#include <iostream.h>


int choice;
double pounds;
double USdollar;
double Euro;
double interest;

int main(){

     cout << "Select what you want to convert." <<endl;
     cout << "1.Pounds to US dollar." <<endl;
     cout << "2.Pounds to Euro." << endl;
     cin >> choice;

while (true){

//converts pounds to US dollars
     if (choice == 1){
          cout << "Please enter amount you want to convert." <<endl;
          cin >> pounds;
          USdollar = pounds * 0.5; //change the conversion rate
          cout << USdollar<< endl;
          if (pounds <= 1000){
                 cout << "Interest rate is 1% of this amount." <<endl;
                 interest = USdollar + (USdollar * 0.01);
                 cout << interest << endl;
                 }
                 if (pounds > 1000){
                 cout << "Interest rate is 3% of this amount." <<endl;
                 interest = USdollar + (USdollar * 0.03);
                 cout << interest << endl;
                 }break;
          }
//converts pounds to euro
     if (choice == 2){
          cout << "Please enter amount you want to convert." <<endl;
          cin >> pounds;
          Euro = pounds * 0.3; //change the conversion rate
          cout << Euro<< endl;
          if (pounds <= 1000){
                 cout << "Interest rate is 1% of this amount." <<endl;
                 interest = Euro + (Euro * 0.01);
                 cout << interest << endl;
                 }
                 if (pounds > 1000){
                 cout << "Interest rate is 3% of this amount." <<endl;
                 interest = Euro + (Euro * 0.03);
                 cout << interest << endl;
                 }break;
          }
     if (choice != 1 && choice !=2){
          cout <<"Invalid choice. Enter again."<<endl;
        }
     }return 0;
}

bool keepLooping = true;

while (keepLooping)
{
...
}

for (;;)
{
...
}