How to display all the data I entered into my text file? - c++

Question

The following is a code to enter some details of students into a text file and from the main menu, the user can display them using option 2.
My problem is in the section where it should display all the "Taken Courses by student".
When I choose to display all data, the "mentioned section using the for loop only display the last value I enter when writing to the file.
How can I make it display all my entries?
The issue is under the showdata and displaydata functions.
//Project on Student Management
#include<iostream>
#include<fstream>
#include<iomanip>
#include<stdlib.h>
using namespace std;
class Student
{
int id;
int year;
char grade[50];
float cgpa;
int NumberOfcourses;
char courseName[100];
char academic_advisor[100];
char status[100];
public:
void getData();
void showData();
int getID(){return id;}
}s;
void Student::getData()
{
cout<<"\n\nEnter Student Details......\n";
cout<<"Enter ID No. : "; cin>>id;
cout << "Enter Intake Year of the Student: "; cin >> year;
cout << "Enter number of Taken courses: ";
cin >> NumberOfcourses;
for(int a=1; a<=s.NumberOfcourses; a++)
{
cout<<"\nEnter Subject Name: ";
cin.ignore();
cin.getline(courseName, 100);
cout << "Enter Grade of Subject: ";
cin >> grade;
cout<<"\nEnter Subject Status: ";
cin.ignore();
cin.getline(status, 100);
}
cout << "Enter student CGPA: ";
cin >> s.cgpa;
cout << endl;
cout << "Enter Name of Academic Advisor of Student: "; cin.ignore();
cin.getline(s.academic_advisor, 100);
}
void Student::showData()
{
cout << "\n\n.......Student Details......\n";
cout << "ID No. : " << id << endl;
cout << "Intake Year : " << year << endl;
cout << "Subjects Taken in Previous Semester : " << endl;
for(int t=1; t<=NumberOfcourses; t++)
{
cout << "\t" << courseName << ": " << grade << " ("<< status << ") ";
cout << endl;
}
cout << "CGPA : " << cgpa << endl;
cout << "Name of academic advisor of Student : " << academic_advisor << endl;
cout << endl;
}
void addData()
{
ofstream fout;
fout.open("Students.txt", ios::out|ios::app);
s.getData();
fout.write((char*)&s,sizeof(s));
fout.close();
cout<<"\n\nData Successfully Saved to File....\n";
}
void displayData()
{
ifstream fin;
fin.open("Students.txt",ios::in);
while(fin.read((char*)&s,sizeof(s)))
{
s.showData();
}
fin.close();
cout<<"\n\nData Reading from File Successfully Done....\n";
}
void searchData()
{
int n, flag=0;
ifstream fin;
fin.open("Students.txt",ios::in);
cout<<"Enter ID Number you want to search for : ";
cin>>n;
while(fin.read((char*)&s,sizeof(s)))
{
if(n==s.getID())
{
cout<<"The Details of ID No. "<<n<<" are: \n";
s.showData();
flag++;
}
}
fin.close();
if(flag==0)
cout<<"The ID No. "<<n<<" not found....\n\n";
cout<<"\n\nData Reading from File Successfully Done....\n";
}
void deleteData()
{
int n, flag=0;
ifstream fin;
ofstream fout,tout;
fin.open("Students.txt",ios::in);
fout.open("TempStud.txt",ios::out|ios::app);
tout.open("TrashStud.txt",ios::out|ios::app);
cout<<"Enter ID Number you want to delete : ";
cin>>n;
while(fin.read((char*)&s,sizeof(s)))
{
if(n==s.getID())
{
cout<<"The Following ID No. "<< n <<" has been deleted:\n";
s.showData();
tout.write((char*)&s,sizeof(s));
flag++;
}
else
{
fout.write((char*)&s,sizeof(s));
}
}
fout.close();
tout.close();
fin.close();
if(flag==0)
cout<<"The ID No. "<< n <<" not found....\n\n";
remove("Students.dat");
rename("tempStud.txt","Students.txt");
}
void modifyData()
{
int n, flag=0, pos;
fstream fio;
fio.open("Students.txt", ios::in|ios::out);
cout<<"Enter ID Number you want to Modify : ";
cin>>n;
