Here is part of a program that reads keyboard input into a vector of string objects, stores the string contents (not the objects) in a file, and then copies the file contents back into a vector of string objects:
int main()
{
using namespace std;
vector vostr;
string temp;
// acquire strings
cout << "Enter strings (empty line to quit):\n";
while (getline(cin,temp) && temp[0] != '\0')
vostr.push_back(temp);
cout << "Here is your input.\n";
for_each(vostr.begin(), vostr.end(), ShowStr);
// store in a file
ofstream fout("strings.dat", ios_base::out | ios_base::binary);
for_each(vostr.begin(), vostr.end(), Store(fout));
fout.close();
// recover file contents
vector vistr;
ifstream fin("strings.dat", ios_base::in | ios_base::binary);
if (!fin.is_open())
{
cerr << "Could not open file for input.\n";

• exit(EXIT_FAILURE);
  }
  GetStrs(fin, vistr);
  cout << "\nHere are the strings read from the file:\n";
  for_each(vistr.begin(), vistr.end(), ShowStr);
  return 0;
  }
  Note that the file is opened in binary format and that the intention is that I/O be accomplished with read() and write(). Quite a bit remains to be done:
  Write a void ShowStr(const string &) function that displays a string object followed by a newline character.
  Write a Store functor that writes string information to a file.The Store constructor should specify an ifstream object, and the overloaded operator()(const string &) should indicate the string to write.A workable plan is to first write the string’s size to the file and then write the string contents. For example, if len holds the string size, you could use this:
  os.write((char *)&len, sizeof(std::size_t)); // store length os.write(s.data(), len); // store characters The data() member returns a pointer to an array that holds the characters in
  the string. It’s similar to the c_str() member except that the latter appends a null character.
  Write a GetStrs() function that recovers information from the file. It can use read() to obtain the size of a string and then use a loop to read that many characters from the file, appending them to an initially empty temporary string. Because a string’s data is private, you have to use a class method to get data into the string rather than read directly into it.