CBDE BTA Certified Blockchain Developer - Ethereum Questions and Answers

the User.

contract A.

working with either // or ///

working with /* comment */ or /** @.. natspec style */

not possible, all comments must be single-line.

using relative and absolute paths, where the "." And the ".." depict that it's a relative path.

only via GitHub using the Repository and Username.

using the special requirefile(...) statement, which looks in a specific library path to import files.

1 Ether = 10^18 wei, 10^9 Gwei, 10^3 Finney

1 Ether = 10^19 wei, 10^13 Gwei, 10^3 Finney

1 Ether = 10^16 wei, 10^13 Gwei, 10^3 Finney

1 Ether = 10^18 wei, 10^6 Gwei, 10^6 Finney

for which compiler version a smart contract was developed for. It helps to avoid breaking changes.

for which blockchain a smart contract was developed for. It helps to avoid confusion with beta-customers.

for which blockchain node a smart contract was developed for. It helps to avoid mixing up different versions of go-ethereum.

all public state variables and properties, public and internal functions and modifiers.

all public and private state variables, public, internal and external functions, but not modifiers

all public state variables and properties, public functions and modifiers, but not internal, external or private ones.

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.

2, because the decimal is truncated.

3, because it's always rounded.

2.5, because it's automatically converted into a float.

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.

can only be accessed during calls.

can be accessed during transactions and calls.

great, because they cut the middle man, run on a trusted platform, apply logic to the blockchain where already economic assets are running and thus allow peer to peer trade.

an amazing way to create new applications. Those applications run entirely separated from other applications on the platform and allow for logical interactions. They can't access any funds to add an additional layer of trust.

a new way of applying logical operations for banks and big financial institutions. This way they can reduce the staff while operating at increased security.

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.