1. Clearly Visual Basic: Programming with Visual Basic 2008
Chapter 6
The Secret Code

2. Objectives Include a comment in the Code Editor window
Use the Val function to convert text to a number
Write expressions containing arithmetic operators
Write an assignment statement
Clearly Visual Basic: Programming with Visual Basic 2008

3. The Fun Starts Here Coding the algorithm Figure 6-1 Figure 6-2
Fifth step in the problem-solving process
Figure 6-1
Shows the Addison Smith problem’s interface
Figure 6-2
Shows the problem’s output, input, and algorithm
Clearly Visual Basic: Programming with Visual Basic 2008

4. Clearly Visual Basic: Programming with Visual Basic 2008

5. Clearly Visual Basic: Programming with Visual Basic 2008

6. The Fun Starts Here (continued)
Comment: internal documentation
Message to person reading the code
Makes code more readable
Created by placing an apostrophe (’) before the text that represents the comment
Clearly Visual Basic: Programming with Visual Basic 2008

7. Open the Commission Calculator Project and insert the comment statement
Clearly Visual Basic: Programming with Visual Basic 2008

8. The Val Function Characters entered in a text box Function
Can be numbers, letters, or special characters
Function
A predefined procedure that performs a specific task and then returns a value after completing the task
Val function
Temporarily converts one or more characters to a number and then returns the number
Clearly Visual Basic: Programming with Visual Basic 2008

9. The Val Function (continued)
Val(text)
Syntax of Val function
Argument
Information passed to the function while function is processing
When an invalid character is encountered in the text argument
Val function stops the conversion process at that point
Clearly Visual Basic: Programming with Visual Basic 2008

10. NOTE: The value (VAL) of Text or an empty box is ZERO
Clearly Visual Basic: Programming with Visual Basic 2008

11. Who’s in Charge of This Operation?
Figure 6-5
Lists the most commonly used arithmetic operators available in Visual Basic
Precedence numbers
Indicate order in which computer performs operation in an expression
Parentheses can be used to override order of precedence
Clearly Visual Basic: Programming with Visual Basic 2008

12. Clearly Visual Basic: Programming with Visual Basic 2008

13. Clearly Visual Basic: Programming with Visual Basic 2008

14. Who’s in Charge of This Operation? (continued)
Integer division operator ( \ )
Used to divide two integers (whole numbers) and then return the result as an integer
Modulus operator (Mod)
Returns the remainder of the division
Clearly Visual Basic: Programming with Visual Basic 2008

15. Expression Result 2^3 8 4 * -3 -12 25/4 6.25 25\4 6 25 Mod 4 1
7 + 6 * (5-2) 25
Mini Quiz:
Write an expression to add 100 to the contents of lblTotal
If the user enters $67.45 in txtTax.Text, what does Val(txtTax.Text) return?
If the users enters 23 in txtTotal, what is the Val(txtTotal.Text) Mod 2

16. Insert the code to calculate the commission
lblCommission.Text = Val(txtSales.Text) * Val(txtRate.Text)
Clearly Visual Basic: Programming with Visual Basic 2008

17. Review Questions
Comments in VB start with an: ‘apostrophe
If the user enters $5 in txtPrice and 3 in the txtQuantity, what is: Val(txtPrice) * Val(txtQuantity)? 0 zero None of These
If the user enters 75 in txtNum, which changes it to a negative 75 (-75)? -txtNum.Text = Val(txtNum.Text) txtNum.Text = txtNum.Text txtNum.Text = -Val(txtNum.Text) None of These
If txtNum contains value 82, which equals 4? (Val(txtNum.Text)+6)/ Val(txtNum.Text) Mod 6 Val(txtNum.Text) \ 20
Which expression will NOT calculate correctly? lblTotal.Text =Val(txtSales1.text)+ Val(txtSales2.text) lblTotal.Text – Val(txtSales.Text + txtSales2.Text) lblTotal.Text = Val(txtRed.Text) * 2 lblTotal.Text =Val(txtBlue.Text) * 1.1

18. Open Commission Calculator- Code the Calculate Button
Change the Rate Box, so that it accepts the rate as a percent and not a decimal. For example, you would enter 6 in for the rate instead of .06
Test the solution with 2000 and 10 for the percent- Results: 200
Lock the program!!
Lock the
Form
Clearly Visual Basic: Programming with Visual Basic 2008

19. Open Tip Calculator- Code the Calculate Button
Clearly Visual Basic: Programming with Visual Basic 2008

20. Vans and More Depot Project Page 112- #5
Create an application for Vans and More Depot, which rents vans for company outings. Each van can transport 10 people. When you enter the number of people in the applications, the program will tell you how many vans you need and how many people need alternate transportation. For example if you enter 48 people, the program will tell you that you need 4 vans and alternate transportation for 8 people
Clearly Visual Basic: Programming with Visual Basic 2008

21. Modified Vans and More Depot Project Page 113- #7
Modify Vans and More Depot so that each van can transport 10 people, each car can transport 5 people, and the rest will have to find other transportation. When you enter the number of people in the applications, the program will tell you how many vans you need, how many cars you need, and how many people need alternate transportation. For example if you enter 48 people, the program will tell you that you need 4 vans, 1 car and 3 people need to find alternative transportations
Clearly Visual Basic: Programming with Visual Basic 2008

22. Page 113 #8 Sun Project
Program will ask for Name, Hours, and Rate. Then it will figure out the net pay after subtracting 20% for Federal Withholding tax, 8% for Social Security tax and 2% for State Income Tax
Clearly Visual Basic: Programming with Visual Basic 2008

23. Page 114- #9 RM Sales (Sales Solution)
Program RM Sales that asks for the amount of sales for each region. The program will compute the sales percentage of each region
Clearly Visual Basic: Programming with Visual Basic 2008

24. Summary Fifth step in the problem-solving process
Code the problem’s algorithm
When you want a procedure to make a calculation
Tell it how to make the calculation and where to store the result
Use comments to internally document a project’s code
Val function
Temporarily converts one or more characters to a number and then returns number
Clearly Visual Basic: Programming with Visual Basic 2008

25. Summary (continued) Arithmetic operators having same precedence number
Evaluated from left to right in an expression
Parentheses
Can be used to override order of precedence for arithmetic operators
Assignment statement
Used to assign a value to something while an application is running
Clearly Visual Basic: Programming with Visual Basic 2008