VISUAL BASIC for beginners
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Thread: VISUAL BASIC for beginners

  1. #1
    Member
    Join Date
    Jun 2002
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    Post VISUAL BASIC for beginners

    First of all, i wanted to say that i didnt write this tutorial. Srill, it helped me and im hoping it will help other people too.
    Second, you can download VB 5.0 and other versions free at, http://msdn.microsoft.com/vbasic/dow...sualBasic5.asp


    Lesson1 :Introduction
    1.1 A brief description of Visual Basic
    VISUAL BASIC is a high level programming language evolved from the earlier DOS version called BASIC. BASIC means Beginners' Allpurpose Symbolic Instruction Code. It is a fairly easy programming language to learn. The codes look a bit like English Language. Different software companies produced different version of BASIC, such as Microsoft QBASIC, QUICKBASIC, GWBASIC ,IBM BASICA and so on.
    VISUAL BASIC is a VISUAL and events driven Programming Language.These are the main divergence from the old BASIC. In BASIC, programming is done in a text-only environment and the prgram is executed sequentially. In VISUAL BASIC, programming is done in a graphical environment. Because users may click on a certain object randomly, so each object has to be programmed indepently to be able to response to those actions(events).Therefore, a VISUAL BASIC Program is made up of many subprograms, each has its own program codes, and each can be excecuted indepently and at the same time each can be linked together in one way or another.
    1.2 The Visual Basic Environment
    On start up, Visual Basic 6.0 will display the following dialog box as shown in figure 1.1.
    You can choose to start a new project, open an existing project or select a list of recently opened programs. A project is a collection of files that make up your application. There are various types of applications we could create, however, we shall concentrate on creating Standard EXE programs(EXE means executable program). Now, click on the Standard EXE icon to go into the actual VB programming environment.

    The Blank Form window which you can design your application's interface.
    The Project window displays the files that are created in your application.
    The Properties window which displays the properties of various controls and objects that are created in your applications.
    It also includes a Toolbox that consists of all the controls essential for developing a VB Application. Controls are tools such as boxes, buttons, labels and other objects draw on a form to get input or display output. They also add visual appeal.


    Lesson 2.

    2.1 Creating Your First Application
    In this section, we are not going into the technical aspect of VB programming, just have a feel of it. Now, you can try out the examples below:
    Example 2.1.1 is a simple program . First of all, you have to launch Microsoft Visual Basic. Normally, a default form Form1 will be available for you to start your new project. Now, double click on form1, the source code window for form1 will appear. Don't worry about the begining and the end statements(i.e Private Sub Form_Load.......End Sub.); Just key in the lines in between the above two statements exactly as are shown here.When you run the program, you will be surprise that nothing shown up.In order to display the output of the program, you have to add the Form1.show statement like in Example 21.2 and Example 2.1.3. Try them out.
    Example 2.1.1
    Private Sub Form_Load
    For i=1 to 5
    print "Hello"
    next i
    End Sub Example 2.1.2
    Private Sub Form_Load
    Form1.show
    For i=1 to 5
    print "Hello"
    next i
    End Sub Example 2.1.3
    Private Sub Form_Load
    Form1.show
    For i=1 to10
    print i
    next i
    End Sub
    2.2 Steps in Building a Visual Basic Application
    Step 1 Draw the interface
    Step 2 Set Properties
    Step 3 Write the events code
    Example 2.1
    This program is a simple program that calculate the volume of a cylinder. Let design the interface:

    First of all, go to the properties window and change the form caption to Volume Of Cylinder. Then draw three label boxes and change their captions to Base Radius, height andvolume respectively. After that, draw three Text Boxes and clear its text contents so that you get three empty boxes. Named the text boxes asradius ,hght(we cannot use height as it is the built-in control name of VB)and volume respectively. Lastly, insert a command button and change its caption toO.K. and its name to OK. Now save the project as cylinder.vbp and the form as cylinder.vbp as well. We shall leave out the codes at the moment which you shall learn it in lesson3.
    Example 2.2
    Designing an attractive and user friendly interface should be the first step in constructing a VB program. To illustrate, let's look at the calculator program.
    >
    Now, please follow the following steps to design the calculator interface.
    Resize the form until you get the size you are satisfed with.
    Go to the properties window and change the default caption to the caption you want , such as 32 Calculator-----Designed by Vkliew.
    Change other properties of the form, such as background color, foreground color , border style.I recommend you set the following properties for Form1 for this calculator program:

    BorderStyle Fixed Single
    MaxButton False
    minButton True
    These properties will ensure that the users cannot resize or maximize your calculator
    window, but able to minimize the window.
    Draw the Display Panel by clicking on the Label button and and place your mouse on the form. Start drawing by pressing down your mouse button and drag it along.
    Click on the panel and the corresponding properties window will appear. Clear the default label so that the caption is blank(because the display panel is supposed to show the number as we click on the number button). It is good to set the background color to a bright color while the foreground color should be something like black..(for easy viewing). Change the name to display as I am going to use it later to write codes for the calculator.
    Now draw the command buttons that are necessary to operate a calculator. I suggest you follow exactly what is shown in the image above.
    Test run the project by pressing F5. If you are satisfied with the appearance, go ahead to save the project. At the same time, you should also save the file that contain your form.
    Now, I know you are very keen to know how to write the code so that the calculator is working.
    Please refer to my sample VB programs for the source codes.


