What is the Structure of a Smart Contract in Ethereum Blockchain?

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A person is exploring the structure of a smart contract on their computer screen.
Table of Contents
A person is exploring the structure of a smart contract on their computer screen.

Key Takeaways:

  • Smart contracts consist of variables, functions, and events that enable the execution of contract terms on a blockchain
  • The structure includes data storage, memory for temporary storage and environment variables
  • View functions allow reading data from smart contracts without modifying anything, providing easy access to contract information

What is the Structure of a Smart Contract in Ethereum Blockchain?

Smart contracts consist of variables, functions, and events that enable the execution of contract terms on a blockchain.

The key components of a smart contract include the parties involved in the agreement, predefined rules and conditions that determine when actions should be executed, and digital signatures to ensure authenticity and security.

This article demystifies the complexities, breaking down key elements and structure of these ingenious programs into understandable chunks. Ready for a deep dive into the heart of smart contract technology? Let’s get started!


In the realm of smart contracts, variables play a pivotal role. They are the foundational elements that store data and enable functionality within these digital agreements. As per the rules of any programming language, Ethereum’s Solidity also has several types of variables – state and local.

State variables are stored on the blockchain itself making them permanent, while local ones exist only within a function call and then disappear. They give developers flexibility to create complex conditions for contract execution.

In an asset tokenization scenario on Ethereum platform, a variable could represent each unique token tied to a real-world asset thus bringing security via immutable ledger system in blockchain-based agreements.


Functions are a crucial component of smart contracts. They enable the execution of specific actions within the contract based on certain conditions. In simple terms, functions can be thought of as sets of instructions that perform specific tasks when triggered by transactions or other events.

These tasks can include calculations, data manipulation, and interactions with other contracts or external systems.

When writing functions in a smart contract, developers have different types to consider. One such type is view functions which allow anyone to call them without making any changes to the blockchain state.

Another important type is constructor functions that are executed only once during the deployment of a smart contract and are responsible for initializing its variables and settings.

It is worth noting that smart contracts also come with built-in functions provided by their programming language, like Solidity for Ethereum contracts. These built-in functions offer additional functionalities such as accessing time stamps or performing cryptographic operations.


Events are an essential component of smart contracts. They allow the contract to emit signals or notifications when specific conditions are met. These events serve as a way for the contract to communicate with external systems or trigger actions based on certain events happening within the contract.

An event can be emitted when a transaction is executed or when a specific function is called. Developers can then listen for these events and take appropriate actions accordingly.

Events add flexibility and enable real-time updates in smart contracts, making them more versatile and interactive. As a result, they enhance the overall functionality and usability of smart contracts in various applications on blockchain platforms like Ethereum.

Structure of a Smart Contract

The structure of a smart contract is defined by its components, which include data storage, memory, and environment variables.

Data Storage

Data storage is a crucial aspect of smart contracts. It refers to the mechanism through which information and data are stored within a contract on the blockchain. Smart contracts can store various types of data, such as numbers, strings, addresses, and arrays.

This allows for the secure and transparent management of information related to an application or agreement. By leveraging the immutability of blockchain technology, smart contracts ensure that stored data cannot be altered or tampered with once it has been recorded.

This feature provides increased security and reliability in executing contracts and agreements on decentralized platforms like Ethereum.


Memory is an essential component of a smart contract. It allows the contract to store and access data during its execution. Think of memory as a temporary storage space where the contract can hold information that needs to be accessed quickly.

This memory is volatile, meaning it gets cleared once the contract execution is completed.

Within the smart contract’s memory, variables can be declared and assigned values, such as strings or numbers. These variables can then be used in functions or calculations within the contract.

Memory also enables the manipulation of data on-the-fly during contract execution.

By utilizing memory effectively, smart contracts can efficiently process and manipulate data for various purposes, ranging from simple tasks like calculations to more complex operations involving multiple variables and conditions.

With this capability, smart contracts offer greater flexibility and functionality compared to traditional agreements.

Environment Variables

Environment variables are an essential component of smart contracts. They refer to the external state or conditions that can influence a contract’s behavior or execution. These variables provide contextual information and help determine how the contract functions under different circumstances.

