계정과 상태

Ethereum's world state is the complete snapshot of all accounts and their data at a given moment.

Every transaction transforms this state from one valid version to the next. Accounts are the building blocks of that state.

Ethereum has exactly two account types:

• Externally Owned Accounts (EOAs) — controlled by private keys (users)
• Contract Accounts — controlled by their code

Both share the same 20-byte address format.

An EOA is controlled by a private key. It can initiate transactions: send ETH or call contracts.

EOAs have no code of their own — they are simply key-controlled accounts that humans (or bots) operate.

A contract account holds code (bytecode) and storage. It has no private key and cannot start a transaction on its own.

It only acts when called by an EOA or another contract, running its code in response.

Every account stores four fields:

• nonce — transaction count (EOA) or contracts created (contract)
• balance — ETH held, in wei
• storageRoot — hash of the account's storage
• codeHash — hash of the account's code

The key distinction:

• Only EOAs can initiate transactions
• Only contracts have code and significant storage
• An EOA's codeHash is empty; a contract's is not

State changes only through transactions. A transaction can move ETH, deploy a contract, or call a contract that updates its storage.

After each block, the world state advances to a new, agreed-upon version.

All accounts are stored in a giant Merkle Patricia Trie. Its root hash — the state root — is recorded in each block header.

This single hash commits to the entire world state, just as a Merkle root commits to all transactions.

An EOA effectively exists the moment a key pair is generated — no on-chain step is needed until it transacts.

A contract account is created when a deployment transaction runs constructor code and stores the resulting bytecode.

To interact with a contract, an EOA sends a transaction specifying the contract address and the function data.

The EVM looks up the contract's code by its codeHash and executes it, possibly updating storage.

Ethereum's state is a collection of accounts. EOAs are key-controlled and initiate transactions; contracts hold code and storage and react to calls.

The state root in each block commits to all of it.

Test your accounts knowledge.

You learned that:

• Ethereum has EOAs (key-controlled) and contract accounts (code-controlled)
• Only EOAs can initiate transactions
• Each account has a nonce, balance, storageRoot, and codeHash
• The state root commits to all accounts

You have completed the Web3 fundamentals track.