The franc is the currency and legal tender of Switzerland and Liechtenstein.
Most all restaurants and public places take credit cards/debit cards. The ones that don’t will have it marked on the door “Pas de cartes de credit” in French and “Keine kreditkarten” in German. There are plenty of ATM machines at the Geneva and Zurich airports, as well as full service banks where you could change USD to CHF.
Traveler’s checks can be exchanged at banks or exchange offices. Some stores in tourist areas will also accept them for payment. For best rates, travelers should take the checks in euros, US dollars or British pounds.
Finally, be careful of your money, wallet and credit cards when you are in crowded areas like markets, busses, metro stations, subway cars and train stations. Your pocket could be picked at these places if you’re not vigilant.