CBDE BTA Certified Blockchain Developer - Ethereum Questions and Answers

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.

safe against reentrancy because of the small gas stipend of 2300 gas.

dangerous because they send all gas along, it's better to use address.call.value()().

all gas is consumed

all remaining gas is returned.

can be destroyed using the selfdestruct keyword. This way all remaining ether will be sent to the receiver address, regardless if they have a fallback function or not.

are bound to a private key which is necessary to sign transactions outgoing from that account.

are logical opcodes running on the ethereum blockchain very similar to smart contracts.

the Metadata contains the ABI Array, which defines the Interface to interact with the Smart Contract. Metadata can also contain the address of the smart contract when it gets deployed.

metadata contains the address, and the size of the smart contract. The ABI Array is generated externally upon deploying the smart contract.

the ABI array and the Metadata are not generated when solidity is compiled to bytecode, its generated by a migration software which deploys the smart contract on the blockchain.

it's good to use the block timestamp, as this is always different.

it's good to use the block hash as this is clearly always very different.

it's good to use the RANDAO smart contract.

it's not possible to have a random number in a deterministic environment such as the Ethereum blockchain.

to deploy to the main-network as quickly as possible.

to use in-memory blockchain simulations, because mining works instantaneously.

to use a private network at all times, because this is the closest you get to the real network.

Keccack256 while internally to hash values it's easy to use the Dagger-Hashimoto to create a meaningful hash.

the Dagger-Hashimoto hashing while internally the EVM uses SHA256 which is an alias for Keccack256.

the Dagger-Hashimoto hashing while internally the EVM uses Keccack256 which is almost similar to SHA256, but has a different padding so produces different hashes.

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.

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.