This C++ program will calculate the average of 4 grades by using weight calculation. It will then display the average and give the user a chance to review the grades.

1. #include <cstdlib>
2. #include <iostream>
4. using namespace std;
6. bool isitvalid(double[]);
7. bool printarray(double[], int);
9. int main()
10. {
11.  // To hold the weights and the grades
12.  double weights[4];
13.  double grades[4];
14.  // To hold the averages
15.  double avrGrade = 0;
16.  double avrClassGrade = 0;
17.  int numOfStudents = 0;
18.  char respChar = ‘N’;
19.  int revGrade;
20.  bool anotherStudent = false;
21.  // Do until the user decides not to enter anymore students
22.  do
23.  {
24.  // Loop for the user to enter the weight
25.  for(int i = 0; i < 4; i++)
26.  {
27.  cout << “Please enter weight for grade (e.g. 0.3) #” << i + 1 << “: “;
28.  cin >> weights[i];
29.  }
30.  // Loop for the user to enter the grades (until all are valid)
31.  do
32.  {
33.  for(int i = 0; i < 4; i++)
34.  {
35.  cout << “Please enter grade #” << i + 1 << “: “;
36.  cin >> grades[i];
37.  }
38.  }
39.  while(isitvalid(grades) == false);
41.  // Loop to calculate the average
42.  for(int i = 0; i < 4; i++)
43.  {
44.                 avrGrade += weights[i] * grades[i];
45.  }
46.  // Show the final grade
47.  cout << “The final grade is: ” << avrGrade << “\n“;
48.  // If the user wants to review the grades, call the printarray() function
49.  cout << “Enter the number of grades you want to review (0 to continue): “;
50.  cin >> revGrade;
51.  if(revGrade > 0)
52.  {
53.                     printarray(grades, revGrade);
54.  }
55.  cout << “Would you like to enter another student? Type Y for Yes anything else for No: “;
56.  cin >> respChar;
57.  // Holds the average class grade
58.         avrClassGrade += avrGrade;
59.         numOfStudents++;
60.  }
61.  while(respChar == ‘Y’);
62.  // When the loops and conditions are all complete show the class average
63.  cout << “\nThe class average is ” << avrClassGrade / numOfStudents << “\n“;
64.  system(“PAUSE”);
65.  return 0;
66. }
68. bool isitvalid(double grades[])
69. {
70. // Will be set to true if a bad grade is found
71. bool badGrade = false;
72. for(int i = 0; i < 4; i++)
73. {
74. if(grades[i] < 0 || grades[i] > 100)
75. {
76.                   badGrade = true;
77. }
78. }
79. if(badGrade == true)
80. {
81. return false;
82. }
83. else
84. {
85. return true;
86. }
87. }
89. bool printarray(double grades[], int numOfGrades)
90. {
91. // Loop through the number of grades the user has decided to review and show them
92. for(int i = 0; i < numOfGrades; i++)
93. {
94. cout << “Grade #” << i + 1 << ” is ” << grades[i] << “\n“;
95. }
96. }