Visual Basic Intro

Introduction To Visual Basic 6

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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 1 Form 2 Form 3

Text box Button

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

ObjectsForms Command

Buttonproperties

propertiesproperties

propertiesproperties

propertiesproperties

propertiesproperties

propertiesMethods

propertiesproperties

MethodsTextbox

propertiesproperties

propertiesproperties

properties

propertiesproperties

propertiesMethods

Picture Boxproperties

propertiesproperties

propertiesproperties

properties

propertiesproperties

propertiesMethods

Label

propertiesproperties

propertiesproperties

propertiesproperties

propertiesproperties

propertiesMethods

Handlers

propertiesMethods

“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

How the test program works

MessageDispatching

Block User

Text box

Properties

Methods

Event Handler

Button

Properties

Methods

Event Handler

PictureBox

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 Command1Sub Procedure:Private Sub Command1_Click()

Text1.FontSize = 18

End Sub

When Command1 is clicked, the FontSize property of Text1 is changed to 18

Sub ProcedurePrivate Sub CommButt_Click()

Text1.FontSize = 18

Text1.BackColor = vbBlue

Command1.Caption = "Get Some Now"

End Sub

Homework Read Chapters 1 & 2 in book