Book Image

Visual Basic Quickstart Guide

By : Aspen Olmsted
Book Image

Visual Basic Quickstart Guide

By: Aspen Olmsted

Overview of this book

Whether you’re an absolute beginner or an experienced developer looking to learn the Visual Basic language, this book takes a hands-on approach to guide you through the process. From the very first chapters, you'll delve into writing programs, exploring core concepts such as data types, decision branching, and iteration. Additionally, you’ll get to grips with working with data structures, file I/O, and essential object-oriented principles like inheritance and polymorphism. This book goes beyond the basics to equip you with the skills to read and write code across the entire VB family, spanning VB Script, VBA, VB Classic, and VB.NET, enabling you to handle legacy code maintenance with ease. With clear explanations, practical examples, and hands-on exercises, this book empowers you to tackle real-world software development tasks, whether you're enhancing existing projects or embarking on new ones. It addresses common challenges like distinguishing between the variations of the VB programming language to help you choose the right one for your projects. Don't let VB's extensive legacy daunt you; embrace it with this comprehensive guide that equips you with practical, up-to-date coding skills to overcome the challenges presented by Visual Basic's rich history of over two decades.
Table of Contents (27 chapters)
Free Chapter
1
Part 1:Visual Basic Programming and Scripting
9
Part 2:Visual Basic Files and Data Structures
14
Part 3:Object-Oriented Visual Basic
20
Part 4:Server-Side Development

Building the project in VB6

We will now build Visual Basic 6 code for a simple calculator program. The program has a form that loads when the application starts. The form contains a loop that prompts the user to input two numbers and an operator and then operates on the two numbers. The loop prompts the user until they enter X to quit. Finally, the program displays the result of the operation in a message box. For example, if the user tries to divide by zero, a message box says, "Cannot divide by zero!". The program uses the Cint function to convert the inputted numbers into integers and handles errors using message boxes:

Private Sub Form_Load()
  Dim n1, n2, res, operator, sentinel As String
  sentinel = False
  Do
    n1 = InputBox("Enter the first number or X to quit:")
    If n1 = "X" Then
        sentinel = True
    ...