Ethereum Blockchain Development Fundamentals
Accounts, state, and the EVM
Ethereum is a state machine: every block transitions a global state of accounts. Externally owned accounts (EOAs) are controlled by private keys and have no code; contract accounts have code and storage. Understand that balances, nonces, code, and storage are all part of account state, and that transaction nonces prevent replay. The EVM is a stack machine with 256-bit words; every operation costs gas, and gas limits protect the network from unbounded computation. Distinguish gas limit (max units allowed), gas price or base fee plus priority fee (price per unit), and the total fee actually paid (gas used times effective price).
Transactions, blocks, and finality
Know the difference between legacy and EIP-1559 transactions, and why a transaction can fail yet still consume gas. Blocks are produced by validators under proof-of-stake; a transaction is included when mined and becomes increasingly final as more blocks build on it. Logs (events) are not readable by contracts; they are for off-chain consumers.
Common traps
Questions often confuse EOAs with contracts, treat storage as free, or assume a reverted transaction refunds all gas. Others mix up block.timestamp (manipulable by validators within limits) with a reliable clock, or assume an address is an identity rather than a key hash. Remember that contract addresses are derived from sender and nonce (CREATE) or from sender, salt, and init code (CREATE2).
Rule of thumb
If a transaction reverts, state changes are undone but consumed gas is not returned. Worked example: a call with gas limit 100,000 that reverts after using 40,000 still charges for 40,000.