    Lesson 3

    Now we shall attempt to write the codes for the cylinder program.
    Now, doubleclick on the O.K button and enter the codes between Private Sub OK_Click( ) and End Sub
    Private Sub OK_Click( )
    r = Val(radius.Text)
    h = Val(hght.Text)
    pi = 22 / 7
    v = pi * (r ^ 2) * h
    volume.Text= Str$(v)
    End Sub
    when you run the program , you should be able to see the interface as shown above. if you enter a value each in the radius box and the height box, then click OK, the value of of the Volume will be displayed in the volume box.
    I shall attempt to explain the above source program to newcomers in Visual Basic( If you are a veteran, you can skip this part) . Let me describe the steps using pseudocodes as follows:
    Procedure for clicking the OK button to calculate the volume of cylinder
    get the value of r from the radius text box
    get the value of h from the height text box
    assign a constant value 22/7 to pi
    calculate the volume using formula
    output the results to the Volume text box
    End of Procedure

    The syntax radius.Text consists of two parts, radius is the name of text box while Text is the textual contents of the text box. Generally, the syntax is: Object.Property
    In our example, the objects are radius, hght and volume, each having text as their property.Object and property is separated by a period(or dot).The contents of a text box can only be displayed in textual form, or in programming term,as string. To convert the contents of a text box to a numeric value so that mathematical operations can be performed , you have to use the function Val. Finally, In order to display the results in a text box, we have to perform the reverse procedure, that is, to convert the numeric value back to the textual form, using the function Str$.
    I shall also explain the syntax that defines the sub procedure Private Sub OK_click. Private Sub here means that the parameters , values and formulas that are used here belong only to the OK subprocedure(an object by itself).They cannot be used by other sub procedures or modules. OK_Click defines what kind of action the subprocedure OK will response .Here, the action is mouse click. There are other kind of actions like keypress, keyup, keydown and etc that I am going to due with in other lessons.
    Lesson 4

    Before writing an event procedure for a control to response to a user's action, you have to set certain properties for the control to determine its appearance and how it will work with the event procedure. You can set the properties of the controls in the properties windows. I am not going into the details on how to set the properties. However, I would like to stress a few important points about setting up the properties.
    You should set the Caption Property of a control clearly so that a user know what to do with that command. For example, in the calculator program, all the captions of the command buttons such as +, - , MC ,MR are commonly found in an ordinary calculator, a user should have no problem in manipulating the buttons.
    You should set a meaningful name for the Name Property because it is easier for you to write and read the event procedure and easier to debug your program later.
    Another property that is important is whether you want your control to be visible or not at start up.This property can only set to be true or false.
    One more important property is whether the control is enabled or not.

    Before writing an event procedure for a control to response to a user's action, you have to set certain properties for the control to determine its appearance and how it will work with the event procedure. You can set the properties of the controls in the properties windows. I am not going into the details on how to set the properties. However, I would like to stress a few important points about setting up the properties.
    You should set the Caption Property of a control clearly so that a user know what to do with that command. For example, in the calculator program, all the captions of the command buttons such as +, - , MC ,MR are commonly found in an ordinary calculator, a user should have no problem in manipulating the buttons.
    You should set a meaningful name for the Name Property because it is easier for you to write and read the event procedure and easier to debug your program later.
    Another property that is important is whether you want your control to be visible or not at start up.This property can only set to be true or false.
    One more important property is whether the control is enabled or not.

    Lesson 5
    There are many types of data we come across in our daily life. For example, we need to handle data such as names, adresses, money, date, stock quotes, statistics and etc everyday. Similarly In Visual Basic, we are also going to deal with these kinds of data. However, to be more systematic, VB divides data into different types.
    5.1 Types of Visual Basic Data
    5.1.1 Numeric Data
    Numeric data are data that consists of numbers, which can be computed mathematically with various standard operators such as add, minus, multiply, divide and so on. In Visual Basic, the numeric data are divided into 7 types, they are summarised in Table 6.1
    Table 5.1: Numeric Data Types

    Type Storage Range of Values
    Byte 1 byte 0 to 255
    Integer 2 bytes -32,768 to 32,767
    Long 4 bytes -2,147,483,648 to 2,147,483,648
    Single 4 bytes -3.402823E+38 to -1.401298E-45 for negative values
    1.401298E-45 to 3.402823E+38 for positive values.
    Double 8 bytes -1.79769313486232e+308 to -4.94065645841247E-324 for negative values
    4.94065645841247E-324 to 1.79769313486232e+308 for positive values.
    Currency 8 bytes -922,337,203,685,477.5808 to 922,337,203,685,477.5807
    Decimal 12 bytes +/- 79,228,162,514,264,337,593,543,950,335 if no decimal is use
    +/- 7.9228162514264337593543950335 (28 decimal places).
    5.1.2 Nonmeric Data Types
    the nonnumeric data types are summarised in Table 5.2
    Table 5.2: Nonnumeric Data Types

