Introduction to the Visual Basic Language
The Visual Basic Language in Microsoft Visual Basic
Microsoft Visual Basic is not just a production environment. It also includes a fully functional language that can stand on its own. The language started as Basic, then QuickBasic or QBasic. It first went through various changes. In 2002, Microsoft created a new serious language that can understand and use the .NET Framework. Microsoft Visual Basic is used to create graphical applications, also referred to as Graphical User Interface (GUI) applications, web-based applications, and other types of applications. In order to effectively create these applications, you must be familiar with the language used in this programming environment.
In our lessons, we are going to study the language that serves as a foundation to the Microsoft Visual Basic programming environment.
The primary job of an application is to show its results on the monitor. A console application is one that displays its results in a black window referred to as a DOS window. In some of our lessons, we will create those types of applications. The Visual Basic language provides a rectangular object called a message box. If you create a Visual Basic application, you can display the results in a message box. That's what we will use in most of our lessons.
To create an application, you start with a project. There are two main ways you can create a Visual Basic project. You can use a text editor or a programming environment.
To create a program, you write the necessary instructions in a text-based document. This is called a source file. A source file that contains Visual Basic instructions is a regular, simple, ASCII, text-based file. It has the extension .vb as a Windows file.
In Visual Basic source file, you write code as we will learn throughout our lessons. The code that is conform to the Visual Basic language is included in a section known as the module. This section starts with the Module keyword followed by a name and ends with the End Module expression. Everything between the line that has Module and the line that has End Module belongs to the same entity. Based on this, a simple file in Visual Basic would have the following:
Module ModuleName End Module
A procedure is a section of code that takes care of a specific task. In a module, the basic formula of a procedure is:
Sub ProcedureName() End Sub
Notice that it ends with the End Sub line. Because a module holds the code of a Visual Basic program, a procedure is included inside the start and the end of the module section. This would be done as follows:
Module ModuleName Sub ProcedureName() End Sub End Module
We will come back to procedures in another lesson. For now, the most fundamental procedure used in Visual Basic is called Main. In a program, the Main procedure is the entry point. That is where the program starts.
Another common procedure highly used in Visual Basic is called MsgBox. As its name indicates, the MsgBox procedure is used to display a message in a dialog box. To make this happen, you can include the message inside the parentheses of MsgBox. The message itself should be included in double-quotes. An example would be:
To distinguish a procedure from other items used in a program, we will sometimes write it followed by parentheses. Examples are Main() and MsgBox().
The MsgBox() procedure provides more details. We will come back to it in Lesson 7.
As mentioned already, you write the instructions of your project in English. But the computer doesn't understant it. The instructions must be translated in a language the computer can understand. That language is called machine language. To translate the instructions from English to machine dialect, you use a program named a compiler. In reality, a compiler is a group of sub-programs that accomplish various goals to get a functional program at the end. The end result is a program that can be executed in a computer other than the one you used to create the project. That final program is called an executable.
Ae mentioned already, a compiler is a computer program made of internal other sub-programs. One of the sub-programs, in fact probably the first, of a compiler is called a parser. A parser "scans" a file that contains (part of) the program. It checks the syntax, keywords, unknown words, and some other routines. If the parser finds a problem, which could be anything, either it stops or it continues making a list of the mistakes it found. Then it displays this list to you to fix. Sometimes it would point to the exact line where the/a problem was found. Sometimes it would point to the line where the problem showed its impact although the problem may be found somewhere else. With experience, you will know how to fix the programs or troubleshoot the problems.
If the parser doesn't find any problem, or after you have fixed the problems, it (the parser) passes its result(s) to the compiler. The compiler calls another program called a linker. If the program contains just one file, the linker considers it. If the program contains more than one file, the linker considers them. The linker gathers some of the files that the compiler shipped with (those files that your program needs in order to work), puts them together ("links" them) with your file(s) to get your instructions in a manner that can produce a suitable result. If there is no significant problem, the compiler creates the executable. This doesn't mean that everything is alright, it only means that the compiler thinks that everything is alright: it is still possible that the result may not be what you would expect. We will come back to these issues.
