This is a school assignment and I think it's nearly done, there are probably some parts that need straightening out, but at this point I'm just trying to get my program to compile correctly.

The program depends on an input file with sample data as follows:
1000 John 9.5 9.0 8.5 8.0 8.5 87.0 92.5 86.0
2000 Tom 10.0 6.7 10.0 10.0 10.0 100.0 100.0 100.0
3000 Alice 6.9 8.0 8.0 8.0 8.0 80.0 80.0 80.0

id, name, quiz1, quiz2, quiz3, quiz4, quiz5, midterm1, midterm2, final

Here is what I have so far:

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

//Function prototypes
void read_calcData(int id[], double average[], char grade[], string name[], int num_students, ifstream& in_file);

void printData(int id[], double average[], char grade[], string name[], int num_students);

void displayStats(double average[], int num_students, char grade[]);

void recordFinder(int id[], double average[], char grade[], string name[], int num_students, ifstream& in_file);

int main ()
{
	string name[30];
    int num_students, id[30];
    double average[30];
    char grade[30]; 
	ifstream in_file;

    read_calcData(id, average, grade, name, num_students, in_file);
    printData(id, average, grade, name, num_students);
    displayStats(average, num_students, grade);
    recordFinder(id, average, grade, name, num_students, in_file);

    return 0;
}

//Function reads data file and calculates average and grade of each student.
void read_calcData(int id[], double average[], char grade[], string name[], int num_students, ifstream& in_file)
{
	char input_file[30];
	double quiz1, quiz2, quiz3, quiz4, quiz5, midterm1, midterm2, final, worst_quiz;
    
	cout.setf(ios::fixed);
    cout.setf(ios::showpoint);
    cout.precision(2);

	cout << "Enter an input file: ";
    cin >> input_file;

    in_file.open(input_file);
   
    if (in_file.fail())
    {
        cout << "Sorry, there was an error opening the input file" << endl;
        exit (1);
    }

    char students[30];
	while(!in_file.getline(students,30).eofbit)
	{
			num_students++;
	}

    for (int i=0; i < num_students; i++)
    {
        in_file >> id[i] >> name[i] >> quiz1 >> quiz2 >> quiz3 >> quiz4 >> quiz5 >> midterm1 >> midterm2 >> final;

        if (quiz1 < quiz2 && quiz1 < quiz3 && quiz1 < quiz4 && quiz1 < quiz5)
        {
            worst_quiz = quiz1;
        }
        else if (quiz2 < quiz1 && quiz2 < quiz3 && quiz2 < quiz4 && quiz2 < quiz5)
        {
            worst_quiz = quiz2;
        }
        else if (quiz3 < quiz1 && quiz3 < quiz2 && quiz3 < quiz4 && quiz3 < quiz5)
        {
            worst_quiz = quiz3;
        }
        else if (quiz4 < quiz1 && quiz4 < quiz2 && quiz4 < quiz3 && quiz4 < quiz5)
        {
            worst_quiz = quiz4;
        }
        else
        {
            worst_quiz = quiz5;
        }

        average[i] = ((((quiz1+quiz2+quiz3+quiz4+quiz5-worst_quiz)*10)/4)*.2)+(((midterm1+midterm2)/2)*.4)+(final*.4);

        if (average[i] >= 90)
        {
            grade[i] = 'A';
        }
        else if (average[i] >=80)
        {
            grade[i] = 'B';
        }
        else if (average[i] >=70)
        {
            grade[i] = 'C';
        }
        else if (average[i] >=60)
        {
            grade[i] = 'D';
        }
        else
        {
            grade[i] = 'F';
        }
    }  
    return;
}

//Function displays student id, name, average, and grade.
void printData(int id[], double average[], char grade[], string name[], int num_students)
{
	
    int m;
    double hold;

    for (int i=0; i<=num_students-2; i++)
    {
        m = i;
        for (int j=i+1; j <= num_students-1; j++)
        {
            if (average[j] > average[m])
                m = j;
        }

        hold = average[m];
        average[m] = average[i];
        average[i] = hold;
    }

    cout << "---------------------------------------------------" << endl;
    cout << "     Individual Course Report" << endl;
    cout << "---------------------------------------------------" << endl;

    for (int i=0; i < num_students; i++)
    {
        cout << "  " << id[i] << " " << name[i] << " - " << average[i] << " " << grade[i] << endl;
    }

