Ethereum Flashcards

What is the purpose of the Ethereum Virtual Machine (EVM) opcode SLOAD?

Answer: Load a value from contract storage into the stack

SLOAD reads a 32-byte word from the contract's persistent storage slot into the execution stack.

Which Ethereum upgrade introduced the concept of 'difficulty bomb' to encourage migration to Proof of Stake?

Answer: Byzantium

Byzantium (2017) included EIP-649, which delayed the difficulty bomb and reduced block rewards from 5 to 3 ETH.

In Ethereum's account model, what differentiates an Externally Owned Account (EOA) from a contract account?

Answer: EOAs have no associated code and are controlled by private keys

EOAs have no code field and are controlled exclusively by whoever holds the corresponding private key.

What does the Ethereum Yellow Paper define as the 'world state'?

Answer: A mapping of addresses to account states including balance, nonce, storage, and code

The world state is a Merkle Patricia Trie that maps 20-byte addresses to account state objects.

Which EIP introduced the 'BASEFEE' opcode, allowing contracts to read the base fee of the current block?

Answer: EIP-3198

EIP-3198 added the BASEFEE opcode so smart contracts can access the current block's base fee directly.

In a Merkle Patricia Trie used by Ethereum, what node type stores a single key-value pair with a non-shared path?

Answer: Leaf node

Leaf nodes encode the remaining path and the terminal value, representing the end of a unique trie path.

What is 'uncle rate' in pre-Merge Ethereum and why was it significant?

Answer: The fraction of valid blocks not included in the main chain, indicating network latency and miner competition

High uncle rates indicated propagation delays; uncle blocks received partial rewards to reduce wasted PoW work.