= 0.7.0 < 0.9.0Structure of a Smart ContractThe structure of a smart contract can vary depending on the programming language and blockchain platform used, but in general, a smart contract can be broken down into the following components:Variables: Variables store the data and state of the contract, they can be of different types (e.g. integers, strings, boolean, etc.).Functions: Functions are the building blocks of a smart contract, they are used to execute certain actions or calculations, they can be public, private or internal.Modifiers: Modifiers are used to change the behavior of functions based on certain conditions, they can be used to check if a user has the necessary permissions to execute a certain action, or to enforce certain rules on the contract's variables.Events: Events allow for the contract to emit a message that is recorded on the blockchain and can be listened to by external parties, they can be used to track changes in the state of the contract, or to inform external parties of certain actions that have occurred.Constructor: A constructor is a special function that is executed when a smart contract is created, it can be used to set the initial state of the contract, or to perform any other necessary setup tasks.Fallback function: A fallback function is a special function that is executed when a contract receives a transaction without any data or a function signature.Library: Library is a collection of functions that can be imported by the contract to be reused, libraries can be a way to separate concerns and make the contract more readable.Inheritance: Smart contract can inherit properties and behaviors from other contracts, it allows the use of reusable code, and it can be used to make smart contracts more modular.This is a general overview of the different components that a smart contract might include, depending on the requirements of the specific use case and the programming language used. Complex smart contracts can include multiple functions, variables, and other components, and can even call other smart contracts.Layout of Solidity Source fileIn Solidity, a source file generally has the following layout:Pragma statement: A pragma statement specifies the version of the Solidity compiler that should be used to compile the code. It is generally the first line of the source file and has the following format: pragma solidity ;Import statements: Import statements are used to include other source files or libraries in the current file. The syntax for an import statement is: import "filename";Contract definition: A contract in Solidity is defined using the "contract" keyword, followed by the name of the contract. Within the contract definition, various functions and variables can be defined.Function definitions: Functions are defined within the contract definition and have the following format: function () { }Variable definitions: Variables are defined within the contract definition and have the following format: = ;Note that not all of these components are necessary, and a solidity contract can be as simple as just a contract definition with no functions or variables defined or can be as complex as a contract that imports multiple libraries, defines multiple functions and variables, and uses many modifiers and visibility levels.Since making source code available always touches on legal problems with regards to copyright, the Solidity compiler encourages the use of machine-readable SPDX license identifiers. Every source file should start with a comment indicating its license: // SPDX-License-Identifier: MITThe compiler does not validate that the license is part of the list allowed by SPDX, but it does include the supplied string in the bytecode metadata.Related QuestionsHow smart contracts work?Smart Contracts are self-executing digital agreements that are written in a programming language called Solidity. Here's a more detailed explanation of how smart contracts work in Ethereum:The terms of the contract are defined and written in Solidity code. The code is then compiled and deployed to the Ethereum network.When a user wants to execute the contract, they send a transaction to the Ethereum network, which includes the address of the deployed smart contract and any data or parameters required to execute the contract.The Ethereum network then processes the transaction, which triggers the code of the smart contract to run on the nodes of the network.The code checks the conditions set out in the contract and if they are met, executes the terms of the contract automatically. This can include updating the state of the Ethereum blockchain, such as transferring digital assets, updating data stored in the contract, or triggering other smart contracts.As the smart contract is stored on the Ethereum blockchain, the terms of the contract and its execution are transparent and visible to all parties involved.The execution of the smart contract is recorded in a block and added to the Ethereum blockchain, providing immutability and transparency.The smart contract can also be called by other smart contract, it can be reused and can be connected to other decentralized applications.In Ethereum, smart contracts are executed by the Ethereum Virtual Machine (EVM) on the nodes of the network. The EVM runs the bytecode of the smart contract and updates the state of the blockchain accordingly. Gas is used to pay for the computation of the contract and the execution of it.What are the Benefits of Smart Contract?Smart contracts offer a number of benefits, including:Automation: Smart contracts can automatically execute the terms of a contract when certain conditions are met, without the need for human intervention. This can help to reduce the risk of fraud, errors, and delays.Transparency: Smart contracts are stored on a decentralized blockchain, which means that the terms of the contract and its execution are visible to all parties involved. This helps to increase transparency and trust between parties.Cost savings: Smart contracts can help to reduce the cost of transactions by eliminating intermediaries, such as lawyers and banks, and by automating many of the processes involved in a contract.Security: Smart contracts are stored on a decentralized blockchain and can be programmed to execute only when certain conditions are met. This helps to increase security and reduce the risk of fraud and hacking.Decentralization: Smart Contracts enables P2P interactions and it does not require a central point of control, which can help to increase decentralization and reduce the need for trusted intermediaries.Auditability: Smart contracts are stored on a decentralized and open-source blockchain, this allows auditing of the contract by anyone without the need of a centralized intermediary.Accessibility: Smart Contracts can be coded to be self-executing and self-enforcing. this allows parties to interact and transact without prior knowledge or trust between parties.In summary, Smart contracts are self-executing digital agreements with the terms of the agreement between buyer and seller being directly written into lines of code. They have the ability to automate processes, increase transparency, reduce costs, and improve security, decentralization and auditability of transactions.