Ethereum Developer Test 5

Question 1

If you engage with a smart contract and observe a 50,000 gas usage at a 15 Gwei gas cost, how much Ether would you be required to pay the miner?

Accepted Answer

750,000,000,000,000 Wei

Answer

To calculate the total Ether paid, multiply the gas usage by the gas cost: 50,000 gas * 15 Gwei/gas = 750,000 Gwei. Since 1 Gwei is 1,000,000,000 Wei (10^9 Wei), convert Gwei to Wei: 750,000 Gwei * 1,000,000,000 Wei/Gwei = 750,000,000,000,000 Wei. This conversion is crucial for understanding the actual cost in the smallest denomination of Ether.

Question 2

Which is TRUE about the Fallback function?

Accepted Answer

Can be as logical as you like, but it's best to keep it brief and not go over the 2300 gas allotment.

Answer

The fallback function in Solidity is executed when a contract receives Ether without any data, or when a function is called that doesn't exist. It has a strict gas limit of 2300 gas when called by a plain Ether transfer, making it crucial to keep its logic minimal. While it can contain logic, exceeding this gas limit will cause the transaction to fail, so brevity is key for successful Ether transfers.

Question 3

Which is TRUE about Storing almost all data in the Ethereum Blockchain?

Accepted Answer

Using a Merkle Patricia Trie

Answer

Ethereum uses a Merkle Patricia Trie (MPT) to store all state data, including accounts, balances, contract storage, and transaction receipts. This data structure is highly efficient for verifying data integrity and allows for quick retrieval and updates of information. The MPT is fundamental to Ethereum's ability to maintain a consistent and verifiable global state across all nodes.

Question 4

Solidity is assembled into

Accepted Answer

Bytecodes, which function similarly to opcodes but are executed instruction by instruction.

Answer

Solidity code is compiled into Ethereum Virtual Machine (EVM) bytecode. This bytecode consists of a series of low-level instructions, known as opcodes, which the EVM executes sequentially. Each opcode performs a specific operation, making the bytecode the executable form of the smart contract on the Ethereum blockchain.

Question 5

How much ETH was generated from 1 BTC at the start of the Ethereum token sale?

Accepted Answer

2000 ETH

Answer

During the initial two weeks of the Ethereum token sale, which began in July 2014, the exchange rate was set at 2000 ETH for every 1 BTC. This early bird rate was part of the presale structure to incentivize early participation in the network's funding. The rate subsequently decreased over the duration of the sale.

Ethereum Developer Practice Test

Ethereum Developer Practice Test

Ethereum Developer Test 5