    cout << "---------------------------------------------------" << endl;

    return;
}


//Function displays statistics for students including number of students, class average, and a histogram illustrating grade distribution.
void displayStats(double average[], int num_students, char grade[])
{
	double average_all=0;
	int gradeA=0;
	char starsA=0;

	cout << " " << endl;
	cout << "---------------------------------------------------" << endl;
	cout << "     Statistics" << endl;
	cout << "---------------------------------------------------" << endl;
	cout << "  Number of Students: " << num_students << endl;
	for (int i=0; i< num_students; i++)
	{
		average_all += average[i];
	}
	average_all = average_all/num_students;

	cout << "  Average of All Students: " << average_all << endl;
	cout << "  Grade Distribution (histogram)" << endl;

	cout << "      A: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i] == 'A')
		{
		cout << "*";
		}
	}
	cout << endl;		
	
	cout << "      B: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i]=='B')
		{
			cout << "*";
		}
	}
	cout << endl;

	cout << "      C: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i]=='C')
		{
			cout << "*";
		}
	}
	cout << endl;

	cout << "      D: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i]=='D')
		{
			cout << "*";
		}
	}
	cout << endl;

	cout << "      F: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i]=='F')
		{
			cout << "*";
		}
	}
	cout << endl;
	cout << "---------------------------------------------------" << endl;
	cout << " " << endl;

	return;
}

//Function asks the user for a student id number and displays the student's id, name, average, and grade.
void recordFinder(int id[], double average[], char grade[], int num_students, string name[], ifstream& in_file)
{
	char option;
	int id2;

	for (int k=0; k<num_students; k++)
	{
		cout << "---------------------------------------------------" << endl;
		cout << "    Record Finder: Enter an id of a student: ";
		cin >> id2;
		
		for (int i=0; i<num_students; i++)
		{
			in_file >> id[i] >> name[i];

			if (id2=id[i])
			{
			cout << "---------------------------------------------------" << endl;
			cout << "    ID: " << id << endl;
			cout << "    Name: " << name << endl;
			cout << "    Average: " << average << " " << grade << endl;
			cout << "---------------------------------------------------" << endl;
			cout << "    Do you want to continue? (Y/N) ";
			cin >> option;
				if (option == 'n' || option == 'N')
				{
					cout << "---------------------------------------------------" << endl;
					cout << "    Done." << endl;
					return;
				}
			}
			if(id2 != id[i])
			{
			cout << "---------------------------------------------------" << endl;
			cout << "Fail to search. Id 1500 doesn’t exist." << endl;
			cout << "---------------------------------------------------" << endl;
			cout << "    Do you want to continue? (Y/N) ";
			cin >> option;
				if (option == 'n' || option == 'N')
				{
					cout << "---------------------------------------------------" << endl;
					cout << "    Done." << endl;
					return;
				}
			}
		}
	}
}

Edited 6 Years Ago by exospire: changed streams to call by reference, but now I have 2 errors

Solved a few problems, but now my program won't correctly count the num_students in my program.

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

//Function prototypes
void read_calcData(int id[], double average[], char grade[], string name[], int num_students, ifstream& in_file);

void printData(int id[], double average[], char grade[], string name[], int num_students);

void displayStats(double average[], int num_students, char grade[]);

void recordFinder(int id[], double average[], char grade[], string name[], int num_students, ifstream& in_file);

int main ()
{
	string name[30];
    int num_students=0, id[30];
    double average[30];
    char grade[30]; 
	ifstream in_file;

    read_calcData(id, average, grade, name, num_students, in_file);
    printData(id, average, grade, name, num_students);
    displayStats(average, num_students, grade);
    recordFinder(id, average, grade, name, num_students, in_file);

    return 0;
}

//Function reads data file and calculates average and grade of each student.
void read_calcData(int id[], double average[], char grade[], string name[], int num_students, ifstream& in_file)
{
	char input_file[30];
	double quiz1, quiz2, quiz3, quiz4, quiz5, midterm1, midterm2, final, worst_quiz;
    
	cout.setf(ios::fixed);
    cout.setf(ios::showpoint);
    cout.precision(2);

	cout << "Enter an input file: ";
    cin >> input_file;

    in_file.open(input_file);
   
    if (in_file.fail())
    {
        cout << "Sorry, there was an error opening the input file" << endl;
        exit (1);
    }