while(fio.read((char*)&s,sizeof(s)))
{
pos=fio.tellg();
if(n==s.getID())
{
cout<<"The Following ID No. "<<n<<" will be modified with new data:\n";
s.showData();
cout<<"\n\nNow Enter the New Details....\n";
s.getData();
fio.seekg(pos-sizeof(s));
fio.write((char*)&s,sizeof(s));
flag++;
}
}
fio.close();
if(flag==0)
cout<<"The ID No. "<<n<<" not found....\n\n";
}
void project()
{
int ch;
do
{
system("cls");
cout<<"...............STUDENT MANAGEMENT SYSTEM..............\n";
cout<<"======================================================\n";
cout<<"0. Exit from Program\n";
cout<<"1. Write Data to File\n";
cout<<"2. Read Data From File\n";
cout<<"3. Search Data From File\n";
cout<<"4. Delete Data From File\n";
cout<<"5. Modify Data in File\n";
cout<<"Enter your choice : ";
cin>>ch;
system("cls");
switch(ch)
{
case 1: addData(); break;
case 2: displayData(); break;
case 3: searchData(); break;
case 4: deleteData(); break;
case 5: modifyData(); break;
}
system("pause");
}while(ch);
}
int main()
{
project();
}
Console Display with problem

Answer 1

Your Student class can only hold 1 set of course information. Your getData() loop is overwriting the same variables over and over, that is why you only see the last course entered. You need to allocate an array (or better, use a std::vector) to hold multiple courses per Student.
There are other problems with your code as well.
Try something more like this instead:
//Project on Student Management
#include <iostream>
#include <fstream>
using namespace std;
struct Course
{
char courseName[100];
char grade[50];
char status[100];
};
class Student
{
int id;
int year;
float cgpa;
int NumberOfcourses;
Course *courses;
char academic_advisor[100];
public:
Student();
~Student();
void getData();
void showData() const;
int getID() const { return id; }
friend ostream& operator<<(ostream &out, const Student &s);
friend istream& operator>>(istream &in, Student &s);
};
ostream& operator<<(ostream &out, const Course &c)
{
out.write(c.courseName, sizeof(c.courseName));
out.write(c.grade, sizeof(c.grade));
out.write(c.status, sizeof(c.status));
return out;
}
istream& operator>>(istream &in, Course &c)
{
in.read(c.courseName, sizeof(c.courseName));
in.read(c.grade, sizeof(c.grade));
in.read(c.status, sizeof(c.status));
return in;
}
ostream& operator<<(ostream &out, const Student &s)
{
out.write((char*)&s.id, sizeof(s.id));
out.write((char*)&s.year, sizeof(s.year));
out.write((char*)&s.cgpa, sizeof(s.cgpa));
out.write(s.academic_advisor, sizeof(s.academic_advisor));
out.write((char*)&s.NumberOfcourses, sizeof(s.NumberOfcourses));
for(int i = 0; i < s.NumberOfcourses; ++i)
{
out << s.courses[i];
}
return out;
}
istream& operator>>(istream &in, Student &s)
{
delete[] s.courses;
s.courses = NULL;
s.NumberOfcourses = 0;
in.read((char*)&s.id, sizeof(s.id));
in.read((char*)&s.year, sizeof(s.year));
in.read((char*)&s.cgpa, sizeof(s.cgpa));
in.read(s.academic_advisor, sizeof(s.academic_advisor));
int NumberOfcourses;
if (in.read((char*)&NumberOfcourses, sizeof(NumberOfcourses)))
{
s.courses = new Course[NumberOfcourses];
for(int i = 0; i < NumberOfcourses; ++i)
{
if (in >> s.courses[i])
s.NumberOfcourses++;
else
break;
}
}
return in;
}
Student::Student()
{
id = 0;
year = 0;
cgpa = 0.0f;
NumberOfcourses = 0;
courses = NULL;
academic_advisor[0] = '\0';
}
Student::~Student()
{
delete[] courses;
}
void Student::getData()
{
cout << "\n\nEnter Student Details......\n";
cout << "Enter ID No. : "; cin >> id;
cout << "Enter Intake Year of the Student: "; cin >> year;
cout << "Enter number of Taken courses: ";
cin >> NumberOfcourses;
