modification

[poorni]

I created this project for students to take a test and included file handling. The program works well but the problem is that when a student takes the test, the rest of the data in the file gets erased. code:

  Put 
#include<iostream.h>
#include<conio.h>
#include<fstream.h>
#include<ctype.h>
#include<string.h>
#include<process.h>
#include<stdlib.h>
#include<stdio.h>
int count=0,i,n=0;
class basic
{
public:
char name[30],fname[30],mname[30],ph[20],address[100];
int cid;
int score;
char dob[15];
basic()
{
score=0;
strcpy(name,"-");
cid=0;
strcpy(dob,"-");
}
};
class info:public basic
{
int ch1,ch2,ch3,ch4,ch5,ch6,ch7,ch8,ch9,ch10;
public:
void acc();
void eco();
void comp();
void input();
void display();
void test();
void scorer();
void scored();
}d,s[100];
void info::acc()
{
cout<<"PART A: ACCOUNTS:";
cout<<"\n1.In the absence of Partnership Deed, partners can claim for";
cout<<"\n1.Salary\n2.Interest on capital";
cout<<"\n3.Interest of loans and advances\n4.Distribution of profit in their capital ratio";
cout<<"\nAns:";
cin>>ch1;
cout<<"\n\n2.If the new partner is unable to bring his/her share of goodwill, then goodwill is adjusted by";
cout<<"\n1.Debiting Goodwill Account and crediting sacrificing Partner's Capital Account\n2.Debiting Goodwill Account and crediting all Partner's Capital Account in new ratio";
cout<<"\n3.Debiting sacrificing Partners Capital Account and crediting gaining Partners Capital Account\n4.Debiting gaining Partner's Capital Account and crediting sacrificing Partner's Capital Account";
cout<<"\nAns:";
cin>>ch2;
cout<<"\n\n3.Which of the following items is recorded on the debit side of Retiring Partner’s Capital Account?";
cout<<"\n1.Interest on Capital\n2.Interest on Drawings";
cout<<"\n3.Share of General Reserve\n4.Share of credit balance of Profit and Loss Account";
cout<<"\nAns:";
cin>>ch3;
cout<<"\n\n4.Which of the following accounts is credited to transfer profit on revaluation of assets and liabilities, if the Partner’s Capital Accounts is maintained by Fixed Method?";
cout<<"\n1.Revaluation Account\n2.Partner's Capital Account";
cout<<"\n3.Partner's Current Account\n4.Profit and Loss Appropriation Account";
cout<<"\nAns:";
}
void info::eco()
{
cout<<"\n\nPART B:ECONOMICS";
cout<<"\n5.Which of these statements is correct regarding the massive unemployment?";
cout<<"\n1.It is shown by a point inside the PPC.\n2.It leads to the leftward shift of the PPC.";
cout<<"\n3.It leads to the rightward shift of the PPC.\n4.It is represented by a point lying on the PPC.";
cout<<"\nAns:";
cin>>ch5;
cout<<"\n6.Which of the following degrees of price elasticity will be depicted by a vertical demand curve which is parallel to y-axis?";
cout<<"\n1.Elastic  \n2.Perfectly elastic";
cout<<"\n3.Inelastic  \n4.Perfectly inelastic";
cout<<"\nAns:";
cin>>ch6;
cout<<"\n7.Which of the following curves is an inverse S-shaped curve?";
cout<<"\n1.Average Cost \n2.Marginal Cost";
cout<<"\n3.Total Variable Cost\n4.Average Fixed Cost";
cout<<"\nAns:";
cin>>ch7;
cout<<"\n8.Which of the following characteristics is not correct for the demand curve faced by a firm under perfect competition?";
cout<<"\n1.Demand curve is elastic.\n2.Demand curve is downward sloping.";
