All Categories : C/C++

---

---

- Project 7 -
Break It Up with Functions

In this lesson, you learned about functions. You saw the following:

• Writing your own functions.
  
  
• How to determine the difference between local and global variables.
  
  
• How to pass data to a function.
  
  
• How to return data from a function.
  
  
• How to use the same function name with different parameters.
  
  
• How to default values.
  
  

Project 7 Listing. A multifunction program that passes data between functions.

  1:// Filename: PROJECT7.CPP

  2:// A multifunction program that computes payroll amounts

  3:#include <iostream.h>

  4:

  5:

  6:void GetPayrollInput(char name[], float &rate, int &hours);

  7:float CalcWages(float rate, int hours);

  8:float CalcTaxes(float pay, float taxRate = 0.34);

  9:void PrintResults(const char name[],float pay, float taxes);

 10://

 11:// Overloaded input functions to get individual values

 12://

 13:void GetInput(const char prompt[],char string[]);

 14:void GetInput(const char prompt[],float& number);

 15:void GetInput(const char prompt[],int& number);

 16:void main()

 17:{

 18:  int hours;

 19:  float rate, pay, taxes;

 20:  char employee[30];

 21:  GetPayrollInput(employee, rate, hours);// Get the input data

 22:  pay = CalcWages(rate, hours);// Calculate payroll results

 23:  taxes = CalcTaxes(pay);      // Calculate payroll taxes

 24:  PrintResults(employee, pay, taxes);    // Print the results

 25:  return;   // Return to QuickWin

 26:}

 27://************************************************************

 28:void GetPayrollInput(char name[], float &rate, int &hours)

 29:{

 30:  // Code to get employee data

 31:  GetInput("Employee name? ",name);

 32:  GetInput("How many hours did this employee work? ",hours);

 33:  GetInput("What is the pay rate per hour? ",rate);

 34:  return;   // Return to main()

 35:}

 36://************************************************************

 37:void GetInput(const char prompt[], char string[])

 38:  {

 39:    cout << prompt;

 40:    cin.getline(string,30);

 41:    return;

 42:  }

 43://************************************************************

 44:void GetInput(const char prompt[], float& number)

 45:  {

 46:    cout << prompt;

 47:    cin >> number;

 48:    return;

 49:  }

 50://************************************************************

 51:void GetInput(const char prompt[], int& number)

 52:  {

 53:    cout << prompt;

 54:    cin >> number;

 55:    return;

 56:  }

 57://************************************************************

 58:float CalcWages(float rate, int hours)

 59:{ // Code to calculate payroll amounts

 60:  return (rate * (float)hours);   // Return to main()

 61:}

 62://************************************************************

 63:float CalcTaxes(float pay, float taxRate)

 64:{ // Code to compute taxes

 65:  return (pay * taxRate);   // Return to main()

 66:}

 67://************************************************************

 68:void PrintResults(const char name[], float pay, float taxes)

 69:{   // Code to print the results

 70:  cout.precision(2);

 71:  cout.setf(ios::showpoint);

 72:  cout.setf(ios::fixed);

 73:  cout << endl << name << " earned a total of $"

 74:       << pay << endl;

 75:  cout << "Before $" << taxes << " in taxes." << endl;

 76:  return;   // Return to main()

 77:}

Output

Employee name? Keith Gutteridge

How many hours did this employee work? 40

What is the pay rate per hour? 25.50

Keith Gutteridge earned a total of $1020.00

Before $346.80 in taxes.

Description

1: A C++ comment that includes the program's filename.

2: A C++ comment that contains the program's description.

3: The cout and cin commands need information in the IOSTREAM.H header file.

4: Blank lines improve your program's readability.

5: Blank lines improve your program's readability.

6: Prototype of payroll input function.

7: Prototype of wages calculation function.

8: Prototype of taxes calculation function with default parameter for tax rate.

9: Prototype of printing function.

10: Comments improve readability.

11: Comments improve readability.

12: Comments improve readability.

13: Prototype of overloaded input function, string version (employee name).

