Balance checking in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is balance checking in blockchain?

Balance checking is the process of finding out how much cryptocurrency or tokens an address holds on the blockchain.

intermediate

Which blockchain data structure stores the balance of an address?

The balance is stored in the blockchain's state, often in an account or UTXO (Unspent Transaction Output) model depending on the blockchain type.

beginner

How do you check an Ethereum address balance using Web3.js?

Use the method web3.eth.getBalance(address) which returns the balance in wei (smallest unit).

beginner

Why is balance checking important before sending a transaction?

To ensure the sender has enough funds to cover the amount and transaction fees, preventing failed transactions.

intermediate

What is the difference between checking balance on-chain vs off-chain?

On-chain balance checking reads directly from the blockchain state, while off-chain may use cached or third-party services for faster access but less trust.

What does the balance of a blockchain address represent?

A The total fees paid by the address

B The amount of cryptocurrency or tokens held by that address

C The number of transactions made by the address

D The number of smart contracts deployed by the address

The balance shows how much cryptocurrency or tokens the address currently owns.

Which method is commonly used in Web3.js to check an Ethereum address balance?

A web3.eth.getCode()

B web3.eth.sendTransaction()

C web3.eth.getTransactionCount()

D web3.eth.getBalance(address)

web3.eth.getBalance(address) returns the balance of the address in wei.

Why should you check your balance before sending a transaction?

A To confirm you have enough funds to cover the amount and fees

B To see how many transactions you have sent

C To check the network speed

D To verify the smart contract code

Checking balance prevents failed transactions due to insufficient funds.

In a UTXO-based blockchain, what does balance checking involve?

A Summing all unspent transaction outputs linked to the address

B Reading the account balance directly from the state

C Counting the number of blocks mined

D Checking the smart contract storage

UTXO blockchains track balance by summing unspent outputs for an address.

What is a downside of off-chain balance checking?

A It is slower than on-chain checking

B It requires mining new blocks

C It may not be fully up-to-date or trustable

D It uses more gas fees

Off-chain data can be cached or from third parties, so it might not reflect the latest blockchain state.

Explain how you would check the balance of a blockchain address using a programming library.

Think about how Web3.js or similar libraries provide balance info.

Describe the difference between on-chain and off-chain balance checking and why each might be used.

Consider direct blockchain queries vs third-party services.