Introduction Overview of VB

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IntroductionOverview of VB
Chapter
ONE
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Characteristics of Business Applications

• Require some customization but do not rely
  heavily on sophisticated mathematical analyses.
• Business environment is frequently changing and
  applications must reflect the realities of the
  environment.

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What is Visual Basic?

• Visual Basic (VB) is a programming environment
  that provides two things to the programmer
• A set of programming tools which enable the
  programmer to assemble and rearrange the
  components (objects) of the program under
  construction.
• A programming language which enables the
  programmer to compose the instructions that tell
  the computer how to perform the tasks required by
  the program under construction.

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What is Visual Basic?

• Programming Environment
• Controls (objects)
• Language
• Visual graphical user interface (GUI)
• Event-driven
• Rapid Application Development and prototyping
  tool (RAD)

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Event-Driven Programming

• Visual Basic is used for creating event-driven
  application programs.
• Events are generated by the user, and the
  application program responds to them.
• Typically, a user enters data on a screen and
  presses command buttons to initiate program
  action.

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Conventional Programming Text-based Sequential
flow of control Control flow guided by the
application Program development is
non-interactive
Event-Driven Programming GUI-based No
predetermined flow of control Functions
triggered by user-generated
events Program development is interactive

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VB Uses the Windows Environment

• Mouse and mouse pointer
• Mouse operations -- pointing, clicking, double
  clicking, dragging
• Menus and commands
• Standard controls (Dialog boxes, Check boxes,
  text boxes, command buttons, etc.)
• Similar look and feel
• Multiple approaches to any operation

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Example Order Entry Screen
Used by a computer equipment retail outlet to
record data regarding customer orders.
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Characteristics of a good application

• Does what is needed
• Does it correctly
• Is easy to use
• Code is organized and maintainable
• Program is flexible

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A formal procedure for creating applications

• Identify user requirements
• Design the application GUI - User
  Interface/Properties Functionality/Logic
• Construct the application Build
  GUI (forms/controls/properties) Write the
  code Test

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IDE (Integrated Development Environment) VB 6
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Toolbar and toolbox
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The Properties window
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Completed Order Entry form
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(No Transcript)
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The Code window
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Structure of VB projects
.VBP
Project
0 or 1
1
.FRM
0
Custom Controls .VBX/.OCX
Resource file
0
Forms
.BAS
Class modules
1
0
Code modules
General declarations section
1
0
Controls
General sub procedures
General declarations section
0
1
General sub procedures
Event procedures
Properties
Methods
The structure of class modules has been omitted
for clarity.
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Structure of VB projects (simplified)
.VBP
Project
1
Forms
.FRM
0
Controls
1
0
Event procedures
Properties
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Project

• Visual Basic runs under the Windows operating
  system.
• The programmer uses VB to create the application.
  The application under construction in VB is
  called a project.

Break time
Programmer
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Project

• The programmer periodically saves the project to
  disk.

Break time
Programmer
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Project

• The programmer periodically saves the project to
  disk.
• The completed project is made into an executable
  file, which VB stores on disk. This file
  contains the finished application program.

Break time
Programmer
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Project

• The programmer periodically saves the project to
  disk.
• The completed project is made into an executable
  file, which VB stores on disk. This file
  contains the finished application program.
• The application is delivered to the user.

Break time
Programmer
Finished Application
User
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• The application runs under the Windows operating
  system independently of VB.
• The executable file cannot be modified if
  changes to the application are required, the
  programmer must use VB to open the project files,
  modify the project, and then make a new
  executable file.

Programmer
Finished Application
User