cin.ignore();
delete[] courses;
courses = new Course[NumberOfcourses];
for(int a = 0; a < NumberOfcourses; ++a)
{
cout << "\nEnter Subject Name: ";
cin.getline(courses[a].courseName, 100);
cout << "Enter Grade of Subject: ";
cin.getline(courses[a].grade, 50);
cout << "\nEnter Subject Status: ";
cin.getline(courses[a].status, 100);
}
cout << "Enter student CGPA: ";
cin >> cgpa;
cin.ignore();
cout << endl;
cout << "Enter Name of Academic Advisor of Student: ";
cin.getline(academic_advisor, 100);
}
void Student::showData() const
{
cout << "\n\n.......Student Details......\n";
cout << "ID No. : " << id << endl;
cout << "Intake Year : " << year << endl;
cout << "Subjects Taken in Previous Semester : " << endl;
for(int t = 0; t < NumberOfcourses; ++t)
{
cout << "\t" << courses[t].courseName << ": " << courses[t].grade << " (" << courses[t].status << ") ";
cout << endl;
}
cout << "CGPA : " << cgpa << endl;
cout << "Name of academic advisor of Student : " << academic_advisor << endl;
cout << endl;
}
void addData()
{
Student s;
s.getData();
ofstream fout("Students.txt", ios::binary|ios::app);
if (fout << s)
cout << "\n\nData Successfully Saved to File....\n";
else
cerr << "\n\nError Saving Data to File!\n";
}
void displayData()
{
ifstream fin("Students.txt", ios::binary);
Student s;
while (fin >> s)
{
s.showData();
}
if (!fin)
cerr << "\n\nError Reading Data from File!\n";
else
cout << "\n\nData Reading from File Successfully Done....\n";
}
void searchData()
{
int n;
cout << "Enter ID Number you want to search for : ";
cin >> n;
ifstream fin("Students.txt", ios::binary);
Student s;
bool flag = false;
while (fin >> s)
{
if (n == s.getID())
{
cout << "The Details of ID No. " << n << " are: \n";
s.showData();
flag = true;
break;
}
}
if (!fin)
{
cerr << "\n\nError Reading Data from File!\n";
}
else
{
if (!flag)
cout << "The ID No. " << n << " not found....\n\n";
cout << "\n\nData Reading from File Successfully Done....\n";
}
}
void deleteData()
{
int n;
cout << "Enter ID Number you want to delete : ";
cin >> n;
ifstream fin("Students.txt", ios::binary);
ofstream fout("TempStud.txt", ios::binary);
ofstream tout("TrashStud.txt", ios::binary|ios::app);
Student s;
bool flag = false;
while (fin >> s)
{
if (n == s.getID())
{
cout << "The Following ID No. " << n << " will be deleted:\n";
s.showData();
tout << s;
flag = true;
}
else
{
fout << s;
}
}
if (!fin)
{
cerr << "\n\nError Reading Data from File!\n";
}
else if (!fout)
{
cerr << "\n\nError Saving Data to File!\n";
}
else
{
fin.close();
fout.close();
if (!flag)
{
cout << "The ID No. " << n << " not found....\n\n";
remove("tempStud.txt");
}
else
{
remove("Students.txt");
rename("tempStud.txt", "Students.txt");
cout << "\n\nData Successfully Deleted from File....\n";
}
}
}
void modifyData()
{
int n;
cout << "Enter ID Number you want to Modify : ";
cin >> n;
ifstream fin("Students.txt", ios::binary);
ofstream fout("TempStud.txt", ios::binary);
Student s;
bool flag = false;
while (fin >> s)
{
if (n == s.getID())
{
cout << "The Following ID No. " << n << " will be modified with new data:\n";
s.showData();
cout << "\n\nNow Enter the New Details....\n";
s.getData();
flag = true;
}
fout << s;
}
if (!fin)
{
cerr << "\n\nError Reading Data from File!\n";
}
else if (!fout)
{
cerr << "\n\nError Saving Data to File!\n";
}
else
{
fin.close();
fout.close();
if (!flag)
{
cout << "The ID No. " << n << " not found....\n\n";
remove("TempStud.txt");
}
else
{
remove("Students.txt");
rename("TempStud.txt", "Students.txt");
cout << "\n\nData Successfully Updated in File....\n";
}
}
}
void project()
{
int ch;