* The material and content uploaded on this website are for general information and reference purposes only and don't copy the answers of this website to any other domain without any permission or else copyright abuse will be in action.Please do it by your own first!" />= 0.7.0 < 0.9.0Structure of a Smart ContractThe structure of a smart contract can vary depending on the programming language and blockchain platform used, but in general, a smart contract can be broken down into the following components:Variables: Variables store the data and state of the contract, they can be of different types (e.g. integers, strings, boolean, etc.).Functions: Functions are the building blocks of a smart contract, they are used to execute certain actions or calculations, they can be public, private or internal.Modifiers: Modifiers are used to change the behavior of functions based on certain conditions, they can be used to check if a user has the necessary permissions to execute a certain action, or to enforce certain rules on the contract's variables.Events: Events allow for the contract to emit a message that is recorded on the blockchain and can be listened to by external parties, they can be used to track changes in the state of the contract, or to inform external parties of certain actions that have occurred.Constructor: A constructor is a special function that is executed when a smart contract is created, it can be used to set the initial state of the contract, or to perform any other necessary setup tasks.Fallback function: A fallback function is a special function that is executed when a contract receives a transaction without any data or a function signature.Library: Library is a collection of functions that can be imported by the contract to be reused, libraries can be a way to separate concerns and make the contract more readable.Inheritance: Smart contract can inherit properties and behaviors from other contracts, it allows the use of reusable code, and it can be used to make smart contracts more modular.This is a general overview of the different components that a smart contract might include, depending on the requirements of the specific use case and the programming language used. Complex smart contracts can include multiple functions, variables, and other components, and can even call other smart contracts.Layout of Solidity Source fileIn Solidity, a source file generally has the following layout:Pragma statement: A pragma statement specifies the version of the Solidity compiler that should be used to compile the code. It is generally the first line of the source file and has the following format: pragma solidity ;Import statements: Import statements are used to include other source files or libraries in the current file. The syntax for an import statement is: import "filename";Contract definition: A contract in Solidity is defined using the "contract" keyword, followed by the name of the contract. Within the contract definition, various functions and variables can be defined.Function definitions: Functions are defined within the contract definition and have the following format: function () { }Variable definitions: Variables are defined within the contract definition and have the following format: = ;Note that not all of these components are necessary, and a solidity contract can be as simple as just a contract definition with no functions or variables defined or can be as complex as a contract that imports multiple libraries, defines multiple functions and variables, and uses many modifiers and visibility levels.Since making source code available always touches on legal problems with regards to copyright, the Solidity compiler encourages the use of machine-readable SPDX license identifiers. Every source file should start with a comment indicating its license: // SPDX-License-Identifier: MITThe compiler does not validate that the license is part of the list allowed by SPDX, but it does include the supplied string in the bytecode metadata.Related QuestionsHow smart contracts work?Smart Contracts are self-executing digital agreements that are written in a programming language called Solidity. Here's a more detailed explanation of how smart contracts work in Ethereum:The terms of the contract are defined and written in Solidity code. The code is then compiled and deployed to the Ethereum network.When a user wants to execute the contract, they send a transaction to the Ethereum network, which includes the address of the deployed smart contract and any data or parameters required to execute the contract.The Ethereum network then processes the transaction, which triggers the code of the smart contract to run on the nodes of the network.The code checks the conditions set out in the contract and if they are met, executes the terms of the contract automatically. This can include updating the state of the Ethereum blockchain, such as transferring digital assets, updating data stored in the contract, or triggering other smart contracts.As the smart contract is stored on the Ethereum blockchain, the terms of the contract and its execution are transparent and visible to all parties involved.The execution of the smart contract is recorded in a block and added to the Ethereum blockchain, providing immutability and transparency.The smart contract can also be called by other smart contract, it can be reused and can be connected to other decentralized applications.In Ethereum, smart contracts are executed by the Ethereum Virtual Machine (EVM) on the nodes of the network. The EVM runs the bytecode of the smart contract and updates the state of the blockchain accordingly. Gas is used to pay for the computation of the contract and the execution of it.What are the Benefits of Smart Contract?Smart contracts offer a number of benefits, including:Automation: Smart contracts can automatically execute the terms of a contract when certain conditions are met, without the need for human intervention. This can help to reduce the risk of fraud, errors, and delays.Transparency: Smart contracts are stored on a decentralized blockchain, which means that the terms of the contract and its execution are visible to all parties involved. This helps to increase transparency and trust between parties.Cost savings: Smart contracts can help to reduce the cost of transactions by eliminating intermediaries, such as lawyers and banks, and by automating many of the processes involved in a contract.Security: Smart contracts are stored on a decentralized blockchain and can be programmed to execute only when certain conditions are met. This helps to increase security and reduce the risk of fraud and hacking.Decentralization: Smart Contracts enables P2P interactions and it does not require a central point of control, which can help to increase decentralization and reduce the need for trusted intermediaries.Auditability: Smart contracts are stored on a decentralized and open-source blockchain, this allows auditing of the contract by anyone without the need of a centralized intermediary.Accessibility: Smart Contracts can be coded to be self-executing and self-enforcing. this allows parties to interact and transact without prior knowledge or trust between parties.In summary, Smart contracts are self-executing digital agreements with the terms of the agreement between buyer and seller being directly written into lines of code. They have the ability to automate processes, increase transparency, reduce costs, and improve security, decentralization and auditability of transactions.* The material and content uploaded on this website are for general information and reference purposes only and don't copy the answers of this website to any other domain without any permission or else copyright abuse will be in action.Please do it by your own first!" />

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Blockchain Essentials | Part 2

Blockchain Essentials | Part 1