    char students[30];
	while(!in_file.getline(students,30).eofbit)
	{
			num_students++;
	}

    for (int i=0; i < num_students; i++)
    {
        in_file >> id[i] >> name[i] >> quiz1 >> quiz2 >> quiz3 >> quiz4 >> quiz5 >> midterm1 >> midterm2 >> final;

        if (quiz1 < quiz2 && quiz1 < quiz3 && quiz1 < quiz4 && quiz1 < quiz5)
        {
            worst_quiz = quiz1;
        }
        else if (quiz2 < quiz1 && quiz2 < quiz3 && quiz2 < quiz4 && quiz2 < quiz5)
        {
            worst_quiz = quiz2;
        }
        else if (quiz3 < quiz1 && quiz3 < quiz2 && quiz3 < quiz4 && quiz3 < quiz5)
        {
            worst_quiz = quiz3;
        }
        else if (quiz4 < quiz1 && quiz4 < quiz2 && quiz4 < quiz3 && quiz4 < quiz5)
        {
            worst_quiz = quiz4;
        }
        else
        {
            worst_quiz = quiz5;
        }

        average[i] = ((((quiz1+quiz2+quiz3+quiz4+quiz5-worst_quiz)*10)/4)*.2)+(((midterm1+midterm2)/2)*.4)+(final*.4);

        if (average[i] >= 90)
        {
            grade[i] = 'A';
        }
        else if (average[i] >=80)
        {
            grade[i] = 'B';
        }
        else if (average[i] >=70)
        {
            grade[i] = 'C';
        }
        else if (average[i] >=60)
        {
            grade[i] = 'D';
        }
        else
        {
            grade[i] = 'F';
        }
    }  
    return;
}

//Function displays student id, name, average, and grade.
void printData(int id[], double average[], char grade[], string name[], int num_students)
{
	
    int m;
    double hold;

    for (int i=0; i<=num_students-2; i++)
    {
        m = i;
        for (int j=i+1; j <= num_students-1; j++)
        {
            if (average[j] > average[m])
                m = j;
        }

        hold = average[m];
        average[m] = average[i];
        average[i] = hold;
    }

    cout << "---------------------------------------------------" << endl;
    cout << "     Individual Course Report" << endl;
    cout << "---------------------------------------------------" << endl;

    for (int i=0; i < num_students; i++)
    {
        cout << "  " << id[i] << " " << name[i] << " - " << average[i] << " " << grade[i] << endl;
    }

    cout << "---------------------------------------------------" << endl;

    return;
}


//Function displays statistics for students including number of students, class average, and a histogram illustrating grade distribution.
void displayStats(double average[], int num_students, char grade[])
{
	double average_all=0;
	int gradeA=0;
	char starsA=0;

	cout << " " << endl;
	cout << "---------------------------------------------------" << endl;
	cout << "     Statistics" << endl;
	cout << "---------------------------------------------------" << endl;
	cout << "  Number of Students: " << num_students << endl;
	for (int i=0; i< num_students; i++)
	{
		average_all += average[i];
	}
	average_all = average_all/num_students;

	cout << "  Average of All Students: " << average_all << endl;
	cout << "  Grade Distribution (histogram)" << endl;

	cout << "      A: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i] == 'A')
		{
		cout << "*";
		}
	}
	cout << endl;		
	
	cout << "      B: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i]=='B')
		{
			cout << "*";
		}
	}
	cout << endl;

	cout << "      C: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i]=='C')
		{
			cout << "*";
		}
	}
	cout << endl;

	cout << "      D: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i]=='D')
		{
			cout << "*";
		}
	}
	cout << endl;

	cout << "      F: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i]=='F')
		{
			cout << "*";
		}
	}
	cout << endl;
	cout << "---------------------------------------------------" << endl;
	cout << " " << endl;

	return;
}

//Function asks the user for a student id number and displays the student's id, name, average, and grade.
void recordFinder(int id[], double average[], char grade[], string name[], int num_students, ifstream& in_file)
{
	char option;
	int id2;

	for (int k=0; k<num_students; k++)
	{
		cout << "---------------------------------------------------" << endl;
		cout << "    Record Finder: Enter an id of a student: ";
		cin >> id2;
		
		for (int i=0; i<num_students; i++)
		{
			in_file >> id[i] >> name[i];

