How to Write an Ethereum Smart Contract Using Solidity

Overview

This guide is designed for developers new to Ethereum development. We'll explore Solidity and smart contracts—their definitions, roles in Ethereum development, and walk through writing a smart contract using Solidity.

What is Ethereum?

Ethereum is a decentralized, open-source blockchain supporting Turing-complete programming languages like Solidity. Launched in 2015, it enables permissionless access, though every write operation requires payment in ETH (Gas).

What is a Smart Contract?

Coined by Nick Szabo in 1997, smart contracts are self-executing programs stored on the blockchain. They operate within the Ethereum Virtual Machine (EVM), reducing the need for intermediaries when properly audited. Ethereum’s Turing-complete nature allows nearly any operation—with associated Gas costs.

What is Solidity?

Solidity is Ethereum’s primary programming language for smart contracts, inspired by JavaScript, C++, and Python. Alternatives like Vyper exist, but Solidity remains dominant due to its widespread adoption and robust features.

Your First Smart Contract

Below is a simple Solidity contract that stores and retrieves an unsigned integer:

// SPDX-License-Identifier: MIT
pragma solidity >=0.4.0 <0.7.0;
contract SimpleStorage {
    uint storedData;
    function set(uint x) public {
        storedData = x;
    }
    function get() public view returns (uint) {
        return storedData;
    }
}

Code Breakdown:

1. SPDX License: Mitigates copyright issues (optional).
2. Pragma Directive: Specifies compiler version.
3. Contract Declaration: Named SimpleStorage.
4. Variable: storedData holds the unsigned integer.

5. Functions:

   • set(): Updates storedData (public).
   • get(): Retrieves storedData (read-only).

👉 Learn more about Solidity syntax

Deploying the Smart Contract

Tools:

• Remix IDE: Web-based Ethereum IDE.
• MetaMask: Browser extension for wallet management.
• Ropsten Testnet: Ethereum test network for deployment.

Steps:

1. Compile: Use Remix’s Solidity plugin.

2. Deploy:

   • Connect MetaMask (Ropsten network).
   • Fund wallet via Ropsten faucet.
   • Deploy via Remix’s "Injected Web3" environment.
3. Confirm Transaction: Approve via MetaMask; wait for blockchain confirmation.

FAQ Section

1. What’s the cost of deploying a smart contract?

• Costs vary by contract complexity and network Gas fees. Testnets like Ropsten use free test ETH.

2. Can I update a deployed contract?

• No. Deployed contracts are immutable. Use upgradeability patterns for modifications.

3. Why use Solidity over Vyper?

• Solidity offers more features and broader community support, while Vyper emphasizes simplicity and security.

👉 Explore Ethereum development tools

Conclusion

You’ve now written and deployed a basic Solidity smart contract! For deeper dives, refer to the Solidity documentation. Stay updated with Ethereum trends and advanced guides through community forums and newsletters.