Computer Programming Concepts and Visual Basic David I. Schneider

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118 Computer Programming Concepts and Visual Basic EXAMPLE 7 Select Case is useful in defining functions that are not determined by a formula. The following program assumes the current year is not a leap year. Object Property Setting frm5_3_7 Caption Seasons lblSeason Caption Season txtSeason Text (blank) cmdNumber Caption Number of Days picNumDays Private Sub cmdNumber_Click() Dim season As String ‘Determine the number of days in a season picNumDays.Cls season = txtSeason.Text picNumDays.Print season; “ has”; NumDays(season); “days.” End Sub Private Function NumDays(season As String) As Integer ‘Look up the number of days in a given season Select Case UCase(season) Case “WINTER” NumDays = 87 Case “SPRING” NumDays = 92 Case “SUMMER”, “AUTUMN”, “FALL” NumDays = 93 End Select End Function [Run, type Summer into the text box, and press the command button.] COMMENTS 1. Some programming languages do not allow a value to appear in two different value lists; Visual Basic does. If the value of the selector appears in two different value lists, the action associated with the first value list will be carried out. 2. In Visual Basic, if the value of the selector does not appear in any of the value lists and there is no Case Else clause, execution of the program will continue with the statement following the Select Case block. 3. The Case statements and their actions do not have to be indented; however, because indenting improves the readability of the block, it is regarded as good programming style. As soon as you see the words Select Case, your eyes can easily scan down the block to find the matching End Select statement. You immediately know the number of different cases under consideration.
4. The items in the value list must evaluate to a constant of the same type, string or numeric, as the selector. For instance, if the selector evaluates to a string value, as in Dim firstName A String firstName = txtBox.Text Select Case first Name then the clause Case Len(firstNme) would be meaningless. 5. If the word Is, which should precede an inequality sign in a value list, is accidentally omitted, the smart editor will automatically insert it when checking the line. 6. A Case clause of the form Case b To c selects values from b to c inclusive. However, the extreme values can be excluded by placing the action inside an If block beginning with If (selector b) And (selector c) Then. 7. The value of b must be less than or equal to the value of c in a Case clause of the form Case b To c. 8. Every Select Case block can be replaced by an If block. Select Case is preferable to an If block when the possible choices have more or less the same importance. 9. In Appendix D, the section “Stepping Through Programs Containing Selection Structures: Section 4” uses the Visual Basic debugging tools to trace the flow through a Select Case block. 4.4 A CASE STUDY: WEEKLY PAYROLL This case study processes a weekly payroll using the 1998 Employer’s Tax Guide. Table 4.2 shows typical data used by a company’s payroll office. These data are processed to produce the information in Table 4.3 that is supplied to each employee along with his or her paycheck. The program should request the data from Table 4.2 for an individual as input and produce output similar to that in Table 4.3. The items in Table 4.3 should be calculated as follows: Current Earnings: Hourly wage times hours worked (with time-and-a-half after 40 hours) Year-to-Date Earnings: Previous year-to-date earnings plus current earnings FICA Tax: Sum of 6.2 percent of first $68,400 of earnings (Social Security benefits tax) and 1.45 percent of total wages (Medicare tax) Federal Income Tax Withheld: Subtract $51.92 from the current earnings for each withholding exemption and use Table 4.4 or Table 4.5, depending on marital status Check Amount: [Current earnings] – [FICA taxes] – [Income tax withheld] TABLE 4.2 Employee Data A Case Study: Weekly Payroll 119 Previous Hourly Hours Withholding Marital Year-to-Date Name Wage Worked Exemptions Status Earnings Al Clark $45.50 38 4 Married $68,925.50 Ann Miller $44.00 35 3 Married $68,200.00 John Smith $17.95 50 1 Single $30,604.75 Sue Taylor $25.50 43 2 Single $36,295.50
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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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Page 91 and 92: Call CalculateSum(x, y, s) Call Dis
Page 93 and 94: ■ FORM-LEVEL VARIABLES Visual Bas
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Page 119 and 120: picTax.Cls picTax.Print “Your FIC
Page 121 and 122: Case 4, 5 picOutcome.Print “You a
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Page 167: S E C T I O N 6 ARRAYS
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168 Computer Programming Concepts a
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S E C T I O N 7 SEQUENTIAL FILES
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S E C T I O N 8 RANDOM-ACCESS FILES
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S E C T I O N 9 THE GRAPHICAL DISPL
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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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