Reading and Writing Binary data through fstream

C++ file input and output are typically achieved by using an object of one of the following classes:

• ifstream for reading input only.

• ofstream for writing output only.

• fstream for reading and writing from/to one file.

All three classes are defined in <fstream.h>. Throughout this page, the term "file stream" will be used when referring to features that apply equally to all three classes.

include<iostream.h>
#include<conio.h>
#include<fstream.h>
#include<stdio.h>
char choice,name[10];
int r;
class student
{
	int rno;
	char name[30];
	float marks;
public:
void take()
{
	cout<<"\nEnter roll no. :";
	cin>>rno;
	cout<<"\nEnter name :";
	gets(name);
	cout<<"\nEnter marks :";
	cin>>marks;
}
void put()
{
	cout<<"\nRoll no.:"<<rno;
	cout<<"\nName is:"<<name;
	cout<<"\nMarks is:"<<marks;
}
int rnr(){
	return rno;
}
}obj;
void reading()
{
	cout<<"Enter name of file ";
	gets(name);
	ofstream fout;
	fout.open(name,ios::out,ios::binary);
do
{
	obj.take();
	fout.write((char*)&obj,sizeof(obj));
	cout<<"Want to enter more?(y/n):";
	cin>>choice;
}while(choice=='y');
	fout.close();
}
void opening()
{
	cout<<"Enter name of file ";
	gets(name);
	ifstream fin;
	fin.open(name,ios::in,ios::binary);
while(fin.read((char*)&obj,sizeof(obj)))
{
	obj.put();
}
	fin.close();
}
void search()
{
	cout<<"Enter name of file ";
	cin>>name;
	ifstream fin;
	fin.open(name,ios::in,ios::binary);
	cout<<"\nEnter roll no. to be searched :";
	cin>>r;
	fin.seekg(0);
while(fin.read((char*)&obj,sizeof(obj)))
{
	if(obj.rnr()==r)
{
	obj.put();
	break;
}
}
	fin.close();
}
void modify()
{
	cout<<"\nEnter name of file :";
	gets(name);
	ifstream fin;
	fin.open(name,ios::in||ios::binary);
	ofstream fout;
	fout.open(name,ios::out||ios::binary);
	cout<<"\nEnter roll no. to be modified :";
	cin>>r;
while(fin.read((char*)&obj,sizeof(obj)))
{	
	int pos=fin.tellg();
if(obj.rnr()==r)
{
	obj.take();
	fout.seekp(pos-sizeof(obj));
	fout.write((char*)&obj,sizeof(obj));
	break;
}
}
	fout.close();
	fin.close();
}
void dell()
{
	cout<<"\nEnter name of file :";
	gets(name);
	ifstream fin;
	fin.open(name,ios::in||ios::binary);
	ofstream fout;
	fout.open("temp.txt",ios::out||ios::binary);
	cout<<"\nEnter roll no. to be deleted:";
	cin>>r;
	fin.seekg(0);
while(fin.read((char*)&obj,sizeof(obj)))
{
	if(obj.rnr()!=r)
	fout.write((char*)&obj,sizeof(obj));
}
	fout.close();
	fin.close();
	remove(name);
	rename("temp.txt",name);
}
void main()
{
	clrscr();
	char ch;
	int o;
do{
	clrscr();
	cout<<"\nTo read:1\nTo open:2\nTo search:3\nTo modify:4\nTo Delete:5  ---";
cin>>o;
switch(o)
{
case 1:reading();
      break;
case 2:opening();
	break;
case 3:search();
	break;
case 4:modify();
	break;
case 5:dell();
       break;
}
	cout<<"\n\nWnat to continue?(y/n):";
	cin>>ch;
}while(ch=='y');
	getch();
}

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