Objectives

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2. Objectives • Include the repetition structure in pseudocode and in a flowchart • Write a For…Next statement • Calculate a periodic payment using the Pmt function • Write a Do…Loop statement • Initialize and update counters and accumulators • Display a dialog box using the InputBox function Microsoft Visual Basic .NET: Reloaded

3. The Repetition Structure • Repetition Structure (also known as a loop) • Repeatedly processes a set of instructions until a condition is met • Pretest loop: • Evaluation occurs before instructions within loop • PostTest loop: • Evaluation occurs after the instructions within loop are processed • Instructions will always be processed at least once Microsoft Visual Basic .NET: Reloaded

4. The For…Next Statement • Use to code a loop to process instructions a precise number of times • For…Next is a pretest loop • StartValue (starting value of loop counter) • EndValue (ending value of loop counter) • Stepvalue (amount of change of loop counter) • Default stepvalue is a positive 1 • Can be negative • Designate with Step keyword • Example Step -2 • Subtracts 2 from the loop counter Microsoft Visual Basic .NET: Reloaded

5. HOW TO… Microsoft Visual Basic .NET: Reloaded

6. The For…Next Statement (continued) Microsoft Visual Basic .NET: Reloaded

7. The For…Next Statement (continued) Microsoft Visual Basic .NET: Reloaded

8. The Pmt Function • Use to calculate a periodic payment on a loan or investment • Contains 5 arguments • Rate, Nper, PV are required • FV, Due are optional • Negation operator reverses the sign of a number • -Pmt(.05,3,9000) Microsoft Visual Basic .NET: Reloaded

9. HOW TO… Microsoft Visual Basic .NET: Reloaded

10. The Payment Calculator Application Microsoft Visual Basic .NET: Reloaded

11. The Payment Calculator Application (continued) Microsoft Visual Basic .NET: Reloaded

12. The Do…Loop Statement • Can be used to code both pretest and posttest loops • Do While or Do Until is a pretest loop • Pretest loops should have a “priming read” • Data input entry placed above loop • Loop While or Loop Until is a posttest loop • [While|Until] portion can only contain one of the keywords (While or Until) • While processes instructions as long as the condition evaluates true • Until processes instructions until the condition becomes true Microsoft Visual Basic .NET: Reloaded

13. HOW TO… Microsoft Visual Basic .NET: Reloaded

14. The Do…Loop Statement (continued) Microsoft Visual Basic .NET: Reloaded

15. The Do…Loop Statement (continued) Microsoft Visual Basic .NET: Reloaded

16. The Do…Loop Statement (continued) Microsoft Visual Basic .NET: Reloaded

17. The Do…Loop Statement (continued) Microsoft Visual Basic .NET: Reloaded

18. The Do…Loop Statement (continued) Microsoft Visual Basic .NET: Reloaded

19. Using Counters and Accumulators • Counter – numeric variable used for counting something number of employees paid in a week • Accumulator – numeric variable used for calculating running totals total dollar amount of weeks payroll • Initializing – assigning a beginning value to a variable • Updating (incrementing) – adding a number to the value stored in the counter or accumulator Microsoft Visual Basic .NET: Reloaded

20. The Sales Express Application • Application for sales manager to display average amount the company sold during the prior year. • Sales manager will enter each salesperson’s sales • Application will use a counter to keep track of number of sales amounts and an accumulator to total those amounts Microsoft Visual Basic .NET: Reloaded

21. The Sales Express Application (continued) Microsoft Visual Basic .NET: Reloaded

22. The InputBox Function • Displays a dialog box that prompts the user in input information • Contains a prompt, one or more buttons, and an input area for data entry • Prompt - message you want displayed • Title displays caption of input box • defaultResponse - initial text displayed in the input area • Ok button returns value in input area, Cancel and Close buttons return empty string Microsoft Visual Basic .NET: Reloaded

23. The InputBox Function (continued) Microsoft Visual Basic .NET: Reloaded

24. The InputBox Function (continued) Microsoft Visual Basic .NET: Reloaded

25. Code for the Sales Express Application Microsoft Visual Basic .NET: Reloaded

26. Programming Example – Grade Calculator • Application allows the user to enter the points a student earns on 4 projects and 2 tests • Totals the points earned and calculates grade • Total Points Earned Grade 360-400 A 320-359 B 280-319 C 240-279 D below 240 F • Displays total points and grade earned Microsoft Visual Basic .NET: Reloaded

27. TOE Chart Microsoft Visual Basic .NET: Reloaded

28. User Interface Microsoft Visual Basic .NET: Reloaded

29. Objects, Properties, and Settings Microsoft Visual Basic .NET: Reloaded

30. Objects, Properties, and Settings (continued) Microsoft Visual Basic .NET: Reloaded

31. Tab Order Microsoft Visual Basic .NET: Reloaded

32. PseudoCode btnExit Click event procedure Close application btnAssignGrade Click event procedure 1. repeat while the number of projects counter is less than 5 if the points earned is numeric add the project points to the total points accumulator add 1 to the number of projects counter else display an appropriate message in a message box end if end repeat (continued on next slide) Microsoft Visual Basic .NET: Reloaded

33. PseudoCode (continued) 2. repeat while the number of tests counter is less than 3 get the points earned on the test if the points earned is numeric add the test points to the total points accumulator add 1 to the number of tests counter else display an appropriate message in a message box end if end repeat (continued on next page) Microsoft Visual Basic .NET: Reloaded

34. PseudoCode (continued) 3. Assign the grade based on the total points earned value: >= 360 assign A as the grade >= 320 assign B as the grade >= 280 assign C as the grade >= 240 assign D as the grade <240 assign F as the grade 4. Display the total points earned in lblTotalPoints 5. Display the grade in lblGrade Microsoft Visual Basic .NET: Reloaded

35. Code Microsoft Visual Basic .NET: Reloaded

36. Code (continued) Microsoft Visual Basic .NET: Reloaded

37. Summary • Three programming structures are sequence, selection, and repetition • Repetition (loop) allows program to repeatedly process one or more program instructions • Pretest loops test before program instructions • Posttest loops test after program instructions and will always be processed at least once • Pmt function calculates payment on a loan Microsoft Visual Basic .NET: Reloaded

38. Summary (continued) • The condition in a loop evaluates to a Boolean variable • While processes loop instructions while the condition is true • Until processes loop instructions until the condition becomes true • Use a counter or accumulator to calculate subtotals, totals and averages • Counters and accumulators must be initialized and updated Microsoft Visual Basic .NET: Reloaded

39. Summary (continued) • InputBox Function displays a dialog box that displays a message, an OK button, a Cancel button, and an input area. • Test for possible division by zero to prevent an error ending the program prematurely Microsoft Visual Basic .NET: Reloaded