1.1.13.7 file

• When you studied cin and cout very well, you will find that file operation is so easy. just change cin or cout to your ifstream , ofstream or fstream object.
  std::fstream fs; 
  fs.open ("test.txt", ios_base::in| ios_base::binary); 
  if(!ifs.is_open()) 
       exit(1); 
  char c = ifs.get(); 
  // use all previous input methods 
  ifs.close();
• Only read ifsteam; Only write ofsteam; write and read fstream.
• For ios_base::binary mode, use write() and read() funciton.
• For writing, pay attention to the difference between ios_base::trunc and ios_base::app
• Random access is used mostly on binary file. Because the position can be pinpointed exactly. For seekg() for input, and seekp() for output.(p is put, g is get) It move the pointer. tellp() and tellg() function. It tell the position of pointer.