    Data Type Storage Range
    String(fixed length) Length of string 1 to 65,400 characters
    String(variable length) Length + 10 bytes 0 to 2 billion characters
    Date 8 bytes January 1, 100 to December 31, 9999
    Boolean 2 bytes True or False
    Object 4 bytes Any embedded object
    Variant(numeric) 16 bytes Any value as large as Double
    Variant(text) Length+22 bytes Same as variable-length string
    5.1.3 Suffixes for Literals
    Literals are values that you assign to a data. In some cases, we need to add a suffix behind a literal so that VB can handle the calculation more accurately. For example, we can use num=1.3089# for a Double type data. Some of the suffixes are displayed in Table 5.3.
    Table 5.3

    Suffix Data Type
    & Long
    ! Single
    # Double
    @ Currency
    In additon, we need to enclose string literals within two quotations and date and time literals within two # sign. Strings can contain any characters, including numbers. The following are few examples:
    memberName="Turban, John."
    TelNumber="1800-900-888-777"
    LastDay=#31-Dec-00#
    ExpTime=#12:00 am#
    5.2 Managing Variables
    Variables are like mail boxes in the post office. The contents of the variables changes every now and then, just like the mail boxes. In term of VB, variables are areas allocated by the computer memory to hold data. Like the mail boxes, each variable must be given a name. To name a variable in Visual Basic, you have to follow a set of rules.
    5.2.1 Variable Names
    The following are the rules when naming the variables in Visual Basic
    It must be less than 255 characters
    No spacing is allowed
    It must not begin with a number
    Period is not permitted
    Examples of valid and invalid variable names are displayed in Table 5.4
    Table 5.4
    Valid Name Invalid Name
    My_Car My.Car
    ThisYear 1NewBoy
    Long_Name_Can_beUSE He&HisFather *& is not acceptable


    5.2.2 Declaring Variables
    In Visual Basic, one needs to declare the variables before using them by assigning names and data types. They are normally declared in the genaral section of the codes' windows using the Dim statement.
    The format is as follows:
    Dim variableNmae as DataType
    Example 5.1
    Dim password As String
    Dim yourName As String
    Dim firstnum As Integer
    Dim secondnum As Integer
    Dim total As Integer
    Dim doDate As Date
    You may also combine them in one line , separating each variable with a comma, as follows:
    Dim password As String, yourName As String, firstnum As Integer,.............
    If data type is not specified, VB will automatically declares the variable as a Variant.
    For string declaration, there are two possible format, one for the variable-length string and another for the fixed-length string. For the variable-length string, just use the same format as example 5.1 above. However, for the fixed-length string, you have to use the format as shown below:
    Dim VariableName as String * n, where n definex the number of characters the string can hold.
    Example 5.2:
    Dim yourName as String * 10
    yourName can holds no more than 10 Characters.
    Lesson 6
    6.1 Assigning Values to Variables
    After declaring various variables using the Dim statements, we can assign values to those variables.
    The general format of an assignment is
    Variable=Expression
    The variable can be a declared variable or a control property value. The expression could be a mathematical expression, a number, a string, a boolean value(true or false) and etc. The following are some examples:
    firstNumber=100
    secondNumber=firstNumber-99
    userName="John Lyan"
    userpass.Text = password
    Label1.Visible = True
    Command1.Visible = false
    Label4.Caption = textbox1.Text
    ThirdNumber = Val(usernum1.Text)
    total = firstNumber + secondNumber+ThirdNumber

    6.2 Operators in Visual Basic
    In order to compute inputs from users and to generate results, we need to use various mathematical
    operators. In Visual Basic, except for + and -, the symbols for the operators are different from normal mathematical operators,as shown in Table 6.1.
    Table 6.1

    Operator Mathematical function Example
    ^ Exponential 2^4=16
    * Multiplication 4*3=12
    / Division 12/4=3
    Mod Modulus(return the remainder from an integer division) 15 Mod 4=3
    \ Integer Division(discards the decimal places) 19\4=4
    + or & String concatenation "Visual"&"Basic"="Visual Basic"


    Example 6.1:
    firstName=Text1.Text
    secondName=Text2.Text
    yourName=firstName+secondName
    number1=val(Text3.Text)
    number2=val(Text4.Text)
    number3=num1*(num2^3)
    number4=number3 Mod 2
    number5=number4\number1
    Total=number1+number2+number3+number4+number5
    Average=Total/5


    I am working on the second half of this tutorial it will be posted soon. People with experience with Visual Basic please post suggestions and opinions, thank you.

  2. #2
    AntiOnline Newbie
    Join Date
    Jun 2002
    Posts
    47
    thank for the info. i am just getting into the programming thing and started with VB 6. to tell the truth i just started this week. God help.

    greenies for you.


    wortcraft

  3. #3

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