cout<<"\n3.Demand curve coincides with MR curve.\n4.Demand curve depicts the price of product";
cout<<"\nAns:";
cin>>ch8;
}
void info::comp()
{
cout<<"\n\nPART C: COMPUTERS";
cout<<"\n9.In which visibility mode are data in structures, by default?";
cout<<"\n1.Private\n2.Protected\n3.Public\n4.None of the above";
cout<<"\nAns:";
cin>>ch9;
cout<<"\n10.Name the header file to which the function rand( ) belongs?";
cout<<"\n1.#include<stdlib.h>\n2.#include<iomanip.h>";
cout<<"\n3.#include<stdio.h>\n4.#include<fstream.h>";
cout<<"\nAns:";
cin>>ch10;
}
void info::scorer()
{
ofstream f;
f.open("pripoo.txt",ios::out);
if(ch1==3)
score=score+1;
if(ch2==4)
score+=1;
if(ch3==2)
score+=1;
if(ch4==3)
score+=1;
if(ch5==1)
score+=1;
if(ch6==4)
score+=1;
if(ch7==3)
score+=1;
if(ch8==2)
score+=1;
if(ch9==3)
score+=1;
if(ch10==1)
score+=1;
f<<score;
f.close();
}
void info::scored()
{
ifstream f;
f.open("pripoo.txt",ios::in);
f>>score;
cout<<"\n\tScore:"<<score;
}
void info::input()
{
clrscr();
cout<<"\n\n\t\tEntering a new student!";
ofstream f;
f.open("pripoo.txt",ios::app);
cout<<"\n\n\tEnter details of student!";
cout<<"\n\t-------------------------\n";
cout<<"\n\tEnter Name:";
gets(name);
cout<<"\n\tEnter the student ID:";
cin>>cid;
cout<<"\n\tDate Of Birth as DD/MM/YY:";
gets(dob);
cout<<"\n\tEnter Father's Name:";
gets(fname);
cout<<"\n\tEnter Mother's Name:";
gets(mname);
cout<<"\n\tEnter telephone number with the STD code:";
gets(ph);
cout<<"\n\tEnter address:";
gets(address);
getch();
}
void info::display()
{
cout<<"\n\n\tDisplay students: ";
cout<<"\n\t-------------------\n";
cout<<"\n\n\tStudent details are:";
cout<<"\n\n\tName:";
cout<<name;
cout<<"\n\tID:";
cout<<cid;
cout<<"\n\tDate of birth:";
cout<<dob;
cout<<"\n\tFather's Name:";
cout<<fname;
cout<<"\n\tMother's Name:";
cout<<mname;
cout<<"\n\tScore:";
cout<<score;
cout<<"\n\tPhone Number:";
cout<<ph;
cout<<"\n\tResidence:";
cout<<address;
}
void info::test()
{
acc();
eco();
comp();
scorer();
clrscr();
}
void main()
{
clrscr();
f:
cout<<"\nMain Menu";
cout<<"\n1.Enter student details";
cout<<"\n2.Take the test";
cout<<"\n3.View a single student's report";
cout<<"\n4.View the report of all students";
cout<<"\n5.Exit";
cout<<"\nEnter your choice:";
int ch;
cin>>ch;
switch(ch)
{
case 1:
{
ofstream file1("pripoo.txt",ios::app);
d.input();
file1.write((char*)&d,sizeof(d));
file1.close();
goto f;
}
case 2:
{
cout<<"\nEnter the id of the student taking the test:";
ifstream fout("pripoo.txt",ios::in);
int pos;
int tid;
cin>>tid;
while(!fout.eof())
{
pos=fout.tellg();
fout.read((char*)&d,sizeof(d));
if(d.cid==tid)
{
d.test();
fout.seekg(pos);
break;
}
}
fout.close();
goto f;
}
case 3:
{
cout<<"\nEnter the ID:";
int id;
cin>>id;
ifstream fout;
fout.seekg(0);
fout.open("pripoo.txt",ios::in);
while(!fout.eof())
{
fout.read((char*)&d,sizeof(d));
if(d.cid==id)
{
d.display();
break;
}
}
fout.close();
goto f;
}
case 4:
{
ifstream fin("pripoo.txt",ios::in);
fin.seekg(0);
while(fin.read((char*)&d,sizeof(d)))
{
d.display();
}
fin.close();
goto f;
}
case 5:
{
cout<<"\nPress any key to exit";
getch();
exit(0);
}
}
}
the code you need help with here.

It would be great if someone could help me with this. Thank you very much for taking time and reading this post.