Ethereum Solidity Programming Language Quiz

1. What is Solidity?

• Solidity is an object-oriented, high-level programming language for smart contracts.
• Solidity is a networking protocol for blockchain communication.
• Solidity is a database system for storing data on the cloud.
• Solidity is a markup language for web design and development.

2. What is the relationship between Solidity and the Ethereum Virtual Machine (EVM)?

• Solidity is a storage layer for the EVM`s primary functions.
• Solidity and the EVM are completely separate systems without interaction.
• Solidity code is compiled into bytecode that the EVM understands and executes.
• The EVM translates Solidity directly into high-level commands.

3. How do you ensure the reentrancy safety of your smart contracts?

• Optimize code to minimize gas usage during transactions.
• Increase the gas limit to handle multiple calls efficiently.
• Use checks-effects-interaction patterns or reentrancy guards to prevent reentrancy attacks.
• Use external calls to communicate only with trusted contracts.

4. What is the default visibility of state variables in Solidity?

• Public.
• External.
• Internal.
• Private.

5. Are private variables really private in Solidity?

• Private variables are stored off-chain for better security.
• Yes, private variables are completely secure and hidden from all.
• Private variables can only be accessed by the contract owner.
• No, private variables are not really private as they can be read by anyone using blockchain analysis tools.

6. How to deal with private data in Solidity?

• Either don’t put private data on the blockchain or put hashes.
• Use a centralized server for private data management.
• Store private data in public variables instead.
• Always encrypt private data before storing it.

7. What are the three data types you use often in Solidity, and why?

• int, pointer, character
• uint, address, string
• bool, ref, list
• float, map, text

8. What are the two container types in Solidity?

• Objects and sets.
• Lists and dictionaries.
• Mapping and arrays.
• Tuples and structs.

9. How does the EVM understand Solidity?

• The EVM ignores bytecode completely.
• The EVM understands and executes bytecode.
• The EVM identifies Solidity through comments.
• The EVM directly executes Solidity code.

10. What is the EVM bytecode?

• A series of EVM elementary instructions called opcodes.
• A programming library for building smart contracts.
• A collection of Solidity code snippets for developers.
• A type of database used in Ethereum.

11. How to manage dates in Solidity?

• Use `string` variables.
• Use `uint` variables.
• Use `mapping` data types.
• Use `byte` arrays.

12. How to have the current timestamp in seconds in Solidity?

• Use the `timestamp` function.
• Use the `now` keyword.
• Use the `currentTime()` method.
• Use the `block.timestamp` variable.

13. How to construct a timestamp of 1 day in the future in Solidity?

• `now + 86400`
• `now + 600`
• `now + 14400`
• `now + 3600`

14. What are the different ether units available in Solidity?

• Megaether, gigaether, centiether, deciether.
• Wei, kwei, gwei, mwei, microether, milliether, ether.
• Nanoether, picoether, femtoether, zeptoether.
• Teraether, petaether, exaether, zettaether.

15. What time units are available in Solidity?

• Second, minute, hour, day, week.
• Tenth, twenty, fifty, hundred.
• Hour, fortnight, leap, millennium.
• Month, year, decade, century.

16. What are storage variables in Solidity?

• Storage variables cannot be modified after creation.
• Storage variables are only accessible within a function`s scope.
• Storage variables are permanent and stored on the blockchain.
• Storage variables are temporary and lost after execution.

17. What is a gas limit in Solidity?

• The maximum amount of gas a user is willing to spend on a transaction.
• The length of time a transaction can take.
• The total storage used by a smart contract.
• The number of functions in a contract.

18. What happens if a transaction requires more gas than the specified gas limit in Solidity?

• The transaction will be paused until more gas is provided.
• The transaction will be reverted, and the used gas will not be refunded.
• The transaction will succeed, and the excess gas will be returned.
• The transaction will proceed with a lower gas price.

19. What happens if a transaction requires less gas than the specified gas limit in Solidity?

• The gas limit will be automatically increased.
• The remaining gas will be returned to the user.
• The transaction will be delayed until more gas is provided.
• The transaction will fail, and all gas will be consumed.

20. What is a variable in Solidity?

• A method to compile code into bytecode for the EVM.
• A storage location that can contain values, which can be changed during runtime.
• A fixed value that cannot be altered throughout execution.
• A special function for executing tasks in contracts.

21. What are the different types of variables in Solidity?

• Global variables and session variables.
• Temporary variables and cache variables.
• Constant variables and dynamic variables.
• State variables and local variables.

22. What is the difference between public and private visibility modifiers in Solidity?

• Public allows access only for the owner; private is shared across all contracts.
• Public is for internal use only; private can be accessed by anyone.
• Public is accessible from any contract; private is only accessible within the contract itself.
• Public is only accessible within derived contracts; private is accessible externally.

23. What is assert in Solidity?

• Used to validate user input only.
• A method for storing temporary variables.
• A function to set default values in contracts.
• Used to check for code and should never be false.

24. What is require in Solidity?

• Used to validate inputs and conditions before execution.
• Used to manage access control in contracts.
• Used to execute complex mathematical operations.
• Used to define variables for storage purposes.

25. How to calculate Ethereum gas cost in Solidity?

• Total gas fees = gasLimit / gasPrice per unit.
• Total gas fees = gasLimit – gasPrice per unit.
• Total gas fees = gasLimit * gasPrice per unit.
• Total gas fees = gasLimit + gasPrice per unit.

26. What is a proxy contract in Solidity?

• A guide for enhancing the performance of the EVM during smart contract execution.
• A protocol for creating decentralized applications directly on the Ethereum network.
• A method to permanently store data on the blockchain without any intermediaries.
• A design pattern that employs a secondary contract to act as an intermediary between users and the main contract for storage optimization purposes.

27. What is a staking pool in Solidity?

• A set of rules for creating decentralized applications on Ethereum.
• A smart contract that allows users to pool their cryptocurrency holdings together and participate in various blockchain activities like PoS consensus.
• A digital wallet for storing multiple types of cryptocurrencies securely.
• A visual interface for users to trade cryptocurrencies easily and quickly.

28. How to write a simple Solidity smart contract for storing and retrieving data?

• Implement complex data analytics and machine learning algorithms directly in the contract.
• Use a web3 interface to link data to external databases for smart contract function.
• Create event listeners and access external APIs to manage data storage.
• Define variables, write functions (storing and retrieving data), and use visibility modifiers (public/private) for data access control.

29. How do tokens function within a Solidity smart contract?

• Tokens are generated through network consensus and cannot be traded.
• Tokens are only used for staking and cannot be transferred.
• Tokens serve as a measure for transaction fees in the contract.
• Tokens represent ownership of digital assets and can be transferred within a contract.

30. What is the ERC-20 token standard?

• A database format for storing user data securely on the blockchain.
• A protocol for creating decentralized exchanges and trading platforms.
• A standard for creating non-fungible tokens only on the Ethereum blockchain.
• A common interface for token functionality that defines how tokens can be transferred and managed within a smart contract.