do
{
system("cls");
cout << "...............STUDENT MANAGEMENT SYSTEM..............\n";
cout << "======================================================\n";
cout << "0. Exit from Program\n";
cout << "1. Write Data to File\n";
cout << "2. Read Data From File\n";
cout << "3. Search Data From File\n";
cout << "4. Delete Data From File\n";
cout << "5. Modify Data in File\n";
cout << "Enter your choice : ";
cin >> ch;
system("cls");
switch (ch)
{
case 1: addData(); break;
case 2: displayData(); break;
case 3: searchData(); break;
case 4: deleteData(); break;
case 5: modifyData(); break;
}
system("pause");
}
while (ch != 0);
}
int main()
{
project();
}
Alternatively:
//Project on Student Management
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
using namespace std;
struct Course
{
string courseName;
string grade;
string status;
};
class Student
{
int id;
int year;
float cgpa;
vector<Course> courses;
string academic_advisor;
public:
Student();
void getData();
void showData() const;
int getID() const { return id; }
friend ostream& operator<<(ostream &out, const Student &s);
friend istream& operator>>(istream &in, Student &s);
};
void writeStr(ostream &out, const string &str)
{
size_t size = str.size();
out.write((char*)&size, sizeof(size));
if (size)
out.write(str.c_str(), size);
}
void readStr(istream &in, string &str)
{
str.clear();
size_t size;
if (in.read((char*)&size, sizeof(size)))
{
if (size > 0)
{
str.resize(size);
in.read(&str[0], size);
}
}
}
ostream& operator<<(ostream &out, const Course &c)
{
writeStr(out, c.courseName);
writeStr(out, c.grade);
writeStr(out, c.status);
return out;
}
istream& operator>>(istream &in, Course &c)
{
readStr(in, c.courseName);
readStr(in, c.grade);
readStr(in, c.status);
return in;
}
ostream& operator<<(ostream &out, const Student &s)
{
out.write((char*)&s.id, sizeof(s.id));
out.write((char*)&s.year, sizeof(s.year));
out.write((char*)&s.cgpa, sizeof(s.cgpa));
writeStr(out, s.academic_advisor);
size_t NumberOfcourses = s.courses.size();
out.write((char*)&NumberOfcourses, sizeof(NumberOfcourses));
for(int i = 0; i < NumberOfcourses; ++i)
{
if (!(out << s.courses[i]))
break;
}
return out;
}
istream& operator>>(istream &in, Student &s)
{
s.courses.clear();
in.read((char*)&s.id, sizeof(s.id));
in.read((char*)&s.year, sizeof(s.year));
in.read((char*)&s.cgpa, sizeof(s.cgpa));
readStr(in, s.academic_advisor);
size_t NumberOfcourses;
if (in.read((char*)&NumberOfcourses, sizeof(NumberOfcourses)))
{
s.courses.reserve(NumberOfcourses);
Course c;
for(size_t i = 0; i < NumberOfcourses; ++i)
{
if (in >> c)
s.courses.push_back(c);
else
break;
}
}
return in;
}
Student::Student()
{
id = 0;
year = 0;
cgpa = 0.0f;
}
void Student::getData()
{
courses.clear();
cout << "\n\nEnter Student Details......\n";
cout << "Enter ID No. : "; cin >> id;
cout << "Enter Intake Year of the Student: "; cin >> year;
cout << "Enter number of Taken courses: ";
size_t NumberOfcourses;
cin >> NumberOfcourses;
cin.ignore();
courses.reserve(NumberOfcourses);
Course c;
for(int a = 0; a < NumberOfcourses; ++a)
{
cout << "\nEnter Subject Name: ";
getline(cin, c.courseName);
cout << "Enter Grade of Subject: ";
getline(cin, c.grade);
cout << "\nEnter Subject Status: ";
getline(cin, c.status);
s.courses.push_back(c);
}
cout << "Enter student CGPA: ";
cin >> cgpa;
cin.ignore();
cout << endl;
cout << "Enter Name of Academic Advisor of Student: ";
getline(cin, academic_advisor);
}
void Student::showData() const
{
cout << "\n\n.......Student Details......\n";
cout << "ID No. : " << id << endl;
cout << "Intake Year : " << year << endl;
