Many commodities have served as universal equivalents in history, including early livestock, fabrics and shells. Later, precious metals such as gold and silver were gradually separated from commodities and acted as universal equivalents because of their small size, high value, easy separation, easy wear and tear, easy storage and carrying. Metal money was originally circulated in the form of gold and silver bars. It is inconvenient to check the weight and color of each transaction, so coins with certain shape, weight, color and denomination value appear. Metal coins will gradually wear out in the long-term circulation process and become a currency with insufficient value, which will generally not affect its use as a coin with full value. Later, as a symbol of value, paper money came into being. Compared with metal currency, paper money is cheaper to make, easier to keep, carry and transport, and avoids the wear and tear of coins in circulation. With the rapid development of information technology, especially the realization of computer networking in banks, "electronic money" with computers for storage, transfer, purchase and payment has emerged, and people increasingly rely on the computer system of banks to complete the automatic transfer business.