In the city, business is prosperous and transportation is developed. Many cities have set up shops to serve businessmen, and there have been original bills of exchange "flying money" or "convenient exchange" and credit institutions "counters". At that time, the exchange of goods was active, and the currency balance was frequent. New achievements have been made in smelting technology in the Tang Dynasty. There are 65,438+068 silver, copper, iron and tin smelters in China. Metal objects are mainly hammered and cast, and cutting, chiseling and welding techniques are used.