// C++ program to modify the content
// of a binary file
#include <bits/stdc++.h>
using namespace std;
class abc {
int roll;
char name[20];
public:
void getdata(int, char[]);
void update(int, int, char[]);
void testcase1();
void testcase2();
void putdata();
};
// Code to display the data of the
// data of the object
void abc::putdata()
{
cout << "roll no: ";
cout << roll;
cout << "\nname: ";
cout << name;
}
// Code to set the value to the object
void abc::getdata(int a, char str[])
{
// setting the new roll no
roll = a;
// setting new name
strcpy(name, str);
}
void abc::update(int rno, int r, char str[])
{
// code to update and modify
// the content of the binary file
int pos, flag = 0;
// rno=9
fstream fs;
fs.open("he.dat",
ios::in | ios::binary | ios::out);
while (!fs.eof()) {
// storing the position of
// current file pointeri.e. at
// the end of previously read record
pos = fs.tellg();
fs.read((char*)this, sizeof(abc));
if (fs) {
// comparing the roll no with that
// of the entered roll number
if (rno == roll) {
flag = 1;
// setting the new (modified )
// data of the object or new record
getdata(r, str);
// placing the put(writing) pointer
// at the starting of the record
fs.seekp(pos);
// writing the object to the file
fs.write((char*)this, sizeof(abc));
// display the data
putdata();
break;
}
}
}
fs.close();
if (flag == 1)
cout << "\nrecord successfully modified \n";
else
cout << "\nrecord not found \n";
}
// Sample input 1
void abc::testcase1()
{
int rno, r;
char name[20];
// roll no to be searched
rno = 1;
// new roll no
r = 11;
// new name
strcpy(name, "Geek");
// call update function with new values
update(rno, r, name);
}
// Sample input 2
void abc::testcase2()
{
int rno, r;
char name[20];
// roll no to be searched
rno = 4;
// new roll no
r = 14;
// new name
strcpy(name, "Geek2");
// call update function with the new values
update(rno, r, name);
}
// Driver code
int main()
{
abc s;
// sample case 1
s.testcase1();
// sample case 2
s.testcase2();
return 0;
}
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