While it is possible to pay with a card and withdraw cash just about everywhere in large cities and in many highly developed countries, it may be almost impossible in other regions. That means you should find out what the situation is in the country you're visiting before your trip.
Imagine you've just arrived at your dream destination, and you want to get a snack and then take a taxi to your hotel. Then you see the sign: cash only. This is hardly unusual because taxis, public transport, and small food or drink stands rarely accept card payments.
Experienced travelers always carry little local cash with them. The rule of thumb here is: as much as necessary, as little as possible. If you travel off the beaten path, you should have an emergency reserve of US dollars or euros in addition to the local currency. This will help bridge the gap in emergency situations when you can't withdraw money from an ATM.
Change a small amount (up to CHF 200) of money into the local currency before you depart or at the airport. If you need major currencies such as euros, dollars, pounds, or yen, it is best to exchange an amount at your bank while you're still in Switzerland. Exotic currencies, such as baht or krona, are usually cheaper in the destination country. Official banks and hotels are reputable options for exchanging money abroad.
If you need the local currency quickly while you're traveling, you can withdraw cash from an ATM. However, cash withdrawals abroad are subject to a fee that varies depending on the provider. The operator of the ATM may charge a fee as well.