Introduction To Visual Basic 6

Announcements  Thursday, Oct 9th, 7:30PM, C106 Lloyd Douglas (NSF) Diversity in Science-Who needs it? 5 extra credits.  About the extra credit Please submit printed copy. Don’t hand in through blackboard system or send .

Programming language  Programming is writing instructions for a computer.  Level of programming languages Machine language – 0s and 1s Intermediate languatge – assambly language. High level language – BASIC, C++ …

Interpreting or compiling  How do computers handle the high level language? Read and Interprete the code line by line with an program called interpreter, e.g. BASIC. Translate the language to machine code (executable files) with a program called compiler and run the program, e.g. C++. Visual basic has both Interpreter and Compiler.

History of BASIC  Basic --- Beginners' All-purpose Symbolic Instruction Code (May, 1964)  MS-BASIC 2.0 (July, 1975)  Visual Basic 1.0 (May,1991)  Visual Basic 6.0 (July 1998)

Why do we learn Visual Basic  It shares the same principles with other programming languages.  It is good when developing small and handy utility programs.  It is supported by Microsoft.  It is powerful when integrated with Excel and Word.

Six Steps in Programming  Problem Identification  Solution Design  Coding  Compiling with compiler or running with interpreter  Debugging  Testing

Step 1 and 2: Problem Identification and Design  Identify what needs to be solved Make diagrams, and equations, etc  Design: Analyze the problem and develop an ALGORITHM and FLOWCHART

Step 3: Source Code  Creating “Source Code” Source Code is the instructions for the computer written in Visual Basic programming language In VB, source code is linked to an object on the form Designing user interface is also part of the coding.

Step 4a:Compiling  Compiling converts Visual Basic source code to “executable” machine language - instructions the processor can understand (1s and 0s)  Creates.exe file  Advantage: Fast and small  Disadvantage: Debugging is inconvenient.

Step 4b: Interpreting  Interpreting reads and runs one line of code each time.  You can find “Grammar errors” in this stage.  Advantage: Good for debugging Interpreter is easy to program.  Disadvantage: Slow

Interpreting and Compiling in VB

Step 5: Debugging  Debugging is removing the “functional errors” from your program  Running tells you where there are errors  Go back to source code and fix errors  Save and re-run  Repeat until errors are gone

Step 6: Testing and Running  Try to run the program by pressing the start button  If it starts running, enter the answers and/or click the buttons to test it  Test your program with boundary and special cases.

Visual Basic Programming  VB is a programming language that allows you to program in a Windows environment  You create a “Form” with several “Objects”  You set the properties of objects.  You write event handler to response to user’s input.

VB programming Project Form 1Form 2Form 3 Text boxButton Picture box Objects Text box Button Objects

Definitions  Form contains the Main Program  Controls are user interface elements (text boxes, commands) in the Form  Forms and Controls are referred to as OBJECTS  Objects have PROPERTIES (features you can change)

Forms in Visual Basic  You create a form that is your graphical user interface  Has places to input values  Has buttons to click  Has other user interface elements, e.g. Menu, scroll bar…

Objects in VB  Everything in VB is objects, forms, buttons,…  Three elements of objects. Properties Methods Event handlers. Properties (size, Caption…) Methods (Print…) Event Handler (Command1_Click()) VB object

Object: Dog  Properties Height, weight, color, emotion (friendly, hostile)…  Methods Barking, biting, wagging, singing…  Event handlers Owner coming in: call wagging, call singing, emotion=friendly; Intruder coming in: call barking, call biting, emotion=hostile.

Important Controls  Text Boxes – area where you enter text  Command Buttons – you click on them to do something  Picture Boxes – Output your results.

Text Boxes  Properties: Name (of object) Text (the words) Alignment (left, right, middle) Appearance BackColor (background) BorderStyle Font FontColor

Command Button  Properties: Name BackColor Style (This controls the backcolor) Caption

Picture Boxes  Properties Name Picture  Methods Print

Definitions Objects Forms Command Button properties Methods properties Methods Textbox properties Methods Picture Box properties Methods Label properties Methods Handlers properties Methods

“ Design time ” and “ Run time ”  When you design you can use the property window to set the property of certain object.  When you run the program, you can only use code to change the property of that object.

Just a Bunch of Objects  Q: Now that you have a bunch of objects, how do you make them react to your command? A: Sub Procedures  Sub Procedures are the instructions  Sub Procedures go with Events (Like clicking a button)

How the test program works

Message Dispatching Block User Text box Properties Methods Event Handler Button Properties Methods Event Handler Picture Box Properties Methods Event Handler You have got letters. You have got clicked.

Making It Do Something  Want program to change on an “Event” Events:  MouseDown  MouseUp  Click  Need to create Sub Procedures  Sub Procedure handles Event and changes Properties of an Object

Sub Procedure  Two Objects: Text1 and Command1 Sub Procedure: Private Sub Command1_Click() Text1.FontSize = 18 End Sub  When Command1 is clicked, the FontSize property of Text1 is changed to 18

Sub Procedure Private Sub CommButt_Click() Text1.FontSize = 18 Text1.BackColor = vbBlue Command1.Caption = "Get Some Now" End Sub

Homework  Read Chapters 1 & 2 in book