Adding to a file without erasing what is inside - c++

Question

I am writing a code that takes some input from the user and stores it in a file. My code is supposed to keep the old data and add the new data, but every time I run the code the old data that was in the file gets replaced by the new one.
if(input == 1){
outFile.open("personnel2.dat");
int numRecords = 0;
do{
cout << "#1 of 7 - Enter Employee Worker ID Code(i.e AF123): ";
cin >> id;
cout << "#2 of 7 - Enter Employee LAST Name: ";
cin >> lastN;
cout << "#3 of 7 - Enter Employee FIRST Name: ";
cin >> firstN;
cout << "#4 of 7 - Enter Employee Work Hours: ";
cin >> workH;
cout << "#5 of 7 - Enter Employee Pay Rate: ";
cin >> payRate;
cout << "#6 of 7 - Enter FEDERAL Tax Rate: ";
cin >> federalTax;
cout << "#7 of 7 - Enter STATE Tax Rate: ";
cin >> stateTax;
outFile << id << " " << lastN << " " << firstN << " " << workH << " " << payRate << " "
<< federalTax << " " << stateTax << "\n";
numRecords++;
cout << "Enter ANOTHER Personnel records? (Y/N): ";
cin >> moreRecords;
}while(moreRecords != 'N' && moreRecords != 'n');
outFile.close();
cout << numRecords << " records written to the data file.\n";
}

Answer 1

Change outFile.open("personnel2.dat");
to
outFile.open("personnel2.dat", std::fstream::app);
to set the mode to append, assuming you are using fstream::open().

Answer 2

Assuming that outfile is instance of std::ofstream, The reason behind that is that when you use open() function on ofstream object, the file is opened in ios_base::out mode which enforces removal of previous content before inserting new one.
In order to append the data, you have to explicitly specify the append mode.
Example:
#include <fstream> // std::ofstream
int main () {
std::ofstream ofs;
ofs.open ("test.txt", std::ofstream::out | std::ofstream::app);
ofs << " more lorem ipsum";
ofs.close();
return 0;
}
Source: http://www.cplusplus.com/reference/fstream/ofstream/open/
In your case, you have to change it in this way:
outFile.open("personnel2.dat", std::ofstream::out | std::ofstream::app);