Computer Programming Concepts and Visual Basic David I. Schneider

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176 Computer Programming Concepts and Visual Basic [Run and click the command button.] ■ PASSING ARRAYS BETWEEN PROCEDURES An array that is not dimensioned in the (Declarations) section of (General) but rather is declared in a procedure is local to that procedure and unknown in all other procedures. However, an entire local array can be passed to another procedure. The name of the array, followed by an empty set of parentheses, must appear as an argument in the calling statement, and an array variable name of the same type must appear as a corresponding parameter in the procedure definition of the procedure that is to receive the array. EXAMPLE 4 The following program illustrates passing an array to both a Sub procedure and a Function procedure. Private Sub cmdDisplayAverage_Click() ‘Pass array to Sub procedure and Function procedure Dim score(1 To 10) As Integer Call FillArray(score()) picAverage.Cls picAverage.Print “The average score is”; Sum(score()) / 10 End Sub Private Sub FillArray(s() As Integer) ‘Fill array with scores s(1) = 85 s(2) = 92 s(3) = 75 s(4) = 68 s(5) = 84 s(6) = 86 s(7) = 94 s(8) = 74 s(9) = 79 s(10) = 88 End Sub] Private Function Sum(s() As Integer) As Integer Dim total As Integer, index As Integer ‘Add up scores total = 0 For index = 1 To 10 total = total + s(index) Next index Sum = total End Function [Run and click the command button.]
Sometimes it is also necessary to pass a form-level array from one procedure to another. For example, you might have a sorting procedure (discussed in Section 6.3) and three form-level arrays to be sorted. The sorting procedure would be called three times, each time passing a different form-level array. The method for passing a form-level array to another procedure is the same as the method for passing a local array. EXAMPLE 5 The following program incorporates all three topics discussed in this section. It reads ordered lists of computer languages and spoken languages into form-level arrays, requests a new language as input, and inserts the language into its proper array position (avoiding duplication). The language arrays are dimensioned to hold up to 20 names; the variables numCompLangs and numSpokLangs record the actual number of languages in each of the ordered arrays. The original contents of the data files are COMPLANG.TXT:ADA, C, Cobol, Fortran, Pascal, Visual Basic SPOKLANG.TXT:Cantonese, English, French, Mandarin, Russian, Spanish Object Property Setting frmAdding Caption Adding to an Ordered Array lblNew Caption New language: txtLang Text (blank) cmdAddComp Caption Add to Computer List cmdAddSpok Caption Add to Spoken List picAllLang Dim compLang(1 To 20) As String Dim spokLang(1 To 20) As String Dim numCompLangs As IntegerDim numSpokLangs As Integer Private Sub AddALang(lang() As String, langCount As Integer) Dim language As String, n As Integer, i As Integer ‘Insert a language into an ordered array of languages language = Trim(txtLang.Text) n = 0 Do n = n + 1 Loop Until (UCase(lang(n))>= UCase(language)) Or (n = langCount) If UCase(lang(n)) < UCase(language) Then ‘Insert new language at end lang(langCount + 1) = language langCount = langCount + 1 ElseIf UCase(lang(n)) > UCase(language) Then ‘Insert before item n For i = langCount To n Step -1 lang(i + 1) = lang(i) Next i lang(n) = language langCount = langCount + 1 End If End Sub Private Sub cmdAddComp_Click() ‘Insert language into ordered array of computer languages Call AddALang(compLang(), numCompLangs) Call DisplayArray(compLang(), numCompLangs) End Sub Private Sub cmdAddSpok_Click() ‘Insert language into ordered array of spoken languages Call AddALang(spokLang(), numSpokLangs) Using Arrays 177
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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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226 Computer Programming Concepts a
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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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