ERC-20 fungible token standard in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the ERC-20 standard in blockchain?

ERC-20 is a technical standard used for smart contracts on the Ethereum blockchain to create fungible tokens. It defines a common set of rules that all tokens must follow to be compatible with wallets and exchanges.

beginner

Name three mandatory functions defined by the ERC-20 standard.

The three mandatory functions are: <br>1. totalSupply() - returns total tokens.<br>2. balanceOf(address) - returns token balance of an address.<br>3. transfer(address, uint256) - transfers tokens to another address.

intermediate

What is the purpose of the approve and transferFrom functions in ERC-20?

<code>approve</code> allows an owner to let another address spend tokens on their behalf. <code>transferFrom</code> lets the approved address transfer tokens from the owner's account. This enables delegated transfers.

beginner

What event does an ERC-20 token emit when tokens are transferred?

The Transfer event is emitted. It logs the sender address, receiver address, and the amount of tokens transferred. This helps wallets and apps track token movements.

beginner

Why is the ERC-20 standard important for token interoperability?

Because all ERC-20 tokens follow the same rules, wallets, exchanges, and other tools can work with any ERC-20 token without special changes. This makes tokens easy to use and trade.

Which function returns the total number of tokens in an ERC-20 contract?

A totalSupply()

B balanceOf()

C transfer()

D approve()

totalSupply() returns the total tokens created by the contract.

What does the transfer function do in ERC-20?

A Returns token balance

B Transfers tokens from one address to another

C Approves spending allowance

D Creates new tokens

transfer moves tokens from the caller's address to another address.

Which event is emitted when tokens are transferred in ERC-20?

A Burn

B Approval

C Mint

D Transfer

The Transfer event logs token transfers.

What is the role of the approve function?

A To transfer tokens directly

B To check total supply

C To allow another address to spend tokens on your behalf

D To burn tokens

approve sets an allowance for delegated spending.

Why do ERC-20 tokens follow a standard?

A To ensure all tokens work with wallets and exchanges easily

B To limit token supply

C To prevent token transfers

D To make tokens unique and incompatible

The standard ensures interoperability across platforms.

Explain the key functions and events defined in the ERC-20 standard and their roles.

Think about how tokens are counted, moved, and delegated.

Describe why the ERC-20 standard is important for token usability and interoperability in the Ethereum ecosystem.

Consider how different tokens can work together smoothly.