To make your life easier, all of the sub-programs (parser, linker, debugger, etc) that ship with Visual Basic are grouped in one large program: the compiler. Therefore, from now on, we will use the word "compiler" to refer to the program you use to translate your English instructions into a machine language.
Microsoft created and makes freely available a Visual Basic compiler you can use to create your applications. The Visual Basic compiler is named vbc. A compiler is primarily a computer program, that is an executable. As such, it uses to extension .exe. Therefore, the compiler we will use to create our program is called vbc.exe.
As mentioned already, the vbc.exe compiler is freely available. You can get it by downloading the .NET Framework from the Microsoft web site. Normally, you are likely to have the .NET Framework installed in your computer already. By default, it is installed in C:\Windows\Microsoft.NET\Framework\v4.0.21006.
You can use the vbc.exe to create programs from the Command Prompt. To do this, you can add the compiler's path to the Path of the Environment Variables. To start, use a file utility such as Windows Explorer and display the folder where vbc.exe is installed. Here is its path in Windows Explorer:
Select the path in the top combo box and copy it to the clipboard. Start the Control Panel. Click System and Security:
In the System and Security section, click System:
In the System window, click Change Settings. In the System Properties dialog box, click the Advanced tab. Click the Environment Variables button:
In the System Variables section, double-click Path or click it and click Edit:
Press the End key, type a semi-colon ";". Paste the value you had copied from the clipboard:
Click OK three times.
Open the Command Prompt. Type CD\ and press Enter to move to the root drive. Type CD and a space, followed by the folder (and sub-folder(s)) where the file is located, and press Enter. To compile, type vbc followed by the name of the file and its extension:
The file produced from this operation has the extension .exe. By default, it holds same name as the file you had used. If you want to get an executable using a name of your choice, after vbc, type /out: followed by the name you want, followed by a .exe extension, followed by a space, and followed by the name of the file you had created, with its extension. The formula to follow would be:
vbc /out:NameOfExecutate.exe Filename.vb
The NameOfExecutate represents the name you want the executable to have. If the name you want is in one word, you can just type it. Here is an example:
vbc /out:Welcome.exe Exercise.vb
If you want a name made of various words, you can include those words in double-quotes.
If you are creating your application using a text editor and if you create many files, when compiling the project, you must remember to reference each file. To do that, in the last section, add the name of each file with its extension:
vbc FileName1.vb FileName2.vb FileName_n.vb
The executable you get is the one you can use on other computers and that you can distribute to other people.
After building the code, you and your users can execute it. If you are working from the Command Prompt, to execute the project, type the name of the file that has the .exe extension and press Enter:
If you are working from Microsoft Visual C# 2010 Express or from Microsoft Visual Studio, to execute an application, on the main menu, you can click Debug -> Start Debugging.
Although you can creat a complete and fully functional application using a text editor, Microsoft Visual Studio and Microsoft Visual Basic 2010 Express provide a graphical environment that is more convenient. You start by creating a project. To create a project:
When you start a new application from the New Project dialog box, you are asked whether you want to create a new solution too, and you must give it a name. By default, the new project and solution would hold the same name. If you accept the suggestions, you would get a main folder with the name of the project. Inside of that folder, there would be a folder with the same name. That inside folder would represent the project.
After creating a solution, its name appears on the title bar of Microsoft Visual Studio. The name of the project would appear in the Solution Explorer.
The Solution Explorer is a window that displays a list of the files that make up a project. To access the Solution Explorer:
The Solution Explorer is made of four sections. Like every regular window, the Solution Explorer is equipped with a title bar that displays its name on the left side and three buttons on the right side:
Under its title bar, the second section of the Solution Explorer is a toolbar::
The third part of the Solution Explorer is its body. It shows the folders, files, and resources that are part of the current project. To expand a node, you can either click its button or double-click its name. To collapse a node, either click its button or double-click it.
