C++ examples for File Stream:stream
Save person objects do disk I/O
#include <fstream> #include <iostream> using namespace std; class person/*from w w w . ja v a 2s . c o m*/ { protected: char name[40]; int age; public: void getData(void) //get person's data { cout << "\n Enter last name: "; cin >> name; cout << " Enter age: "; cin >> age; } void showData(void) //display person's data { cout << "\n Name: " << name; cout << "\n Age: " << age; } void diskIn(int); //read from file void diskOut(); //write to file static int diskCount(); //return number of persons in file }; void person::diskIn(int pn) //read person number pn from file { ifstream infile; //make stream infile.open("PERSFILE.DAT", ios::binary); //open it infile.seekg( pn*sizeof(person) ); //move file ptr infile.read( (char*)this, sizeof(*this) ); //read one person } void person::diskOut() //write person to end of file { ofstream outfile; //make stream, open it outfile.open("PERSFILE.DAT", ios::app | ios::binary); outfile.write( (char*)this, sizeof(*this) ); //write to it } int person::diskCount() //return number of persons { //in file ifstream infile; infile.open("PERSFILE.DAT", ios::binary); infile.seekg(0, ios::end); //go to 0 bytes from end //calculate number of persons return (int)infile.tellg() / sizeof(person); } int main() { person p; char ch; do { cout << "Enter data for person:"; p.getData(); //get data p.diskOut(); //write to disk cout << "Do another (y/n)? "; cin >> ch; } while(ch=='y'); //until user enters 'n' int n = person::diskCount(); //how many persons in file? cout << "There are " << n << " persons in file\n"; for(int j=0; j<n; j++) //for each one, { cout << "\nPerson " << j; p.diskIn(j); //read person from disk p.showData(); } cout << endl; return 0; }