ATMs are mentioned as the oldest piece of technology that corresponds to the intelligent implementation of the contract.  The 2014 white paper on ethereum cryptocurrency describes the Bitcoin protocol as a weak version of the intelligent contract concept, as defined by computer scientist, lawyer and cryptographer Nick Szabo. From Ethereum, different cryptocurrencies support script languages that allow advanced intelligent contracts between unreliable parties.  Smart contracts should be distinguished from intelligent legal contracts. This last point concerns a traditional legally binding agreement in natural language, in which certain terms are expressed and translated into machine-readable code.    The provision of an intelligent contract on a blockchain is similar to that of a loss of value on a blockchain by sending a transaction from a portfolio to the blockchain.  The transaction contains the code compiled for the intelligent contract as well as a specific recipient address.  This transaction must then be included in a block that will be added to the blockchain, and that is when the intelligent contract code will be executed to determine the state of origin of the intelligent contract.  Error-tolerant Byzantine algorithms secure the intelligent contract in a decentralized manner through attempts to manipulate it. Once an intelligent contract has been made available, it can no longer be updated.  Smart contracts on a blockchain can record any state and perform arbitrary calculations. End customers interact with a smart contract through transactions.
Such transactions with an intelligent contract can launch other intelligent contracts. These transactions may result in a change in status and the sending of parts from one intelligent contract to another or from one account to another.  With the implementation of Ethereum in 2015, based on blockchains, the « Smart Contract » is generally used specifically in the sense of a general calculation that takes place on a blockchain or a distributed Ledger. The U.S. National Institute of Standards and Technology describes an « intelligent contract » as a « collection of codes and data (sometimes called functions and state) provided by cryptographic transactions on the blockchain network.  In this interpretation, used z.B by ethereum Foundation or IBM, an intelligent contract is not necessarily related to the conventional concept of a contract, but can be any type of computer program.