CBDE Practice Exam Questions and Answers

A.  

totalSupply(), balanceOf(address), allowance(address,address), transfer(address,uint256), approve(address,uint256), transferFrom(address,address,uint256). Events: Transfer(address,address,uint256), Approval(address,address,uint256)

B.  

name(), symbol(), totalSupply(), balanceOf(address), ownerOf(uint26),approve(address,uint256), takeOwnership(uint256),transfer(address,uint256),Events: Transfer(address,address,uint256), Approval(address,address,uint256)

A.  

It helps you to find bugs, regression bugs and sometimes also helps you to understand your code from different angles.

B.  

It is a great way to spend time on something that you get paid for. But ultimately it will just slow down the development process.

A.  

to Wei, so it will send the equivalent of 10^18 Wei.

B.  

to Finney, so it will send the equivalent of 10^3 Finney.

C.  

to Szabo, so it will send the equivalent of 10^6 Szabo.

A.  

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

B.  

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

C.  

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

A.  

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

B.  

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

C.  

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.

A.  

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.

B.  

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

A.  

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

B.  

a Merkle Patricia Trie is used.

C.  

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

A.  

a function marked as pure can change the state, while a view function can only return static calls.

B.  

a function marked as view can never access state variables, while pure functions are here to return only one value.

C.  

a view function can access state variables, but not write to them. A Pure function cannot modify or read from state.

A.  

to check internal states that should never happen.

B.  

to check input arguments from users.

A.  

it always produces the same output given the same input.

B.  

it uses equally distributed data to produce the output given a long input.

C.  

it shouldn't be possible to re-generate the input given the output.