Sams Teach Yourself Visual Basic 6 in 24 Hours

By Greg Perry

• Table of Contents
  • Copyright
  • About the Author
  • Acknowledgments
  • Introduction
  • Who Should Read This Book
  • What This Book Will Do for You
  • Can This Book Really Teach Visual Basic in 24 Hours?
  • What You Need
  • Files on the Visual Basic Distribution CD-ROM
  • Conventions Used in This Book
  • Enough! Time Is Ticking!
  • Part I: Introducing Visual Basic
  • Hour 1. Visual Basic at Work
  • Hour 2.Analyzing Visual Basic Programs
  • Hour 3.Controls and Properties
  • Hour 4.Examining Labels, Buttons, and Text Boxes
  • Part II: Coding the Details
  • Hour 5.Putting Code into Visual Basic
  • Hour 6.Message and Input Boxes
  • Hour 7.Making Decisions
  • Hour 8.Visual Basic Looping
  • Part III:Putting Code to Work
  • Hour 9.Combining Code and Controls
  • Hour 10.List Boxes and Data Lists
  • Hour 11.Additional Controls
  • Hour 12.Dialog Box Basics
  • Part IV:Programming with Data
  • Hour 13.Modular Programming
  • Hour 14.Built-In Functions Save Time
  • Hour 15.Visual Basic Database Basics
  • Hour 16.Printing with Visual Basic
  • Part V:Sprucing Up Programs
  • Hour 17.Menus and Visual Basic
  • Hour 18.The Graphic Image Controls
  • Hour 19.Toolbars and More Graphics
  • Hour 20.Writing Correct Applications
    • Kinds of Errors
    • The Debugger
    • Setting Breakpoints
    • Stepping Through Code
    • The Call Stack Shows Where You've Been
    • The Immediate Window
    • Summary
    • Q&A
    • Workshop
  • Part VI:Advancing Visual Basic Applications
  • Hour 21.Visual Basic and ActiveX
  • Hour 22.Object Basics
  • Hour 23.Distributing Your Applications
  • Hour 24.Online Visual Basic
  • Part VII:Appendixes
  • Appendix A.Operator Precedence
  • Appendix B.Answers
  • Appendix C.Using the CD-ROM

Stepping Through Code

One of the most powerful debugging features is the single-step feature mentioned at the end of the previous section. At the breakpoint you set, only one additional statement (other than remarks, which don't execute) resides in the procedure, and that statement is a procedure call to another procedure named DisplayCaption().

The Debug menu's Step Into option (also available on the Debug toolbar) executes each statement in the program, including all the statements in procedures called. Therefore, if you single-step through the code from the breakpoint, the DisplayCaption() procedure executes (you can follow the yellow highlight to see the execution). After you step through the DisplayCaption() procedure, control returns to the opt486_Click() procedure that called DisplayCaption(), and then you can single-step back to the procedure that called opt486_Click().

If you want the effects of the single-step without going through every line of code, you can select the Debug menu's Step Over option. The Step Over option won't single-step through subsequent procedures called, but will run each call individually without single-stepping through the lines in the procedures. In other words, you can single-step through the next subroutine procedure's Call statement (or function call), but when you then single-step, control doesn't go into that procedure; the procedure executes as normal and then you get the single-step control back again. The Step Over option is useful when you've debugged procedures called by the current procedure and you don't want to waste additional time single-stepping through a procedure you've already debugged.

The Debug menu's Step Out option executes the rest of the current procedure without executing the procedure in single-step mode. When the current procedure finishes and control returns to the procedure that called the current procedure, execution begins once again in single-step mode.

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