			if (id2=id[i])
			{
			cout << "---------------------------------------------------" << endl;
			cout << "    ID: " << id << endl;
			cout << "    Name: " << name << endl;
			cout << "    Average: " << average << " " << grade << endl;
			cout << "---------------------------------------------------" << endl;
			cout << "    Do you want to continue? (Y/N) ";
			cin >> option;
				if (option == 'n' || option == 'N')
				{
					cout << "---------------------------------------------------" << endl;
					cout << "    Done." << endl;
					return;
				}
			}
			if(id2 != id[i])
			{
			cout << "---------------------------------------------------" << endl;
			cout << "Fail to search. Id 1500 doesn’t exist." << endl;
			cout << "---------------------------------------------------" << endl;
			cout << "    Do you want to continue? (Y/N) ";
			cin >> option;
				if (option == 'n' || option == 'N')
				{
					cout << "---------------------------------------------------" << endl;
					cout << "    Done." << endl;
					return;
				}
			}
		}
	}
}

num_students is a local variable in main function which is initalized to zero. After calling the function read_calcData the variable num_students will be zero because you have not passed the address of num_students to the function read_calcData where the number of students is calculated.

The num_students variable is local to read_calcData the variable looses its scope as soon as the function read_calcData is executed.

num_students is a local variable in main function which is initalized to zero. After calling the function read_calcData the variable num_students will be zero because you have not passed the address of num_students to the function read_calcData where the number of students is calculated.

The num_students variable is local to read_calcData the variable looses its scope as soon as the function read_calcData is executed.

How do I pass the address of num_students to the function, and how do I make num_students retain its value when it gets displayed in my displayStats function? Do I have to include a & and call by reference? I tried this but it just gave me more errors.

Alright I got everything to work so far except for the recordFinder function... this is what my program displays:

Record Finder: Enter an id of a student: 2000
---------------------------------------------------
ID: 0012FB08
Name: 0012FB94
Average: 0012FA10 BABÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌ

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

//Function prototypes
void read_calcData(int id[], double average[], char grade[], string name[], int & num_students, ifstream& in_file, char input_file[]);

void printData(int id[], double average[], char grade[], string name[], int num_students);

void displayStats(double average[], int num_students, char grade[]);

void recordFinder(int id[], double average[], char grade[], string name[], int num_students, ifstream& in_file);

int main ()
{
	string name[30];
    int num_students=0, id[30];
    double average[30];
    char grade[30]; 
	ifstream in_file;
	char input_file[30];


    read_calcData(id, average, grade, name, num_students, in_file, input_file);
    printData(id, average, grade, name, num_students);
    displayStats(average, num_students, grade);
    recordFinder(id, average, grade, name, num_students, in_file);

    return 0;
}

//Function reads data file and calculates average and grade of each student.
void read_calcData(int id[], double average[], char grade[], string name[], int & num_students, ifstream& in_file, char input_file[])
{
	
	double quiz1, quiz2, quiz3, quiz4, quiz5, midterm1, midterm2, final, worst_quiz;
    
	cout.setf(ios::fixed);
    cout.setf(ios::showpoint);
    cout.precision(2);

	cout << "Enter an input file: ";
    cin >> input_file;

    in_file.open(input_file);
   
    if (in_file.fail())
    {
        cout << "Sorry, there was an error opening the input file" << endl;
        exit (1);
    }
	
	int i=0;
     while (in_file >> id[i] >> name[i] >> quiz1 >> quiz2 >> quiz3 >> quiz4 >> quiz5 >> midterm1 >> midterm2 >> final)
	 {
        if (quiz1 < quiz2 && quiz1 < quiz3 && quiz1 < quiz4 && quiz1 < quiz5)
        {
            worst_quiz = quiz1;
        }
        else if (quiz2 < quiz1 && quiz2 < quiz3 && quiz2 < quiz4 && quiz2 < quiz5)
        {
            worst_quiz = quiz2;
        }
        else if (quiz3 < quiz1 && quiz3 < quiz2 && quiz3 < quiz4 && quiz3 < quiz5)
        {
            worst_quiz = quiz3;
        }
        else if (quiz4 < quiz1 && quiz4 < quiz2 && quiz4 < quiz3 && quiz4 < quiz5)
        {
            worst_quiz = quiz4;
        }
        else
        {
            worst_quiz = quiz5;
        }

        average[i] = ((((quiz1+quiz2+quiz3+quiz4+quiz5-worst_quiz)*10)/4)*.2)+(((midterm1+midterm2)/2)*.4)+(final*.4);

        if (average[i] >= 90)
        {
            grade[i] = 'A';
        }
        else if (average[i] >=80)
        {
            grade[i] = 'B';
        }
        else if (average[i] >=70)
        {
            grade[i] = 'C';
        }
        else if (average[i] >=60)
        {
            grade[i] = 'D';
        }
        else
        {
            grade[i] = 'F';
        }
		i++;
    }  
	 num_students = i;
    return;
}

