Computer Programming Concepts and Visual Basic David I. Schneider

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200 Computer Programming Concepts and Visual Basic Dim amount As Single, nutWid As Single ‘Display amount of each component picAnalysis.Cls picAnalysis.Print “This meal contains the” picAnalysis.Print “following quantities” picAnalysis.Print “of these nutritional” picAnalysis.Print “components:” picAnalysis.Print For col = 1 To 5 amount = 0 For row = 1 To 10 amount = amount + quantity(row) * nutTable(row, col) Next row picAnalysis.Print nutName(col) & “:”; Tab(16); amount Next col End Sub [Run, type the following quantities into each text box, and click the command button.] COMMENT 1. We can define three- (or higher-) dimensional arrays much as we do two-dimensional arrays. A three-dimensional array uses three subscripts, and the assignment of values requires a triple-nested loop. As an example, a meteorologist might use a three-dimensional array to record temperatures for various dates, times, and elevations. The array might be created by the statement Dim temps(1 To 31, 1 To 24, 0 To 14) As Single 6.6 A CASE STUDY: CALCULATING WITH A SPREADSHEET Spreadsheets are one of the most popular types of software used on personal computers. A spreadsheet is a financial planning tool in which data are analyzed in a table of rows and columns. Some of the items are entered by the user. Other items, often totals and balances, are calculated using the entered data. The outstanding feature of electronic spreadsheets is their ability to recalculate an entire table after changes are made in some of the entered data, thereby allowing the user to determine the financial implications of various alternatives. This is called “What if?” analysis.
■ THE DESIGN OF THE PROGRAM Figure 6-9 contains an example of a spreadsheet used to analyze a student’s financial projections for the four quarters of a year. Column F holds the sum of the entries in columns B through E, rows 6 and 14 hold sums of the entries in rows 3 through 5 and 9 through 13, respectively, and row 16 holds the differences of the entries in rows 6 and 14. Because the total balance is negative, some of the amounts in the spreadsheet must be changed and the totals and balances recalculated. A B C D E F 1 Fall Winter Spring Summer Total 2 Income 3 Job 1000 1300 1000 2000 5300 4 Parents 200 200 200 0 600 5 Scholarship 150 150 150 0 450 6 Total 1350 1650 1350 2000 6350 7 8 Expenses 9 Tuition 400 0 400 0 800 10 Food 650 650 650 650 2600 11 Rent 600 600 600 400 2200 12 Books 110 0 120 0 230 13 Misc 230 210 300 120 860 14 Total 1990 1460 2070 1170 6690 15 16 Balance –640 190 –720 830 –340 FIGURE 6-9 Spreadsheet for Student’s Financial Projections The 96 locations in the spreadsheet that hold information are called cells. Each cell is identified by its row number and column letter. For instance, cell 14, C contains the amount 1460. For programming purposes, each column is identified by a number, starting with 1 for the leftmost column. Thus cell 14, C will be cell 14, 3 in our program. This case study develops a program to produce a spreadsheet with the five columns of numbers shown in Figure 6-11, three user-specified categories of income, and five user-specified categories of expenses. The following tasks are to be selected by command buttons: 1. Start a new spreadsheet. All current category names and values are erased and the cursor is placed in the text box of the first income category. 2. Quit. Three additional tasks need to be performed as the result of other events: 1. Create the spreadsheet when the form is loaded. 2. Limit the user to editing category names and quarterly values. 3. Display totals after a change is made in the spreadsheet. ■ THE USER INTERFACE A Case Study: Calculating with a Spreadsheet 201 Each cell in the spreadsheet will be an element of a text box control array. A control array of labels is needed for the numeric labels to the left of each row and another control array of labels for the alphabetic labels at the top of each column. Finally, two command buttons are required. The task of controlling which cells the user can edit will be handled by a GotFocus event. The task of updating the totals will be handled by a LostFocus event. Figure 6-10 shows one possible form design with all control elements loaded. For this application of a spreadsheet, the headings that have been assigned to cells in rows 1, 2, 6, 8, 14, and 16 are fixed; the user will not be allowed to edit them. The other entries in column A, the category names, may be edited by the user, but we have provided the set from Figure 6-9 as the default.
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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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Page 158 and 159: 150 Computer Programming Concepts a
Page 167: S E C T I O N 6 ARRAYS
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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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