Program to show various operations i.e. read, write and modify in a text file.

Operations on a text file :

#include<stdio.h>

#include<fstream.h>

#include<stdlib.h>

#include<conio.h>

class stud

{
   int rno,obj;

   char name[25];

   public:

        void getdata()

       {cout<<"enter rno and name::";

        cin>>rno>>name;}

        void showdata()

       {

        cout<<"\nrno is:"<<rno;

        cout<<"\nname is:"<<name;

       }
};

void main()

{

    int obj;

    char name[25];

    stud stu[5];

    clrscr();

    fstream fl1;

    fl1.open("dfile",ios::out|ios::in|ios::binary|ios::ate);

    cout<<"\n <----Writing in the file---->"<<endl;

    for(int i=0;i<=4;i++)

    {

    stu[i].getdata();

    fl1.write((char*)&stu[i],sizeof(stu[i]));

    }

    fl1.seekg(0);

    cout<<"\n <----Reading from the file---->"<<endl;

    for(i=0;i<=4;i++)

    {

    fl1.read((char*)&stu[i],sizeof(stu[i]));

    stu[i].showdata();

    }

    cout<<"\n<--Modification in the file-->"<<endl;

    cout<<"\nEnter the obj to update";

    cin>>obj;

    int loc=(obj-1)*sizeof(stu);

    if(fl1.eof())

    fl1.clear();

    fl1.seekp(loc);

    stud smo;

    cout<<"\nenter new value of obj";

    smo.getdata();

    fl1.write((char*)&smo,sizeof(smo));

    fl1.seekg(0);

    cout<<"\n<----Contents of file after modification---->"<<endl;

    for(i=0;i<=4;i++)

    {

    fl1.read((char*)&stu[i],sizeof(stu[i]));

    stu[i].showdata();

    }

    getch();

    }