#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 (;;)
{
...
}

while(1) {
...
}