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  1. //Andres Guzman CSC5 Chapter 6, P. 373, #15
  2. //
  3. /*******************************************************************************
  4. *
  5. *  CALCULATE POPULATION
  6. * ______________________________________________________________________________
  7. * This program will calculate a population after an inputed set of years
  8. *
  9. * Computation:
  10. *
  11. * N = P + BP - BP
  12. * ______________________________________________________________________________
  13. * INPUT
  14. *
  15. * pop = Input for population
  16. * birth = Input for birth rate
  17. * death = Input for death rate
  18. * years = Input for number of years
  19. * OUTPUT
  20. * newpop = New population
  21. *******************************************************************************/
  22. #include <iostream>
  23. #include <iomanip>
  24. using namespace std;
  25.  
  26. int pop;		//Global Variable
  27. double birth;	//Global Variable
  28. double death;	//Global Variable
  29. int years;		//Global Variable
  30.  
  31. double population();	//function prototype
  32.  
  33. int main ()
  34. {
  35. 	cout << "\tPopulation" << endl;
  36. 	cout << "Population Starting Size: ";
  37. 	cin >> pop;
  38. //
  39. //While loop to validate population input
  40. 	while(pop < 2)	//pop cannot be less than 2
  41. 	{
  42. 		cout << "Invalid Starting Size." << endl;
  43. 		cout << "Population Starting Size: ";
  44. 		cin >> pop;
  45. 	}
  46. 	cout << "\nAnnual Birth Rate: ";
  47. 	cin >> birth;
  48. //
  49. //While loop to validate birth rate input
  50. 	while (birth < 0)	//birth cannot be less than 0
  51. 	{
  52. 		cout << "Invalid Rate." << endl;
  53. 		cout << "Annual Birth Rate: ";
  54. 		cin >> birth;
  55. 	}
  56. 	cout << "\nAnnual Death Rate: ";
  57. 	cin >> death;
  58. //
  59. //While loop to validate death rate input
  60. 	while (death < 0)	//death cannot be less than 0
  61. 	{
  62. 		cout << "Invalid Rate." << endl;
  63. 		cout << "Annual Death Rate: ";
  64. 		cin >> death;
  65. 	}
  66. 	cout << "\nYears to Display: ";
  67. 	cin >> years;
  68. 	cout << endl;
  69. //
  70. //While loop to validate years input
  71. 	while (years < 1) // Years cannot be less than 1
  72. 	{
  73. 		cout << "Invalid Years." << endl;
  74. 		cout << "Years to Display: ";
  75. 		cin >> years;
  76. 		cout << endl;
  77. 	}
  78. //
  79. //Calling function
  80. 	population();	//Function Call
  81. }
  82.  
  83. /*******************************************************************************
  84.  * Creating defintion for function population. It will use the inputs from the 
  85.  * global variables to caluclate the new population using the formula inside and
  86.  * then will output a loop with the result for each year.
  87.  ******************************************************************************/
  88. double population()
  89. {
  90. 	 double newpop = pop;	//Transfers pop value to newpop for easier 
  91. 							//calculation.
  92.  
  93. 	 for (int i = 1; i <= years; i++)	//For loop to loop each inputed year
  94. 	 {
  95. 		 newpop =  newpop + (birth * newpop) - (death * newpop); //formula for 
  96. 																//new population
  97. //
  98. //If statement to remove any negative results
  99. 		 if(newpop < 0) //
  100. 		 {
  101. 			 newpop = 0;	//If its less than 0, then the value becomes 0
  102. 		 }
  103. //
  104. //Outputting results and allowing for decimal points
  105. 		 cout << fixed << setprecision(2) << "Year " << i << ": ";
  106. 		 cout << newpop << endl;
  107. 	 }
  108. 	 return newpop;	//returns the value of newpop
  109. }
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	Population
Population Starting Size: 
Annual Birth Rate: 
Annual Death Rate: 
Years to Display: 
Year 1: 2.00
Year 2: 2.00
https://ideone.com/IsBypZ
Chapter 6 #15(Needs documentation)
language:
C++ (gcc 8.3)
created:
6 days ago
visibility:
public

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