Blockchain Technology Smart Contract Fundamentals 2

Question 1

What is a 'reentrancy attack' in the context of smart contracts?

Accepted Answer

A bug where a contract calls itself recursively to drain funds before state updates

Answer

A reentrancy attack occurs when a malicious contract repeatedly calls back into the victim before the victim updates its balance, allowing repeated withdrawals.

Question 2

Which Solidity keyword prevents a function from modifying contract state?

Accepted Answer

view

Answer

'view' functions can read state but cannot modify it, while 'pure' functions cannot read or modify state at all.

Question 3

What does the ERC-20 standard primarily define?

Accepted Answer

A common interface for fungible tokens on Ethereum

Answer

ERC-20 defines a standard interface (functions like transfer, approve, allowance) for fungible tokens so wallets and exchanges can interact with any compliant token uniformly.

Question 4

In Ethereum's ABI (Application Binary Interface), what is its primary purpose?

Accepted Answer

To define how to encode and decode function calls and return values

Answer

The ABI specifies the encoding scheme for calling contract functions and interpreting their return data so external applications can interact correctly.

Question 5

What is the purpose of the 'fallback' function in a Solidity smart contract?

Accepted Answer

It is called when no other function matches the incoming call data

Answer

The fallback function executes when a call arrives that doesn't match any function selector, or when ETH is sent without call data and no receive() exists.

Blockchain Practice Test

Blockchain Practice Test

Blockchain Technology Smart Contract Fundamentals 2