In an Ethereum smart contract, environment variables could include the current block number, timestamp, gas price, or even details about other contracts on the network. By accessing these variables within their code, developers can create more dynamic and adaptable smart contracts that respond intelligently to their environment.

This capability enhances the flexibility and functionality of smart contracts while also ensuring their compatibility with evolving blockchain ecosystems.

Writing Functions in a Smart Contract

In smart contracts, functions are written to define the actions and operations that can be performed within the contract. These functions can range from simple calculations to complex business logic.

Learn more about how to write functions in a smart contract and explore real-world examples for a better understanding of their use cases. Start coding your own smart contracts today!

View Functions

View functions in a smart contract are special functions that allow users to retrieve information from the blockchain without modifying any data. These functions are read-only and do not modify the state of the contract or consume any gas.

  • View functions provide a way to access contract data without making any changes.
  • They can be called by anyone, including external applications and users.
  • View functions do not require any gas because they only read data from the blockchain.
  • These functions can return values or arrays of values back to the caller.
  • View functions cannot update the state of the contract or modify any variables.
  • By using view functions, developers can easily retrieve information from smart contracts and incorporate it into other applications or processes.

Constructor Functions

Constructor functions in smart contracts are special types of functions that are executed only once during the contract’s creation. These functions play a key role in initializing the contract’s state and defining any initial conditions or parameters. Here are some key points about constructor functions:

  1. Constructor functions have the same name as the contract.itself, making them easy to identify.
  2. They do not have a return type. as their purpose is to initialize the contract rather than returning a value.
  3. Constructor functions can have parameters, allowing for customization during contract deployment.
  4. The constructor is invoked automatically when creating an instance of the smart contract.
  5. In Solidity, the most commonly used programming language for Ethereum smart contracts, constructors are declared using the `constructor` keyword.

Built-in Functions

Built-in functions in smart contracts are pre-defined functions that are provided by the programming language used to write the contract. These functions serve specific purposes and can be called within the contract code to perform various operations. Here are some examples of built-in functions commonly used in smart contracts:

  1. assert(): Used to check for conditions that should never occur. It is typically used to validate inputs or ensure certain conditions are met before executing further code.
  2. require(): Similar to assert(), but it is used for validating user inputs or contract-specific requirements. If the condition specified in require() evaluates to false, an exception is thrown and the transaction is reverted.
  3. msg.sender: Returns the address of the account that initiated the current function call.
  4. msg.value: Returns the amount of Ether sent with the function call.
  5. block.timestamp: Returns the timestamp (in seconds) of the current block.
  6. now: A synonym for block.timestamp, returning the same value.
  7. address.balance: Returns the balance of a specific address in Wei, which is a basic unit of Ether.
  8. address.transfer(amount): Sends a specified amount of Wei from one address to another.
  9. keccak256(): Hashes its input using Keccak-256 algorithm, commonly used for generating unique identifiers or verifying data integrity.
  10. abi.encodePacked(): Concatenates multiple values into a single packed representation, useful for generating predictable hashes or efficiently storing data.

Examples of Smart Contracts

In this section, we will explore two common examples of smart contracts: the “Hello World” contract and the token contract.

Hello World

Hello World is a classic example in programming that demonstrates the basic functionality of a language or platform. In the context of smart contracts, Hello World serves as a simple contract to showcase the fundamental structure and components. Some examples of Hello World smart contracts include:

  • A contract that accepts a transaction and simply emits an event with the message “Hello, World!” This demonstrates the use of events in smart contracts.
  • A contract that stores a variable called “message” with the value “Hello, World!” This showcases the use of variables in smart contracts.
  • A contract that includes a function called “sayHello” which returns the message “Hello, World!” when invoked. This highlights the use of functions in smart contracts.
  • A contract that deploys a token on the Ethereum blockchain and initializes it with a total supply of 10,000 tokens. This illustrates how smart contracts can be used to create and manage tokens.


