Blockchain CBDE BTA Certified Blockchain Developer - Ethereum Exam Practice Test

all gas is consumed

all remaining gas is returned.

its best to use a contract with public storage variables, so it can be used like a class.

it's best to use a struct, which is cheaper than deploying a new contract.

it's not possible to generate new datatypes in Solidity.

Websites that try to interface with the Token would have to know the exact ABI. It is upfront clear how the interaction has to be with the standard Interfaces.

The Ethereum Foundation can easily validate the Tokens and approve any audits by following the standard interface.

everybody can become a miner, everybody can send transactions and everything is public.

usually only a few selected nodes can be miners. Transactions can be further limited.

are a great way to circumvent gas requirements, because a loop will only consume gas once.

are dangerous when used with data structures that grow, such as arrays or mapping, because it is hard to estimate the gas requirements.

should be avoided where possible, because of unknown side-effects on the gas requirements.

are interrupting execution on error, because they throw an exception.

continuing execution on error silently, which is the reason why they are so dangerous.

returning Booleans to indicate an error during execution.

.send() throws an exception, while the other functions are returning Booleans during execution to indicate an error.

can help to engage the community in testing your smart contracts and therefore help to find bugs early.

might be a burden as it is an administrative overhead mainly.

is completely useless. Who wants to test beta-ware software? It’s better to start with the bug-bounty program after the contract is released on the main-net.

it’s good to use a push over a pull method.

it’s good to use a push and a pull method to ensure that participants can get their money no matter the contract state. In addition to and pushing it should contain a withdraw method.

it's good to use only pull and no push method.

is the reference implementation of the Ethereum protocol and every other node implementation internally uses the closed-source from Geth.

is the library that is used for the blockchain node Go-Ethereum. It is also used by Parity is parts, because it's closed source.

is one of the many blockchain nodes that implement the Ethereum Protocol. It's open source and everyone can contribute.

a Linked List with pointers to previous blocks hashes is used.

a Merkle Patricia Trie is used.

a Radix Trie is used because the Merkle Patricia Trie is too inefficient.

to move all existing logic to the blockchain, so everything runs on the same system. This way it might be more complex, but easier to maintain.

to move only those parts to the blockchain that really need the blockchain. This way smart contracts can be easier to read, easier to test and are not so complex.

to move those parts to the blockchain that deal with Ether transfers. All other parts can remain in traditional database systems. This way only the value-transfer is on the blockchain.

The Public Key is for Signing Transactions, the Private Key must be given out to verify the signature.

The Private Key signs transactions, the Public Key can verify the signature.

The Private Key is to generate a Public Key. The Public Key can sign transactions, the address is here to verify the transactions.

can't be split across multiple files, everything should be in one single file.

can be split across multiple files, but every contract must be in a file with the same name as the contract itself.

can be spread across multiple files. To import all contract from a file you can use "import 'myfile.sol'. To import Contract MyContract from myfile.sol you use "import {MyContract as SomeContract} from 'myfile.sol';".

the amount of gas your contract deployment and transactions, against your contract, will need. This way you can essentially lower the gas costs over traditional web3.js dApps.

different Networks to deploy your contracts to. This way you can easily deploy to a local blockchain, the main-net or the Ropsten/Rinkeby Test-Net with only one parameter.

you can manage your secret API keys to the Ethereum Network. This way you can get access to several different Ethereum nodes at the same time without the need to switch your keyfiles.

are stored on chain and are a great way to get a return value when a contract calls another contract.

are stored in something like a side-chain and cannot be accessed by contracts.

are used primarily for debugging exceptions in solidity.