C++ Output Errors - c++

Question

The output for this program, thanks to you guys, is fixed. Except for the studentNumber. I read the comment that I never set a value to it and that confused me.
void process_file(ifstream& input)
{
int thisStudent = 0;
StudentRecord student = StudentRecord();
while (thisStudent++ < CLASS_SIZE)
{
student.input(input, thisStudent);
student.computeGrade();
student.output();
}
}
would this not set studentNumber equal to 0 then add +1 every time it runs through the loop.
// Author:
// Assignment 8
#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
ofstream outputfile("output.txt");
const int MAX_FILE_NAME = 35;
const int CLASS_SIZE = 5;
class StudentRecord
{
public:
void input( ifstream& input,int studentid);
void computeGrade();
void output();
private:
int studentNumber;
double exam1;
double exam2;
double exam3;
double exam4;
double average;
char grade;
};
void open_input(ifstream& input, char name[]);
void process_file(ifstream& input);
int main()
{ char again;
char file_name[MAX_FILE_NAME + 1];
ifstream input_numbers;
cout << "This program can calculate the exam average and grade for\n"
<< "each student.\n" << endl;
system("pause");
do
{
system("cls");
open_input(input_numbers, file_name);
process_file(input_numbers);
input_numbers.close();
cout << "\nDo you want to process another file (Y/N)? ";
cin >> again;
cin.ignore(256, '\n');
} while ( again == 'y' || again == 'Y');
cout << "\nEnd of Program!" << endl;
outputfile << "\n\nThanks for using GradeCalc!\f";
outputfile.close();
return 0;
}
void process_file(ifstream& input)
{
int thisStudent = 0;
StudentRecord student = StudentRecord();
while (thisStudent++ < CLASS_SIZE)
{
student.input(input, thisStudent);
student.computeGrade();
student.output();
}
}
void open_input(ifstream& input, char name[])
{ int count = 0;
do
{ count++;
if (count != 1)
{ 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);
cin.ignore(256, '\n');
input.clear();
input.open(name,ios_base::in);
} while (input.fail() );
}
void StudentRecord::input(ifstream& input, int studentid)
{
input >> exam1 >> exam2 >> exam3 >> exam4;
}
void StudentRecord::computeGrade()
{
average = (exam1 + exam2 + exam3 + exam4) / 4 ;
if (average >= 90)
grade = 'A';
else if (average >= 80)
grade = 'B';
else if (average >= 70)
grade = 'C';
else if (average >= 60)
grade = 'D';
else if (average < 60)
grade = 'F';
}
void StudentRecord::output()
{
cout << "\n\nThe record for student number:" << setw(8) << studentNumber << endl;
cout << "The exam grades are:" << setw(8) << exam1 << exam2 << exam3 << exam4 << endl;
cout << "The numeric average is:" << setw(8) << average << endl;
cout << "and the letter grade assigned is:" << setw(8) << grade << endl;
}

Answer 1

Well, studentNumber is garbage because you never put a value in it. So it just has whatever happened to already be in memory at that location.
The exam grades print out wrong because commas in C++ don't do what you think they do, and that's also why adding an endl; to it gives you an error.
The formatting I'm going to let you work out for yourself. You should consider reading up on output or at least doing some trial and error.

Answer 2

One of the errors is that instead of this:
cout << "The exam grades are:" << setw(8) << exam1, exam2, exam3, exam4;
I think you mean this:
cout << "The exam grades are:" << setw(8) << exam1 << exam2 << exam3 << exam4 << endl;

Answer 3

CLASS_SIZE is defined as 5, so this loop:
while (thisStudent++ < CLASS_SIZE)
will iterate 6 times.
Also
cout << "The exam grades are:" << setw(8) << exam1, exam2, exam3, exam4;
This outputs exam1, and then evaluates and does nothing with the rest of the variables.

Answer 4

70 80 90 95 95 85 90 80 75 85 70 80 55 85 50 70 45 50 40 35
does it have the spaces? If yes, you need to ignore them. input >> exam1 >> exam2 >> exam3 >> exam4; would load space into one of the exam variables.
-- edit for MooingDuck --
#include <iostream>
#include <sstream>
using namespace std;
int main() {
cout << "main() ENTRY" << endl;
stringstream s1(ios_base::in | ios_base::out),
s2(ios_base::in | ios_base::out);
int i = -1;
s1 << "111 222";
s1 >> i; cout << i << endl;
s1 >> i; cout << i << endl;
s2 << "111 222";
s2 >> noskipws;
s2 >> i; cout << i << endl;
s2 >> i; cout << i << endl;
return 0;
}
Output:
main() ENTRY
111
222
111
0