1. Clearly Visual Basic: Programming with Visual Basic 2010 2nd Edition
Chapter 14
Let Me Count the Ways (Counter-Controlled Loops)

2. Objectives After studying Chapter 14, you should be able to:
Code a counter-controlled pretest loop using the For…Next statement
Play an audio file while an application is running
Calculate a periodic payment using the Financial.Pmt method
Concatenate strings
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

3. When Will It Stop? Counter-controlled loop
Loop whose instructions you want processed a precise number of times
Can be either a pretest loop or a posttest loop
Coding a posttest counter-controlled loop
Use the Do...Loop statement
Coding a Pretest counter-controlled loop
Use either the Do…Loop statement or the For…Next statement
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

4. When Will It Stop? (cont’d.)
For…Next syntax
Shown in Figure 14-1 on next slide
CounterVariableName
Name of numeric variable
Can be declared in a Dim statement
To have procedure scope
Variable declared in the For clause:
Has block scope and can be used only within the loop
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

5. When Will It Stop? (cont’d.)
startValue, endValue, stepValue
Numeric items in the For clause
Control the number of times loop is processed
Can be positive or negative, integer, or non-integer
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

6. Figure 14-1 Syntax, example, and processing tasks for the For…Next statement (continues)
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

7. Figure 14-1 Syntax, example, and processing tasks for the For…Next statement (cont’d.)
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

8. Figure 14-2 Processing steps for the example in Figure 14-1
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

9. Spaceship-Version 1 Application
Figure 14-3
Shows the interface for the Spaceship-Version 1 application
Before coding the Spaceship-Version 1 application:
View the Ch14-Spaceship video
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

10. Spaceship-Version 1 Application (cont’d.)
Figure 14-3 Interface for the Spaceship-Version 1 application
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

11. Spaceship-Version 2 Application
Display the numbers 3, 2, and 1 in the lblCountToBlastOff control
Figure 14-5 For…Next statement entered in the Go button’s Click event procedure in the Spaceship-Version 2 application
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

12. Hey, Turn That Noise Down!
To have an application play an audio file while it is running:
Use the syntax My.Computer.Audio.Play(fileName)
Visual Basic’s My feature
Exposes a set of commonly used objects to the programmer
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

13. The Monthly Payment Calculator Application
Figure 14-6
Shows the interface for the Monthly Payment Calculator application
Figure 14-7
Shows the application’s output, processing, and input items, along with its algorithm
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

14. The Monthly Payment Calculator Application (cont’d.)
Figure 14-6 Interface for the Monthly Payment Calculator application
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

15. Figure 14-7 Output, processing, input, and algorithm for the Monthly Payment Calculator application
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

16. The Financial.Pmt Method
Calculates the periodic payment on a loan
Figure 14-8
Shows the method’s basic syntax
Lists the meaning of each of the three arguments included in the syntax
Gives examples
Can also be used to calculate periodic payment on an investment
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

17. Figure 14-8 Basic syntax and examples of the Financial.Pmt method
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

18. But They Said There Were No Strings Attached
Concatenation operator
Represented by ampersand (&)
Used to concatenate (connect or link) strings
Must use a space before and after the ampersand
Figure 14-9
Shows syntax and examples of using the concatenation operator
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

19. Figure 14-9 Syntax and examples of concatenating strings
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

20. Summary The For…Next statement Variable declared in a For clause
Provides a convenient way to code a counter-controlled loop
Variable declared in a For clause
Has block scope
Can be used only by the For…Next loop
The For…Next statement’s counter variable must be numeric
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition

21. Summary (cont’d.) The syntax My.Computer.Audio.Play(fileName)
Can be used to play an audio file while an application is running
Financial.Pmt method
Used to calculate a periodic payment on a loan or investment
Concatenation operator (&)
Used to connect strings
Clearly Visual Basic: Programming with Visual Basic 2010, 2nd Edition