The Ethereum platform uses "gas", a unit of account in the Ethereum virtual machine used to calculate the transaction fee. It represents the amount of ether that the sender of the transaction must pay to the network in order for the transaction to be included in the blockchain. Each type of operation that an Ethereum virtual machine can perform is hard-coded with a certain gas cost, which should be approximately proportional to the monetary value of the resources (for example, computing and storage) that the node must expend or allocate to perform this operation. This fee mechanism is designed to reduce unwanted transactional spam, prevent endless cycles during contract execution, and ensure market-based allocation of network resources.