Wyo VB - Ch. 2 Notes

Objective #1: Recognize the components of the Visual Basic programming environment.

• The form window is your basic environment on which you place objects that will be seen by the user.
• The Solution Explorer window shows the filenames of all of the form (.vb) files that are contained in your current project.
• The Properties window allows you to set most any property of the object which is currently selected (i.e. highlighted) in the form window.
• The Toolbox usually appears along the left edge of the screen. It contains the tools that you use to place controls on a form. You can double click a tool to cause a control to appear on the current form. You can also pass your mouse over each tool to see the name of the tool appear in a pop-up window.
• The main Visual Basic window holds the menu bar (at the very top) and the Toolbar (just under the menu bar).
• The Help menu is a very useful and often overlooked repository of information. Use the online Help to learn about Visual Basic!

Objective #2: Identify objects, properties, and methods and explain how they are different.

• Objects are generally any thing that you introduce within a VB project. Examples of objects include forms and controls. Forms are the building blocks of your programs. A form is a window on which you place other objects. Sometimes a form can take the form of a dialog box which you are accustomed to seeing in almost every Windows program. Controls are the things that you place on top of forms. Controls include text boxes, command buttons, and labels.
  
  In the statement,
  
  lblHello.Text = "Hello World"
  
  lblHello is the name of an object. Specifically, it is a label.
  
  
• Properties are associated with objects. Any single object has numerous properties that affect the way it is displayed and the way that it interacts with the user and other objects. Referring to properties is tricky. You must first include the name of the object, followed by a period, and then the name of the property.
  
  In the statement
  
  lblHello.Text = "Hello World"
  
  Text is the name of a property. It is a property of the label named lblHello. The value of the property is being set to the string value "Hello World" in this statement.
  
  
• Methods are actions that a programmer can use with objects. For example, printing an object such as a form is a method of that form.
  
  In the statement
  
  ?????
  
  ??? is the name of a method. It is a method that works with ???? objects. This statement causes ????
  

Objective #3: Write, run, save, print, and modify a Visual Basic project.

• Type the code, which you have been required to memorize for this class, into the code window of a blank form that must be named frmHello.vb
• Click the Run tool on the toolbar in order to execute the project.
• Click the Stop tool on the toolbar to stop the execution.
• Choose the Print menu option "Print Code".
• Change the Hello World phrase to something else and execute the program again to see the change.

Objective #4: Describe the various files that make up a Visual Basic project.

• Visual Basic programs can be called projects. VB is a more complicated programming environment than older versions of Basic. The project consists of the following files:
  
  
  • A .vbp file which is the project file. You rarely would have to edit this file but you must be aware of its existence and placement.
  • One or more .frm files which each refer to the form windows that the user will see during program execution. This file contains references to the objects and their properties that are located on the particular form. A form file is really called a form module in VB.
  • More advanced programs will also include .bas files. These files are called standard code modules and contain external procedures that can be used by any form within the project.
  • Even more advanced programs may include .ocx files which contain custom controls. Usually you will be able to write a program that only requires the standard control set which is included with your version of VB. But you can purchase sophisticated controls from third-party developers and use them within your project.
  • A .vbw file is saved for each VB project that you create. Visual Basic holds information necessary to execute the program here.
    
    
• VERY IMPORTANT:    You must always create a new folder to store all of a projects associated files before you begin the project. Be sure to create the project within this folder so that you will be able to find all of the necessary, associated files in the future. After creating a VB project, you must be very careful if you have to move a form module or other file because this may render your program unexecutable. Also, do not rename files after creating them unless you know what you are doing.

Objective #5: Define design time, run time, and break time.

• Design time refers to the period of development in which you carefully plan and design the user interface. You also write out the pseudocode and the actual code during design time.
• When you are testing and debugging your program, you are in the midst of run time.
• If an error or bug stops your program, you experience what is called break time.

Objective #6: Identify compile errors, run-time errors, and logic errors.

• A compile error is often caused by a mispelled keyword or a missing or misplaced symbol. Incorrect syntax often causes a compile error. Syntax means the grammar of a programming language. In Visual Basic, compile errors often cause a line of code to appear in red.
• A run time error often causes a program to stop or crash. These types of errors can be hard to predict. A typical run time error is caused by dividing by zero in a program. Since dividing by zero is not a spelling error, it does not show up highlighted in red as a compile error. Rather, when the program runs, it causes the program to crash.
• A logic error is often harder to find than compile or run time errors. A logic error often results in an incorrect computation and incorrect output. This kind of error does not cause a program to crash in most cases.

Objective #7: List and describe the 3 steps for writing a Visual Basic project.

• You must always plan a program before you actually write it to be a successful programmer. Many students and professionals overlook this crucial necessity.
  
  
  • Design the user interface:    You should storyboard the program by actually drawing pictures of the screen that the user will interact with during the program's execution. Show the forms and controls carefully and accurately. Do NOT assume that you will be able to "figure it out" when you sit down to type the code into the computer. It is highly recommended to name the forms and controls that you plan to use beforehand rather than to write them into the code as you type it as well.
  • Plan the properties:    Since it is possible to highly customize the look and feel of a VB program (unlike older procedural programs), it is very important to write down your ideas and plans before typing the code into the computer. Your program will not have a commercial and professional appearance, otherwise.
  • Plan the code:    Write out pseudocode that explains the procedural tasks that must be accomplished within your program before typing or even writing out actual Basic code. Pseudocode is English phrases that roughly explains how you plan to do things within your program. Do not use Basic keywords or perfect syntax during this planning phase.

Objective #8: Know how to place textboxes, labels, and command buttons on a Visual Basic form.

• One simply needs to double-click on a Toolbox icon in order to place that object on the form. You may have to drag objects around the form in order to be able to see newly created ones.
  
• You can also single-click the Toolbox icon and then click and drag on the form itself to place and size an object.

Objective #9: Be familiar with the naming convention used for forms, textboxes, labels, and command buttons.

•  You must use the InterCap method with the conventional prefixes when naming controls and objects. Always begin a control's name with the correct prefix (3 lowercase letters) that identify the type of control that you are naming.
• You should always rename the form in your project to frmMain. While VB automatically assigns the default name of Form1 to the first form in your project, you should immediately rename it in the Property window. Any other forms that you add to your project should also have the frm prefix in their name.
• You should always rename textboxes, command buttons and most labels as soon as you place them on a form. Use logical and relevant names that describe the purpose of such objects but you must include the prefix lbl with labels, txt with textboxes, and cmd for command buttons.