Smart Contracts 101

A smart contract is a self-executing program stored on a blockchain that automatically enforces the terms of an agreement when predefined conditions are met. The concept was first proposed by computer scientist Nick Szabo in 1994, but it wasn't until Ethereum launched in 2015 that smart contracts became widely practical.

Think of a smart contract like a vending machine: you insert the right amount of money, select your item, and the machine automatically delivers it. No middleman, no negotiation — the rules are encoded and executed automatically.

Smart contracts on Ethereum and similar platforms follow this flow:

1. Writing — A developer writes the contract logic in a programming language like Solidity (Ethereum), Rust (Solana), or Move (Sui/Aptos).

2. Compilation — The source code is compiled into bytecode that the blockchain's virtual machine can execute.

3. Deployment — The compiled contract is deployed to the blockchain via a transaction, receiving its own unique address.

4. Interaction — Users interact with the contract by sending transactions to its address, calling specific functions defined in the code.

5. Execution — The blockchain's virtual machine (e.g., EVM for Ethereum) executes the contract code. All nodes run the same code and must reach the same result.

6. State Changes — The contract can read and write data to the blockchain, transfer tokens, and interact with other contracts.

Smart contracts power a vast ecosystem of applications:

• DeFi (Decentralized Finance) — Lending protocols (Aave), decentralized exchanges (Uniswap), yield farming, and more.
• Token Creation — ERC-20 (fungible tokens) and ERC-721 (NFTs) are smart contracts that define token behavior.
• DAOs — Decentralized Autonomous Organizations use smart contracts for governance and treasury management.
• Insurance — Automated claims processing when conditions are verified (e.g., flight delay insurance).
• Supply Chain — Automated payments when goods reach specific checkpoints.
• Gaming — On-chain game logic with verifiable fairness and true ownership of in-game assets.

Immutability — Once deployed, smart contracts cannot be easily changed. Bugs can be permanent and costly (the DAO hack in 2016 resulted in $60M lost).

Oracle Problem — Smart contracts can only access on-chain data. They need "oracles" (like Chainlink) to get real-world information such as prices, weather, or sports scores.

Gas Costs — Executing contract code requires computational resources, paid for in the blockchain's native currency (gas fees on Ethereum).

Complexity — Writing secure smart contracts is challenging. Even experienced developers can introduce vulnerabilities. Auditing is essential.

Scalability — Every node must execute every smart contract call, which limits throughput on Layer 1 blockchains.