~cpp #include<iostream> #include<fstream> using namespace std; void main() { char fileName[10]; cout << " : "; cin >> fileName; ifstream fin(fileName); ofstream fout("output.txt"); char temp; while(fin.get(temp)) { temp += 3; // +3 fout << temp; cout << temp; } fin.close(); fout.close(); cout << "\n : "; cin >> fileName; ifstream fin1("output.txt"); ofstream fout1(fileName); while(fin1.get(temp)) { temp -= 3; // -3 fout1 << temp; cout << temp; } fin1.close(); fout1.close(); }