The root of the list is the name of the solution. Under the root is the name of the current project. If the solution contains more than one project, the name of each project is represented under the solution. Inside of the project are its folders, files, and resources. The first item under a project name is References. After the References node, there are the names of the classes that are part of the project.
The fourth part of the Solution Explorer is its tab.
The Properties window shows the Windows operating system's details of the files or resources used in a project. To display it:
The display and rectangular behavior of the Properties window follows the description we had for the Solution Explorer.
To show the operating system's characteristics of a project or a file, in the Solution Explorer, click the object:
The Properties window displays different fields depending on the item selected in the Solution Explorer. You can change some things in the Properties window. When a field is disabled, it means you cannot modify it.
A solution is used to coordinate the different aspects of an application that is being created. When you have created a project, the name of the solution displays as the top node of the tree in the Solution Explorer:
The title bar of the studio displays the name of the solution in the left section:
If you start saving a project for the first time, it would bring the Save Project dialog box. By default, Microsoft Visual Studio selects your personal directory as the path to the solution. This is called the location. In the location, Microsoft Visual Studio creates a folder as the solution of the project. The solution must have, or must be stored, in its own folder. As mentioned earlier, Microsoft Visual Studio uses the name of the project as the name of the solution. To rename the solution, you can change the string in the Solution Name text box. Remember that you can enter the name of the project in the Name text box. Here is an example:
When you save a project (for the first time), by default, Microsoft Visual Studio creates a new folder for it in the Documents\Visual Studio 2010\Projects folder. It uses the name of the solution to name the folder. It creates some files and stores them in that new folder. Then, it creates a sub-folder, using the name of the project, inside of the folder of the solution. Besides the sub-folder with the name as the project, it creates another folder named debug. It also creates another folder named Debug in the sub-folder of the name of the project. In each folder and some other folders, it creates some files that we will not pay attention to for now.
If the project had already been saved but you want to change the name of the solution, on the main menu, you can click File -> Save solution-name.sln As... This would bring the Save File As dialog box where you can specify the name of the solution and click Save.
If you don't like the name of a solution, to rename it, in the Solution Explorer, right-click it and click Rename:
As an alternative, in the Solution Explorer, click the name of the project, in the Properties window, click the value of the (Name) field, then edit it or type a new one:
Deleting a Solution is equivalent to deleting a file. To delete a solution, use a file utility such as Windows Explorer, locate the folder that contains the solution, and delete it.
If you are creating your application using a text editor, you must save your file(s) in a folder you will create. When Microsoft Visual Studio 2010 (any edition) is installed, it creates a folder named Visual Studio 2010 in your Documents folder. The Documents folder is called your personal drive or your personal directory. Inside of the Visual Studio 2010 folder, it creates a sub-folder named Projects. By default, this is where it would save your projects, each with its own folder.
To save a project, on the Standard toolbar, you can click the Save All button . Alternatively, on the main menu, you can click File -> Save All. If the project had already been saved but you want to save it under a different name, on the main menu, you can click File -> Save project name As...
There are a various ways you can open an existing project:
A solution in Microsoft Visual Studio can contain one or more projects. That is, after creating the first project, you can add another project to the same solution and you can add as many projects as you want.
To add a new project to a solution (in Microsoft Visual Studio):
This would display the Add New Project dialog box. In the Templates list, select the type of project you want. Accept or change the name of the project, then click OK.
The names of the different projects are listed in the Solution Explorer.
To rename a project, in the Solution Explorer, right-click its name under the solution and click Rename. Type the new name and press Enter.
As mentioned already, a project can contain many files. If you are using a text editor, you can create and save files continuously as you see fit. If you are using Microsoft Visual C# 2010 Express or Microsoft Visual Studio, to add a new file to a project:
This would display the Add New Item dialog box. From there, select the type of file you want. Accept or change its name. Then click Add.
