Accounting systems record financial transactions. The two major accounting systems are cash accounting and accrual accounting. Cash accounting systems recognize transactions and events when cash is received or paid; they do not recognize non-cash events. Accrual accounting systems, on the other hand, record payments and receipts when parties enter into a commitment, not when cash changes hands. For instance, an accrual accounting system would record the purchase of naval helicopters when the government signs a contract to buy the helicopters, not when the helicopters are actually delivered and paid for (which would be the case in a cash accounting system). An accrual accounting system views the commitment, rather than the exchange of cash for goods or services, as the event that has economic significance. Most governments rely on cash accounting systems.