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What Is a Smart Contract?
A smart contract is code on a blockchain that runs automatically when conditions are met.
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AiTechWorlds
AiTechWorlds
A smart contract is self-executing code stored on a blockchain that runs automatically when conditions are met. This visual guide explains how smart contracts work, Solidity, gas, deployment, common vulnerabilities, and real-world uses in DeFi and NFTs.
A smart contract is code on a blockchain that runs automatically when conditions are met.
The contract executes exactly as written, with no middleman.
Users send a transaction that triggers the contract’s functions.
Ethereum popularized programmable blockchains with smart contracts.
Solidity is the most common language for writing Ethereum contracts.
Deployment publishes the code to the blockchain at an address.
Gas is the fee paid to run contract operations on the network.
Contracts hold on-chain data that anyone can read.
Functions change state; events log actions for apps to read.
The Ethereum Virtual Machine runs contract code across all nodes.
ERC-20 and ERC-721 standards define tokens and NFTs.
Lending, swapping, and staking run on smart contracts.
NFTs use contracts to track unique ownership.
Deployed contracts usually can’t be changed — bugs are permanent.
A classic exploit where a contract is called back before it finishes.
Overflows, bad access control, and logic bugs cause big losses.
Security audits and testing reduce costly mistakes.
Oracles feed real-world data into contracts safely.
Proxy patterns allow controlled upgrades despite immutability.
Safer languages and tooling are making contracts more reliable.
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