14: Prototype of overloaded input function, float version (hourly rate).

15: Prototype of overloaded input function, int version (hours).

16: main() begins.

17: All functions begin with an opening brace.

18: An integer variable that will hold the number of hours worked.

19: float variables to hold various payroll values.

20: A char array to hold the employee name.

21: Passes rate and hours by reference so that GetPayrollInput() can change them and keep those changed values in main().

22: CalcWages() uses the rate and hours figures to calculate and return the gross pay. main() captures the return value in pay.

23: CalcTaxes() uses the gross pay to calculate and return the taxes. main() captures the return value in taxes.

24: The employee, gross pay, and taxes are sent to PrintResults() to be displayed on-screen.

25: Always return from main() to QuickWin.

26: A final brace ends all main() functions.

27: A line of asterisks helps to separate functions.

28: The definition (first line) of GetPayrollInput(). Receives three parameters: name by address, rate, and hours by reference.

29: All functions begin with an opening brace.

30: Comment to explain the function.

31: Call another function to get the employee name.

32: Call another function to get hours worked.

33: Call another function to get rate per hour.

34: Return to main() having passed data back via reference parameters.

35: A final brace ends a function definition.

36: A line of asterisks helps to separate functions.

37: The definition of GetInput(), which retrieves a string. It receives a const char array so that the calling program can send a literal to prompt the user.

38: All functions begin with an opening brace.

39: Use cout to output a prompt for user input.

40: cin.getline retrieves a whole line of text up to a maximum number of characters.

41: return to the calling function, GetPayrollInput.

42: A final brace ends a function definition.

43: A line of asterisks helps to separate functions.

44: The definition of GetInput() for a float. Receives a const char array so that the calling program can send literal for prompt.

45: All functions begin with an opening brace.

46: Use cout to output a prompt for user input.

47: cin >> retrieves a float.

48: return to the calling function, GetPayrollInput.

49: A final brace ends a function definition.

50: A line of asterisks helps to separate functions.

51: The definition of GetInput() for a float. Receives a const char array so that the calling program can send literal for prompt.

52: All functions begin with an opening brace.

53: Use cout to output a prompt for user input.

54: cin >> retrieves a float.

55: return to the calling function, GetPayrollInput.

56: A final brace ends a function definition.

57: A line of asterisks helps to separate functions.

58: Defines the function that calculates gross pay. This function receives a floating-point and an integer parameter passed by value.

59: Scatter comments throughout your code.

60: Returns the wages (the number of hours multiplied by the rate per hour).

61: A final brace ends all functions.

62: A line of asterisks helps to separate functions.

63: Defines the function that calculates taxes. Requires a float and the tax rate both passed by value, which can be defaulted (line 6).

64: Scatter comments throughout your code.

65: Returns the taxes to main(), which are simply the gross pay multiplied by the tax rate.

66: A final brace ends all functions.

67: A line of asterisks helps to separate functions.

68: Defines the function that prints the results, and requires a char array passed by address and two parameters passed by value.

69: Scatter comments throughout your code.

70: Ensure that two decimal places print.

71: Always show the decimal point.

72: Guard against scientific notation.

73: Prints the employee's gross pay.

74: The long cout is concluded.

75: Prints the employee's tax requirement.

76: Returns to main().

77: A final brace ends all functions.

---

6: Prototype all functions.

8: The tax rate is defaulted if rate is not present.

13: C++ distinguishes different overloaded functions by parameter data types.

16: Keep main() as simple as possible.

21: The function receives the variables by reference.

23: The tax rate parameter is not specified; therefore, the default is used.

31: Break down a complicated function into several easier steps by using function calls.

37: The passing of the prompt means that the function could be reused to get other values in the program.

44: By breaking down the function, each step is small and easy to understand.

58: You can return at most one value.

---

Contact reference@earthweb.com with questions or comments.
Copyright 1998 EarthWeb Inc., All rights reserved.
PLEASE READ THE ACCEPTABLE USAGE STATEMENT.
Copyright 1998 Macmillan Computer Publishing. All rights reserved.