The Mesopotamian economy was based on bartering—that is, trading goods and services for other goods and services. Bartering was necessary for people in Mesopotamia to get the resources they lacked. As a result, ancient Mesopotamians would trade with people from other areas. The Mesopotamians also used currency to help facilitate trade. Unlike modern systems of currency, which use paper money or coins, their system used barley. To procure this barley, people had to borrow from a banker who kept barley. Mesopotamians also used metals such as lead, copper, bronze, tin, gold, and silver, for currency. The writing system that developed in Mesopotamian (first in the form of pictograms and later as cuneiform) facilitated bartering, as scribes could keep contracts and records of trades. Once a deal was completed, it was recorded on a cylinder.