How to read in specific numbers from a txt file C++ - c++

Question

The problem I am having is that I do not know how to read a specific number out of a text file that was created and had values entered into it earlier in the program.
I was hoping to use a nested loop statement for reading in the values after the values of the quizes are read in I need to add up the values and average them out and this needs to happen multiple times
#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
using namespace std;
int main()
{
string StudentGrades;
int studentID;
double quiz1;
double quiz2;
double quiz3;
double quiz4;
double total=0;
double choice;
ofstream outFile;
cout << "Enter student ID number, Quiz 1 Grade, Quiz 2 Grade , Quiz 3 Grade, Quiz 4 Grade" << endl;
outFile.open("StudentGrades.txt");
//while (outFile.open)
//{
for (int x = 0; x < 4; x++)
{
cout << "Enter student ID: ";
cin >> studentID;
cout << "Enter quiz grade 1: ";
cin >> quiz1;
//cout << quiz1;
cout << "Enter quiz grade 2: ";
cin >> quiz2;
//cout << quiz2;
cout << "Enter quiz grade 3: ";
cin >> quiz3;
//cout << quiz3;
cout << "Enter quiz grade 4: ";
cin >> quiz4;
//cout << quiz4;
cout << endl;
//outFile.open("StudentGrades.txt");
if (outFile.is_open())
{
cout << "inside if/else outFile" << endl;
//outFile << "File successfully open";
outFile << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
}
else
{
cout << "Error opening file";
}
cout << "Enter 0 for no more students. Enter 1 for more students." << endl;
cin >> choice;
if (choice == 1)
continue;
if (choice == 0)
{
outFile.close();
break;
}
}
//}
//declaring file and opening it
ifstream inFile;
inFile.open("StudentGrades.txt");
while (inFile>>studentID)
{
cout << studentID<< quiz1 <<quiz2<<quiz3<<quiz4<< endl;
}
system("pause");
return (0);
}

Answer 1

You are not reading all the fields from the input file, you are reading just the studentID.
while (inFile>>studentID)
{
cout << studentID<< quiz1 <<quiz2<<quiz3<<quiz4<< endl;
}
Try:
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
cout << studentID << quiz1 << quiz2 << quiz3 << quiz4 << endl;
}
Update
Below is my suggestion for a refactored program. It's good to create functions that perform specific tasks and then call them from a higher level function instead of jamming them all in one large function.
#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
using namespace std;
void saveStudentData(string const& filename)
{
int studentID;
double quiz1;
double quiz2;
double quiz3;
double quiz4;
// Use int type for choice, not double
int choice;
ofstream outFile(filename);
if (!outFile.is_open())
{
// Problem opening file.
cout << "Error opening file";
return;
}
cout << "Enter student ID number, Quiz 1 Grade, Quiz 2 Grade , Quiz 3 Grade, Quiz 4 Grade" << endl;
for (int x = 0; x < 4; x++)
{
cout << "Enter student ID: ";
cin >> studentID;
cout << "Enter quiz grade 1: ";
cin >> quiz1;
cout << "Enter quiz grade 2: ";
cin >> quiz2;
cout << "Enter quiz grade 3: ";
cin >> quiz3;
cout << "Enter quiz grade 4: ";
cin >> quiz4;
cout << endl;
outFile << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
cout << "Enter 0 for no more students. Enter 1 for more students." << endl;
cin >> choice;
if (choice == 0)
{
break;
}
}
}
void readStudentData(string const& filename)
{
int studentID;
double quiz1;
double quiz2;
double quiz3;
double quiz4;
double total=0;
ifstream inFile(filename);
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
total = (quiz1 + quiz2 + quiz3 + quiz4);
cout << studentID << " " << quiz1 << " " << quiz2
<< " " << quiz3 << " " << quiz4 << " " << total << endl;
}
}
int main()
{
string filename("StudentGrades.txt");
saveStudentData(filename);
readStudentData(filename);
return (0);
}