When a project is made of various files, each file is represented by a label in the top section of the Code Editor. Here are examples:
Each file is also represented in the main menu under Windows.
When working on a project, if there is a file in another project and you want to use that file in your project, you can import that file. To do this;
Any of these actions would display the Add Existing Item dialog box with the name of the project on the title bar. Locate the file, select it, and click Open.
If you are using a text editor to write your code, you can use that editor to open a file. For example, in Notepad, you can click File -> Open... If you are trying to open a source file, first change the file type combo box to All Files (*). Then locate the file from its folder and click Open.
In Microsoft Visual Studio or Microsoft Visual C# Express, if a file is a member of the current project, to open it:
To open a file:
This would display the Open File dialog box. From there, locate the file from its folder and click it.
You can change the name of a file after starting a project. To do this, in the Solution Explorer, under the project that holds the file, right-click the file and click Rename. Type the desired name and press Enter.
If you have a file in a project but do not need that file anymore, you can delete it. To remove a file, in the Solution Explorer, under the project, right-click the name of the file and click Delete.
After creating or opening a file, you can add the necessary code to it. Microsoft Visual Basic ships with many skeleton codes you can use and customize. It writes the primary code for you and add all the necessary default behaviors. Once it has done this, you can change or remove any section. To access these code skeletons, in the section of the file where you want to add it, right-click and click Insert Snippet...:
In the menu that comes up, double-click a category:
Then double-click another category. This would display a list of code types:
If you see the type of code you want to use, double-click it.
In some cases, if you have already written some code, you may want to change it or rather add some code to it. The Code Editor provides some skeleton codes you can use. To use this approach, right-click the code you want to modify and click Surround With... In the list that appears, double-click the desired option.
If you add many files to a project, you must specify what file should be processed first. If you create a console application using Microsoft Visual Studio or Microsoft Visual Basic 2010 Express, the first file you create is set as the default.
To specify the starting file of your project, on the main menu, click Project -> ProjectName Properties... In the Startup Object combo box, select the file.
Code is written in a wide area with a white background. This is the area you use the keyboard to insert code with common readable characters. The Code Editor uses some colors to differentiate categories of words or lines of text.
The colors used are highly customizable. To change the colors, on the main menu, you can click Tools -> Options... In the Options dialog box, in the Environment section, click Fonts and Colors. To set the color of a category, in the Display Items section, click the category. In the Item Foreground combo box, select the desired color. If you want the words of the category to have a colored background, click the arrow of the Item Background combo box and select one:
In both cases, the combo boxes display a fixed list of colors. If you want more colors, you can click a Custom button to display the Color dialog box that allows you to "create" a color.
Indentation is another feature that makes your program easy to read. Indentation is a technique of grouping lines of code by category. To delimit the items of your code, you should indent them by two empty spaces or one tab. Indentation should be incremental. That is, when a line of code appears to be a child of the previous line, the new line should be indented.
To control the indentation of your code, on the main menu, click Tools -> Options... In the left list, Text Editor amd expand Basic. You can then use the options in VB Specify and Editor:
After making the changes, click OK to validate or Cancel to ignore.
A comment is text that the compiler does not process when reading your code. As such, a comment can be written any way you want. In the Visual Basic language, the line that contains a comment can start with a single quote. Here is an example:
Module Module1 Sub Main() ' This line will not be considered as part of the code End Sub End Module
Module Module1 Sub Main() ' This line will not be considered as part of the code Rem I can write anything I want on this line End Sub End Module
Comments are very useful and you are strongly suggested to use comments regularly. They can never hurt your code and they do not increase the size of your application. Comments can help you and other people who read your code to figure out what a particular section of code is used for, which can be helpful when you re-visit your code after months or years of not seeing it.
When writing code, you will have to separate different parts with spaces, like the one between Sub and Main. This is referred to as white space. The amount of space you put between two words is not important. The compiler would ignore the white spaces between words. This means that Sub Main() and Sub Main() would the same effect. In the same way
would produce the same effect.
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