces the output of Figure 7-2. The data of Figure 7-2 are stored in the sequential file HOMESALE.TXT. The program allows for months with no sales. Because monthly subtotals will be printed, the month-of-sale field is an appropriate control variable. Private Sub cmdCreateReport_Click() Dim currentMonth As String, newMonth As String Dim dayNum As Integer, address As String Dim price As Single, monthTotal As Single Dim yearTotal As Single, doneFlag As Boolean ‘Display home sales by month picReport.Cls Open “HOMESALE.TXT” For Input As #1 currentMonth = “” ‘Name of month being subtotaled monthTotal = 0 yearTotal = 0 doneFlag = False ‘Flag to indicate end of list Do While Not doneFlag Using Sequential Files 227
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Computer Programming Concepts and V
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CONTENTS SECTION 1: PROBLEM SOLVING
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13.3 WEB PAGE PROGRAMMING WITH VBSC
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S E C T I O N 1 PROBLEM SOLVING
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4 Computer Programming Concepts and
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10 Computer Programming Concepts an
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S E C T I O N 2 FUNDAMENTALS OF PRO
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3.1 SUB PROCEDURES, PART I Structur
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The second task performed by the ad
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‘The density (number of people pe
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"Hawaii", 1184000, 6471 "Alaska", 6
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dure by just using the variable in
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Call CalculateSum(x, y, s) Call Dis
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■ FORM-LEVEL VARIABLES Visual Bas
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3. In Appendix D, the section “St
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Private Sub cmdDetermine_Click() Di
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Private Sub cmdCompute_Click() Dim
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preceded with the word ByVal. Built
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It is clear from the hierarchy char
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The meaningful procedure names, alo
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FIGURE 3-9 Sample Run for Programmi
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4.1 RELATIONAL AND LOGICAL OPERATOR
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(a) (2 < n) And (n < 6) (b) (2 < n)
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SOLUTION: In the following program,
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The Else part of an If block can be
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picTax.Cls picTax.Print “Your FIC
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Case 4, 5 picOutcome.Print “You a
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EXAMPLE 3 The following program use
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Case Else picResult.Print “The st
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4. The items in the value list must
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The hierarchy chart in Figure 4-4 s
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‘Program to compute employees’
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Private Function TaxMarried(adjPay
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and tells us whether the food meets
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S E C T I O N 5 REPETITION
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132 Computer Programming Concepts a
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S E C T I O N 6 ARRAYS
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Page 223: S E C T I O N 7 SEQUENTIAL FILES
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10.1 LIST BOXES AND COMBO BOXES The
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Private Sub cmdAdd_Click() Dim item
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either typing in information or jus
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Private Sub cmdDisplay_Click() picF
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clicks on the square to toggle betw
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circle and the button is said to be
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hsbBar.Value changes accordingly. T
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THE SHAPE CONTROL The shape control
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FIGURE 10-9 A Picture Created with
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Rows 9 ScrollBars 0 - flexScrollBar
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Private Sub cmdQuit_Click() End End
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Here, the menu bar contains two men
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Clipboard.Clear deletes the content
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cedures that are available to all f
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The Flags property influences certa
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13. Additional forms serve as new w
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6. Voting Machine. The members of t
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11.1 AN INTRODUCTION TO DATABASES T
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9. Click on the down arrow to the r
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clicked or a Move, Update, Delete,
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Do While (Not foundFlag) And (Not d
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mary key. Databases of student enro
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question mark stands for a single c
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1995 populations. When the second c
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If a Find method does not locate a
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place an x in the check box next to
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population (in descending order). W
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Creating and Designing Databases 34
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9. When all fields have been specif
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Creating and Designing Databases 34
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TABLE 11.5(B) TABLE 11.5(C) course
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(a) Update the quantity field of th
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12.1 CLASSES AND OBJECTS noun A wor
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Task Statement Assign a value to a
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EXAMPLE 1 and then an instance of t
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[Run, enter the data for a student
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SOLUTION: Object Property Setting f
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4. Methods can be either Function o
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‘Student Class (CStudent) Private
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txtFinal.Text = “” picGrades.Pr
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■ EVENTS In the previous section
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frmCircles.ForeColor = vbRed ‘Mak
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Public Function X() As Integer X =
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End Sub Private Sub cmdDropBomb_Cli
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Next i End Sub Public Function Read
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Remove method. The number of object
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S E C T I O N 13 COMMUNICATING WITH
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A P P E N D I C E S
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APPENDIX C VISUAL BASIC STATEMENTS,
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CANCEL The Cancel property provides
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COLS and ROWS The Cols and Rows pro
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DEFINT, DEFLNG, DEFSNG, DEFDBL, DEF
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ENVIRON Visual Basic has an environ
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FONT.ITALIC or FONTITALIC These pro
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yields “1234.”, Format(1234000,
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the length of the string currently
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ISNUMERIC The value of the function
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Unlock statement is used to remove
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Focus Default Default Number First
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OR (Logical Operator) The logical e
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the same as in the original Dimensi
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SECOND The function Second extracts
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STRETCH When the Stretch property o
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UNLOCK The Unlock command is intend
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[COLOR]: Numbers written in base 16
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Appendix D 457
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466 Technology of the Internet D Da
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468 Technology of the Internet Rela
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470 Technology of the Internet 2. D
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SYSTEM REQUIREMENTS CD-ROM INSTRUCT
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Computer Programming Concepts and Visual Basic David I. Schneider

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