A token is a fundamental component of many smart contracts. It represents a unit of value or ownership within a blockchain-based system. Tokens can have various functions and properties, depending on the specific use case and application. Here are some key aspects of tokens in smart contracts:

  • Tokenization: Tokens enable the digitization and representation of real-world assets, such as currencies, commodities, or property rights. Through tokenization, these assets can be securely stored and traded on a blockchain.
  • Transferability: Tokens can be easily transferred between users within the blockchain network. This allows for seamless transactions and eliminates the need for intermediaries or third parties.
  • Ownership control: Smart contracts utilize tokens to track ownership and control over digital assets. By assigning tokens to specific addresses or accounts, ownership rights can be established and enforced automatically.
  • Utility tokens: Some tokens serve as utility tokens, granting holders access to a particular product or service within a decentralized application (dApp). These tokens often have functionalities beyond mere ownership or transferability.
  • Security tokens: Security tokens represent an investment contract that derives its value from an underlying asset. They are subject to regulatory compliance and provide investors with specific rights, such as dividends or voting power.
  • ERC20 standard: The Ethereum platform introduced the ERC20 standard for creating fungible tokens. A fungible token means that each individual token is interchangeable with others of the same type and holds equal value.
  • Tokenomics: The economics associated with a token are referred to as tokenomics. This includes factors like total supply, distribution mechanisms, inflation/deflation rules, rewards systems, and governance models.


How Are Variables and Functions Used in a Smart Contract?

Variables in a smart contract are used to store information that is accessible by the contract. They can be of various data types such as uint256 (unsigned integers) and bytes32 (byte arrays). Functions, on the other hand, define the behavior of the contract and can be used to set or retrieve information stored in the variables.

What is the Purpose of the Pragma Solidity Statement?

The pragma solidity statement is used to specify the version of the Solidity programming language that the contract is written in. It ensures that the contract is compatible with the specified version and avoids any compatibility issues.

How is the Structure of a Contract Similar to Object-Oriented Languages?

The structure of a contract in Ethereum Blockchain is similar to classes in object-oriented languages. It allows the contract to have variables and functions, just like a class would have attributes and methods.

How Are Smart Contracts Executed in Ethereum Blockchain?

Smart contracts in Ethereum Blockchain are executed when triggered by a transaction. The execution of a smart contract involves running the associated functions and updating the state variables accordingly.

What Happens When an Error Occurs During the Execution of a Smart Contract?

When an error occurs during the execution of a smart contract, an error message is generated. This error message can be used to debug and identify the cause of the error. It is important to handle errors properly in order to ensure the desired behavior of the contract.

How Does a Smart Contract Provide Information About the Blockchain?

A smart contract provides information about the blockchain by utilizing special variables that are predefined in Solidity. These variables allow the contract to access information such as the address of the sender, the block number, and the timestamp of the current block.

Can a Smart Contract Interact With Another Smart Contract?

Yes, a smart contract can interact with another smart contract. This interaction can be achieved by calling the functions of the other smart contract and passing any required arguments. The result of the interaction can be used to update the state variables of the calling contract.

Where is a Smart Contract Stored Permanently on the Blockchain?

A smart contract is stored permanently on the blockchain. It is replicated and stored on every node in the Ethereum network, ensuring its durability and accessibility.

Conclusion: Smart Contracts Architecture

By grasping the key elements and architecture of smart contracts, individuals can unlock the potential to automate agreementsincrease efficiencyimprove transparency, and reduce costs.

With their ability to securely execute contract terms on the Ethereum platform using Solidity programming language, smart contracts are revolutionizing how we approach digital transactions. Familiarizing oneself with smart contract programming opens up a world of possibilities in creating innovative solutions for various industries.



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About the Author:
Alex Sterling stands at the forefront of blockchain innovation, offering a technical perspective rooted in a Computer Science background. Specializing in decentralized systems, Alex's articles dissect blockchain technologies and crypto market trends, making intricate details comprehensible for readers. They are deeply involved in blockchain project development, frequently sharing their technical expertise at tech conferences. Alex's work aims to educate and inspire readers about the transformative potential of blockchain and cryptocurrency.