cout << "Subjects Taken in Previous Semester : " << endl;
for(size_t t = 0; t < courses.size(); ++t)
{
cout << "\t" << courses[t].courseName << ": " << courses[t].grade << " (" << courses[t].status << ") ";
cout << endl;
}
cout << "CGPA : " << cgpa << endl;
cout << "Name of academic advisor of Student : " << academic_advisor << endl;
cout << endl;
}
void addData()
{
Student s;
s.getData();
ofstream fout("Students.txt", ios::binary|ios::app);
if (fout << s)
cout << "\n\nData Successfully Saved to File....\n";
else
cerr << "\n\nError Saving Data to File!\n";
}
void displayData()
{
ifstream fin("Students.txt", ios::binary);
Student s;
while (fin >> s)
{
s.showData();
}
if (!fin)
cerr << "\n\nError Reading Data from File!\n";
else
cout << "\n\nData Reading from File Successfully Done....\n";
}
void searchData()
{
int n;
cout << "Enter ID Number you want to search for : ";
cin >> n;
ifstream fin("Students.txt", ios::binary);
Student s;
bool flag = false;
while (fin >> s)
{
if (n == s.getID())
{
cout << "The Details of ID No. " << n << " are: \n";
s.showData();
flag = true;
break;
}
}
if (!fin)
{
cerr << "\n\nError Reading Data from File!\n";
}
else
{
if (!flag)
cout << "The ID No. " << n << " not found....\n\n";
cout << "\n\nData Reading from File Successfully Done....\n";
}
}
void deleteData()
{
int n;
cout << "Enter ID Number you want to delete : ";
cin >> n;
ifstream fin("Students.txt", ios::binary);
ofstream fout("TempStud.txt", ios::binary);
ofstream tout("TrashStud.txt", ios::binary|ios::app);
Student s;
bool flag = false;
while (fin >> s)
{
if (n == s.getID())
{
cout << "The Following ID No. " << n << " will be deleted:\n";
s.showData();
tout << s;
flag = true;
}
else
{
fout << s;
}
}
if (!fin)
{
cerr << "\n\nError Reading Data from File!\n";
}
else if (!fout)
{
cerr << "\n\nError Saving Data to File!\n";
}
else
{
fin.close();
fout.close();
if (!flag)
{
cout << "The ID No. " << n << " not found....\n\n";
remove("tempStud.txt");
}
else
{
remove("Students.txt");
rename("tempStud.txt", "Students.txt");
cout << "\n\nData Successfully Deleted from File....\n";
}
}
}
void modifyData()
{
int n;
cout << "Enter ID Number you want to Modify : ";
cin >> n;
ifstream fin("Students.txt", ios::binary);
ofstream fout("TempStud.txt", ios::binary);
Student s;
bool flag = false;
while (fin >> s)
{
if (n == s.getID())
{
cout << "The Following ID No. " << n << " will be modified with new data:\n";
s.showData();
cout << "\n\nNow Enter the New Details....\n";
s.getData();
flag = true;
}
fout << s;
}
if (!fin)
{
cerr << "\n\nError Reading Data from File!\n";
}
else if (!fout)
{
cerr << "\n\nError Saving Data to File!\n";
}
else
{
fin.close();
fout.close();
if (!flag)
{
cout << "The ID No. " << n << " not found....\n\n";
remove("TempStud.txt");
}
else
{
remove("Students.txt");
rename("TempStud.txt", "Students.txt");
cout << "\n\nData Successfully Updated in File....\n";
}
}
}
void project()
{
int ch;
do
{
system("cls");
cout << "...............STUDENT MANAGEMENT SYSTEM..............\n";
cout << "======================================================\n";
cout << "0. Exit from Program\n";
cout << "1. Write Data to File\n";
cout << "2. Read Data From File\n";
cout << "3. Search Data From File\n";
cout << "4. Delete Data From File\n";
cout << "5. Modify Data in File\n";
cout << "Enter your choice : ";
cin >> ch;
system("cls");
switch (ch)
{
case 1: addData(); break;
case 2: displayData(); break;
case 3: searchData(); break;
case 4: deleteData(); break;
case 5: modifyData(); break;
}
system("pause");
}
while (ch != 0);
}
int main()
{
project();
}