{"id":2209,"date":"2019-12-21T10:01:00","date_gmt":"2019-12-21T09:01:00","guid":{"rendered":"https:\/\/www.codemotion.com\/magazine\/uncategorized\/solidity-hello-world-blockchain\/"},"modified":"2021-12-23T14:15:52","modified_gmt":"2021-12-23T13:15:52","slug":"solidity-hello-world-blockchain","status":"publish","type":"post","link":"https:\/\/www.codemotion.com\/magazine\/backend\/blockchain\/solidity-hello-world-blockchain\/","title":{"rendered":"Solidity: “Hello World” with the Blockchain language"},"content":{"rendered":"

In a previous article<\/a>, we introduced the basic concepts of the Ethereum Blockchain<\/strong>, including a quick overview of ERC-20 tokens<\/strong>.<\/p>\n

This article dives into Solidity<\/strong>, the programming language<\/span> used to interact with the Ethereum Blockchain. We will learn how it works, how it is translated in the Ethereum Virtual Machine<\/strong> and then executed, and which IDE<\/span> should be used to start writing code.<\/p>\n

Don’t forget to check also part three, pa<\/a>rt four<\/a> and <\/span>part five.<\/a><\/p>\n

Solidity<\/strong><\/h2>\n

The principal<\/span> and most widely known language used to write smart contracts in Ethereum is Solidity. Designed in 2014, a few months before the official launch of the Ethereum Blockchain, Solidity is now used for the Ethereum public Blockchain, as well as for private Blockchains<\/span> such as Hyperledger. As discussed in the first article of this series, Solidity is a statically-typed programming language<\/span> that runs smart contracts on the EVM, Ethereum Virtual Machine<\/strong>.<\/p>\n

Solidity is compiled of bytecode<\/strong> that is subsequently executed on the EVM. To date, there are a total of 142 valid opcodes that make up the bytecode necessary to compile any Ethereum smart contract.<\/p>\n

Another commonly used language is Vyper<\/strong>, based on Python<\/span>, but the focus of this series does not include the development<\/span> of smart contracts with Vyper.<\/p>\n

The Ethereum Virtual Machine<\/strong><\/h2>\n

On the Ethereum Blockchain, a smart contract is a simple Ethereum address with a special capability – running EVM bytecode when receiving a transaction<\/span>, which allows the performance of calculations and further transactions<\/span>.<\/p>\n

Transactions can carry a payload of 0 or more bytes of data, used to specify the type of interaction with a contract and any additional information.<\/p>\n

The smart contract begins execution on the EVM at the beginning of the bytecode: each opcode is encoded as one byte (except for PUSH<\/strong> opcodes, which have an immediate value). Every opcode is also associated with a specific gas cost. The sum of all the gas costs of a smart contract is the cost of one execution of the smart contract. Since gas cost is critical in ensuring the viability of a smart contract (an expensive-to-run smart contract is often not feasible for actual use), it\u2019s important to bear in mind<\/span> that a smart contract needs to run with the fewest possible instructions. A full list of gas costs per opcode is available here<\/a>.<\/p>\n

Interaction with a smart contract is possible with a public ABI – <\/strong>a list of supported ways a user can interact with a contract.<\/p>\n

To interact with the contract, users submit a transaction<\/span> carrying any amount of gas (even 0 is acceptable) and a data payload formatted according to the ABI, specifying the type of interaction and any additional parameters.<\/p>\n

The logical structure of a smart contract can be divided as described below:<\/p>\n