switch only uses builtin types.Looks like Yarin gets the last laugh.Code:#include <iostream> int main() { using namespace std; double num1, meters, feet, kilos, pounds, liters, gallons, kms, miles; string option; cout << "English/Metric Conversion Calculator v1.0" << endl; cout << "-----------------------------------------" << endl; cout << "1. Convert feet to meters" << endl; cout << "2. Convert meters to feet" << endl; cout << "3. Convert lbs. to kilograms" << endl; cout << "4. Convert kilograms to lbs." << endl; cout << "5. Convert gallons to liters" << endl; cout << "6. Convert liters to gallons" << endl; cout << "7. Convert square miles to square kilometers" << endl; cout << "8. Convert square kilometers to square miles" << endl; cout << "9. Quit" << endl << endl; do // makes sure the loop is ran at least once { cout << endl << "Please select the conversion type you want to perform:" << endl; getline(cin, option); if(option == "1") { cout << endl << "Enter the number of feet to convert to meters: "; cin >> num1; meters = num1 * 0.3048; cout << endl << num1 << " feet is equal to " << meters << " meters." << endl; } else if(option == "2") { cout << endl << "Enter the number of meters to convert to feet: "; cin >> num1; feet = num1 * 3.2808399; cout << endl << num1 << " meters is equal to " << feet << " feet." << endl; } else if(option == "3") { cout << endl << "Enter the number of pounds to convert to kilograms: "; cin >> num1; kilos = num1 * 0.45359237; cout << endl << num1 << " lbs. is equal to " << kilos << " kilograms." << endl; } else if(option == "4") { cout << endl << "Enter the number of kilograms to convert to pounds: "; cin >> num1; pounds = num1 * 2.20462262; cout << endl << num1 << " kilograms is equal to " << pounds << " lbs." << endl; } else if(option == "5") { cout << endl << "Enter the number of gallons to convert to liters: "; cin >> num1; liters = num1 * 3.7854118; cout << endl << num1 << " gallons is equal to " << liters << " liters." << endl; } else if(option == "6") { cout << endl << "Enter the number of liters to convert to gallons: "; cin >> num1; gallons = num1 * 0.264172051; cout << endl << num1 << " liters is equal to " << gallons << " gallons." << endl; } else if(option == "7") { cout << endl << "Enter the number of square miles to convert into square kilometers: "; cin >> num1; kms = num1 * 2.58998811; cout << endl << num1 << " square miles is equal to " << kms << " square kilometers." << endl; } else if(option == "8") { cout << endl << "Enter the number of square kilometers to convert into square miles: "; cin >> num1; miles = num1 * 0.386102159; cout << endl << num1 << " square kilometers is equal to " << miles << " square miles." << endl; } else { cout << "That is an invalid option. Please choose again." << endl; } } while(option != "9"); // keep looping to ask user as long as '9' isn't chosen cout << "Thank you for using Conversion Calculator v1.0!" << endl; return 0; }