I have a problem that I have not been able to figure out with this assignment. The idea is to write a grading program that will calculate the letter grade, and average while also giving exam scores for 5 students, each student has 4 exams. I have built it up to this and even viewed a similar assignment posted but didn't find that helpful. I have gone through the book which also isn't very helpful in this regard. I am receiving errors regarding the highlighted sections that deal with processing the file data into the program. Error code in Visual Studio LNK1120:1 unresolved externals. If I remove "student.input(input, thisStudent);" this bit of code the program will run but with garbage values and that is where hopefully someone can help me with. How can I properly direct the data from a file into exam1-4. Am I missing something? If I can get the program to run with correct values I should be able figure out the rest. Thanks in advance.

#include <iostream>
#include <fstream> // I/O
#include <iomanip> // For setw()
using namespace std;

ofstream     outputfile("output.txt");     // Output file

// Defined Constants
const int    MAX_FILE_NAME = 35;            // Max space allocated for file name
const int CLASS_SIZE = 5;
class StudentRecord
{

public:

    **void input(ifstream& input,int studentid);** // reads exam scores for this student 
    void computeGrade(); //calculates the numeric average and letter grade. 
    void output(); //outputs the student record.
    //outputs student record

private:
    int studentNumber;
    double exam1;
    double exam2;
    double exam3;
    double exam4;
    double average;
    char grade;
};

void open_input(ifstream& input, char name[]); // Get file name & Open file
void process_file(ifstream& input);            // Read each value & process 

int main()
{
    //StudentRecord student1, student2, student3, 
    //  student4, student5;

    char again;             // Does user want to go through loop again?
    char file_name[MAX_FILE_NAME + 1]; // Name of file to be processed
   ifstream input_numbers;            // For working with input file

   cout << "This program will calculate student grades.\n"
         << "It will give exam scores and averages with letter grade.\n";

   system("pause"); // Hold message on screen until key is pressed

   do 
   {  
      system("cls");                           // Clear screen
      open_input(input_numbers, file_name);    // Get file name & open file
      process_file(input_numbers);             // Process values in file
      input_numbers.close();                   // Close file

      cout << "\nDo you want to process another file (Y/N)? ";
      cin >> again;
      cin.ignore(256, '\n');  // Remove Enter key from keyboard buffer

   } while ( again == 'y' || again == 'Y'); 

   cout << "\nEnd of Program!" << endl;
   outputfile << "\n\nThanks for using Grade Pro!\f"; 
   outputfile.close();

   return 0; 
}  // End of main()

void process_file(ifstream& input) 
// Parameters: Variable for file reference
// Returns:    None
// Calls:      Invoice::set_merchandise_value(), Invoice::output()

{  
    double thisStudent = 0;              // Merchandise value from file

    StudentRecord student = StudentRecord();    // Record for student

    while (thisStudent++ < CLASS_SIZE)
    {
        **student.input(input, thisStudent);**
        student.computeGrade();
        student.output();
    } // End of process_file()
}
void open_input(ifstream& input, char name[]) //Open file, exit on error
// Parameters: Variables for input file reference nad input file name
// Returns:    None
// Calls:      None
{  int count = 0;             // Count number of tries
   do // Continue until we get a valid file name and can open file
   {  count++;
      if (count != 1)  // Issue error message if we are trying again.
      {  cout << "\n\aInvalid file name or file does not exist. Please try again." 
              << endl;
      }
      cout << "\nEnter the input file name (maximum of " << MAX_FILE_NAME
           << " characters please)\n:> ";
      cin.get(name, MAX_FILE_NAME + 1);// Gets at most MAX_FILE_NAME characters
      cin.ignore(256, '\n');           // Remove Enter key from keyboard buffer
      input.clear();                   // Clear all error flags, if any, from prev try
      input.open(name,ios_base::in); // Open only if file exists
   } while (input.fail() );            // If can't open file, try again
} // End of open_input()

void StudentRecord::computeGrade()
{

    double average; 
    average = (exam1+exam2+exam3+exam4)/4;

    //Letter grade: A => 90 > B => 80 > C => 70 > D => 60 > F
    if(average>=90)
        grade = 'A';
    else if(average<90 && average>=80)
        grade = 'B';
    else if(average<80 && average>=70)
        grade = 'C';
    else if(average<70 && average>=60)
        grade = 'D';
    else if(average<60)
        grade = 'F';
}
void StudentRecord::output()
{
    cout << "\n\nExam1: " << setw(8) << exam1 << endl;
   cout <<      "Exam2: " << setw(8) << exam2 << endl;
   cout <<      "Exam3: " << setw(8) << exam3 << endl;
   cout <<      "Exam4: " << setw(8) << exam4 << endl;
   cout <<      "Avg:   " << setw(8) << average<< endl;
   cout <<      "Grade: " << setw(8) << grade << endl;
}

Big problem, you haven't provided an implementation for void input(ifstream& input,int studentid);

Wow thanks vmanes... I really should have seen that one.

Still trying to figure out the second part of my problem; dividing the data input between exams1-4. If someone could point me in the right direction for that bit of code it would be awsome.

Ok I came up with this for the implementation for void StudentRecord::input(ifstream& input,int studentid) but how do I pass the values that go into value to the objects exam1, exam2, exam3, and exam4. The values get to this part but I am at a lost of how to initialize those values to exam's 1-4. The input file is simply a set of 20 scores, 4 scores to each student. I am fairly new to this and could use all the help I can get on this one. Thanks.

void StudentRecord::input(ifstream& input,int studentid)
{
    double value;              // Value from file
   double sum = 0;
   double count = 0;
   while (input >> value)
   {  
      sum += value;
      count++;
   }

}

I got it solved. But a funny quirk with the average. It would calculate but would not pass through to output but all the exam scores passed through no problem; however it did work to evaluate to a letter grade. I ended up just re-posting the equation in the output function.

Solved by assigning the studentNumber to the studentid and inserted the data to exam1, exam2, etc.