Ethereum Smart Contract Basics Quiz

1. What is the primary function of a smart contract?

• To print copies of a contract for legal purposes.
• To serve as a physical representation of a contract.
• To manually negotiate contract terms between parties.
• To execute the terms of a contract automatically after specific conditions are met.

2. What technology serves as the foundation for smart contracts?

• Data storage systems.
• Cloud computing platforms.
• Blockchain technology.
• Traditional databases.

3. How are transactions verified and recorded in a blockchain?

• By a central authority approving each transaction.
• By using traditional banking systems to confirm transactions.
• Through random selection of transactions to process.
• Through a consensus mechanism by multiple nodes in the network.

4. What is the purpose of the Ethereum Virtual Machine (EVM)?

• To execute smart contracts according to the rules programmed by developers.
• To create new cryptocurrencies for trading.
• To store user data securely on the blockchain.
• To manage user identities and access permissions.

5. In which programming language are smart contracts typically written?

• Solidity
• Ruby
• Java
• Python

6. What is the nature of Solidity in relation to JavaScript?

• Solidity is a low-level, assembly language used for blockchain coding.
• Solidity is a database management system designed for JavaScript integration.
• Solidity is a game development framework that relies on JavaScript syntax.
• Solidity is a high-level, object-oriented language similar to JavaScript.

7. What are the key components of a smart contract?

• Coding, conditions, and execution.
• Data encryption, approval process, and verification.
• Manual intervention, user agreements, and logging.
• User interface, transaction fees, and processing speed.

8. How are smart contracts deployed onto the blockchain network?

• Using cryptography encryption.
• Through HTTP requests.
• Via physical delivery methods.
• By email transmission.

9. What happens when predefined conditions are met in a smart contract?

• The smart contract reverts to the initial state.
• The smart contract needs manual approval to proceed.
• The smart contract fails to operate entirely.
• The smart contract automatically executes the terms of the agreement.

10. How does the blockchain network validate the execution of a smart contract?

• By requiring users to manually approve each transaction on the network.
• By checking if the smart contract is written in Solidity language.
• By ensuring that the terms of the agreement have been met and that the transaction is valid.
• By confirming the identity of the contract creator using multi-signature.

11. What is the result of a transaction being validated in a smart contract?

• The transaction is recorded on the blockchain as an immutable record.
• The transaction is sent back to the sender for approval.
• The transaction is reversed and not recorded.
• The transaction is deleted from the blockchain permanently.

12. How do smart contracts settle transactions?

• By verbally confirming each transaction with the users involved.
• By manually approving transactions through centralized authorities.
• By transferring the agreed-upon assets or funds to the respective parties.
• By issuing paper contracts for all parties involved.

13. What is the role of the Ethereum Virtual Machine (EVM) in smart contract execution?

• The EVM only validates smart contracts without executing them.
• The EVM stores all data related to smart contracts permanently.
• The EVM manages transaction fees for users in Ethereum.
• The EVM compiles smart contracts into bytecode for execution on the blockchain.

14. What are the common data types in Solidity?

• DECIMAL, lists, and pointer
• FLOAT, characters, and variable
• UINT, strings, and address
• LONG, arrays, and object

15. How do smart contracts handle data storage?

• Smart contracts only use temporary memory for data storage.
• Smart contracts use storage, transient storage, memory, and the stack for data storage.
• Smart contracts do not handle data storage; they rely on user input only.
• Smart contracts store all data on external servers.

16. What is the difference between storage and transient storage in smart contracts?

• Storage requires additional gas fees, while transient storage does not incur any costs.
• Storage is only accessible by the contract owner, while transient storage is open to all users.
• Storage is persistent between function calls and transactions, while transient storage is reset at the end of each transaction.
• Storage is temporary, while transient storage is permanent after execution.

17. How does memory work in smart contracts?

• Memory allows for unlimited read and write operations without byte restrictions.
• Memory is structured in hierarchical layers and has no size limits.
• Memory is linear and can be addressed at a byte level, but reads are limited to a width of 256 bits.
• Memory is accessed only through external calls from other contracts.

18. What happens if a contract creation transaction does not have a recipient?

• The transaction creates a new contract with an address derived from the sender and its number of transactions sent.
• The contract is sent to a null address, causing it to disappear.
• A regular transaction occurs, ignoring the contract creation.
• The transaction fails and is reversed automatically.

19. How are functions in a smart contract accessed?

• Functions can only be accessed by their hash value.
• Functions can only be accessed from external contracts.
• Functions must be called through a complex indexing system.
• Functions can be accessed directly via their name without the `this.` prefix.

20. What is the purpose of the `require` statement in a smart contract?

• To encrypt sensitive information within the contract.
• To transfer ownership of the smart contract.
• To permanently store data on the blockchain.
• To ensure that specific conditions are met before executing a function call.

21. How does a smart contract handle errors?

• Smart contracts automatically fix any errors encountered during execution.
• Smart contracts log errors for future review but do not affect execution.
• Smart contracts ignore errors and continue executing all transactions.
• Smart contracts use `require` statements to revert all changes if certain conditions are not met.

22. What is the role of the `msg.sender` variable in a smart contract?

• `msg.sender` is the total balance of the contract.
• `msg.sender` is the address where the current external function call came from.
• `msg.sender` is the previous block`s hash.
• `msg.sender` is the gas cost of the transaction.

23. How can a smart contract be tested before deployment?

• Smart contracts can be tested using a centralized server for efficiency.
• Smart contracts can be tested only through manual debugging in the programming environment.
• Smart contracts can be tested on an Ethereum Testnet to ensure they function as intended.
• Smart contracts can be tested by deploying them on the mainnet immediately.

24. What is the significance of immutability in smart contracts?

• Immutability means that the contract must be rewritten if changes are needed.
• Immutability only protects the contract`s code, not the data it processes.
• Once a smart contract is posted on the blockchain, it becomes an immutable record where tampering is easily detected.
• Immutability allows for contracts to be edited easily if errors are found.

25. How do oracles provide data to smart contracts?

• Oracles restrict data access to only a few smart contracts for security.
• Oracles manually enter data into smart contracts using forms.
• Oracles use physical documents to inform smart contracts about external events.
• Oracles provide `trusted` data to smart contracts through transactions, allowing them to perform actions based on approved data.

26. What is the purpose of whitelisting in smart contracts?

• Whitelisting allows only approved entities to interact with the smart contract.
• Whitelisting sets a price list for services offered by the contract.
• Whitelisting generates random hash values for transactions.
• Whitelisting establishes time limits for contract execution.

27. How can the integrity of a smart contract be ensured?

• Programming in multiple languages.
• Ignoring potential vulnerabilities.
• Testing the code in an Ethereum Testnet.
• Using traditional legal contracts.

28. What is the difference between internal and external functions in Solidity?

• Internal functions can only read data, while external functions can write data.
• Internal functions can be invoked from inside the contract, while external functions can be called from any contract.
• Internal functions are private, while external functions are public only.
• Internal functions are for state changes, while external functions handle logging.

29. How do smart contracts handle array operations?

• Smart contracts can only append elements to arrays without deletion.
• Smart contracts handle arrays by using external storage only.
• Smart contracts cannot perform any operations on arrays.
• Smart contracts can delete elements from arrays using functions like `delete` or `reduction of length`.

30. What is the significance of unit testing in smart contract development?

• Unit testing is used to improve the user interface of smart contracts.
• Unit testing guarantees that no bugs exist in the smart contract.
• Unit testing helps check whether a smart contract works as intended by testing its different components.
• Unit testing allows developers to deploy contracts directly on the mainnet.