//Function displays student id, name, average, and grade.
void printData(int id[], double average[], char grade[], string name[], int num_students)
{
	
    int m;
    double hold;

    for (int i=0; i<=num_students-2; i++)
    {
        m = i;
        for (int j=i+1; j <= num_students-1; j++)
        {
            if (average[j] > average[m])
                m = j;
        }

        hold = average[m];
        average[m] = average[i];
        average[i] = hold;
    }

    cout << "---------------------------------------------------" << endl;
    cout << "     Individual Course Report" << endl;
    cout << "---------------------------------------------------" << endl;

    for (int i=0; i < num_students; i++)
    {
        cout << "  " << id[i] << " " << name[i] << " - " << average[i] << " " << grade[i] << endl;
    }

    cout << "---------------------------------------------------" << endl;

    return;
}


//Function displays statistics for students including number of students, class average, and a histogram illustrating grade distribution.
void displayStats(double average[], int num_students, char grade[])
{
	double average_all=0;
	int gradeA=0;
	char starsA=0;

	cout << " " << endl;
	cout << "---------------------------------------------------" << endl;
	cout << "     Statistics" << endl;
	cout << "---------------------------------------------------" << endl;
	cout << "  Number of Students: " << num_students << endl;
	for (int i=0; i< num_students; i++)
	{
		average_all += average[i];
	}
	average_all = average_all/num_students;

	cout << "  Average of All Students: " << average_all << endl;
	cout << "  Grade Distribution (histogram)" << endl;

	cout << "      A: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i] == 'A')
		{
		cout << "*";
		}
	}
	cout << endl;		
	
	cout << "      B: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i]=='B')
		{
			cout << "*";
		}
	}
	cout << endl;

	cout << "      C: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i]=='C')
		{
			cout << "*";
		}
	}
	cout << endl;

	cout << "      D: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i]=='D')
		{
			cout << "*";
		}
	}
	cout << endl;

	cout << "      F: ";
	for (int i=0; i<num_students; i++)
	{
		if (grade[i]=='F')
		{
			cout << "*";
		}
	}
	cout << endl;
	cout << "---------------------------------------------------" << endl;
	cout << " " << endl;

	return;
}

//Function asks the user for a student id number and displays the student's id, name, average, and grade.
void recordFinder(int id[], double average[], char grade[], string name[], int num_students, ifstream& in_file)
{
	char option;
	int id2;

	for (int k=0; k<num_students; k++)
	{
		cout << "---------------------------------------------------" << endl;
		cout << "    Record Finder: Enter an id of a student: ";
		cin >> id2;
		
		for (int i=0; i<num_students; i++)
		{
			in_file >> id[i] >> name[i];

			if (id2=id[i])
			{
			cout << "---------------------------------------------------" << endl;
			cout << "    ID: " << id << endl;
			cout << "    Name: " << name << endl;
			cout << "    Average: " << average << " " << grade << endl;
			cout << "---------------------------------------------------" << endl;
			cout << "    Do you want to continue? (Y/N) ";
			cin >> option;
				if (option == 'n' || option == 'N')
				{
					cout << "---------------------------------------------------" << endl;
					cout << "    Done." << endl;
					return;
				}
			}
			if(id2 != id[i])
			{
			cout << "---------------------------------------------------" << endl;
			cout << "Fail to search. Id 1500 doesn’t exist." << endl;
			cout << "---------------------------------------------------" << endl;
			cout << "    Do you want to continue? (Y/N) ";
			cin >> option;
				if (option == 'n' || option == 'N')
				{
					cout << "---------------------------------------------------" << endl;
					cout << "    Done." << endl;
					return;
				}
			}
		}
	}
}

The variable

num_students

being pointer in the function

read_calcData

to acces the value pointed by this pointer you have to dereference the pointer.

Start with a function and debug to see if the values that you get are the ones which are expected.

This question has already been answered. Start a new discussion instead.