Computer Programming Concepts and Visual Basic David I. Schneider

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18 Computer Programming Concepts and Visual Basic Double-click the Standard EXE icon to bring up the initial Visual Basic screen in Figure 2-2. The appearance of this screen varies slightly with the different versions of Visual Basic. FIGURE 2-2 The Initial Visual Basic Screen The Menu bar of the Visual Basic screen displays the commands you use to work with Visual Basic. Some of the menus, like File, Edit, View, and Window, are common to most Windows applications. Others, such as Project, Format, and Debug, provide commands specific to programming in Visual Basic. The Toolbar is a collection of icons that carry out standard operations when clicked. For example, the fifth icon, which looks like a diskette, can be used to save the current program to a disk. To reveal the function of a Toolbar icon, position the mouse pointer over the icon for a few seconds. The large stippled Form window, or form for short, becomes a Windows window when a program is executed. Most information displayed by the program appears on the form. The information usually is displayed in controls that have been placed on the form. The Form Layout window allows you to position the location of the form at run time relative to the entire screen using a small graphical representation of the screen. The Project Explorer window is seldom needed for our purposes until Section 12. The Properties window is used to change how objects look and react. The icons in the Toolbox represent controls that can be placed on the form. The four controls discussed in this section are text boxes, labels, command buttons, and picture boxes. Text boxes: You use a text box primarily to get information, referred to as input, from the user. Labels: You place a label to the left of a text box to tell the user what type of information to enter into the text box. You also use labels to display output. Command buttons: The user clicks a command button to initiate an action. Picture boxes: You use a picture box to display text or graphics output.
A TEXT BOX WALKTHROUGH 1. Double-click on the text box icon. (The text box icon consists of the letters ab and a vertical bar cursor inside a rectangle and is the fourth icon in the Toolbox.) A rectangle with eight small squares, called sizing handles, appears at the center of the form. See Figure 2-3. FIGURE 2-3 A Text Box with Sizing Handles 2. Click anywhere on the form outside the rectangle to remove the handles. 3. Click on the rectangle to restore the handles. An object showing its handles is (said to be) selected. A selected object can have its size altered, location changed, and other properties modified. 4. Move the mouse arrow to the handle in the center of the right side of the text box. The cursor should change to a double arrow ( ). Hold down the left mouse button, and move the mouse to the right. The text box is stretched to the right. Similarly, grabbing the text box by one of the other handles and moving the mouse stretches the text box in another direction. For instance, you use the handle in the upper-left corner to stretch the text box up and to the left. Handles also can be used to make the text box smaller. 5. Move the mouse arrow to any point of the text box other than a handle, hold down the left mouse button, and move the mouse. You can now drag the text box to a new location. Using Steps 4 and 5, you can place a text box of any size anywhere on the form. Note: The text box should now be selected; that is, its sizing handles should be showing. If not, click anywhere inside the text box to select it. 6. Press the delete key, Del, to remove the text box from the form. Step 7 gives an alternative way to place a text box of any size at any location on the form. 7. Click on the text box icon in the Toolbox. Then move the mouse pointer to any place on the form. (When over the form, the mouse pointer becomes a pair of crossed thin lines.) Hold down the left mouse button, and move the mouse on a diagonal to generate a rectangle. Release the mouse button to obtain a selected text box. You can now alter the size and location as before. Note: The text box should now be selected; that is, its sizing handles should be showing. If not, click anywhere inside the text box to select it. 8. Press F4 to activate the Properties window. (You can also activate the properties window by clicking on it or clicking on the Properties window icon in the Toolbar.) See Figure 2-4. The first line of the Properties window (called the Object box) reads “Text1 TextBox”. Text1 is the current name of the text box. The two tabs permit you to view the list of properties either alphabetically or grouped into categories. Text boxes have 43 properties that can be grouped into 7 categories. Use the up- and down-arrow keys (or the up- and down-scroll arrows) to glance through the list. The left column gives the property and the right column gives the current setting of the property. We discuss four properties in this walkthrough. Visual Basic Objects 19
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70 Computer Programming Concepts an
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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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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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