What's a token?
- Blockchains have a native coin/token that the chain is built with. These coins/tokens are required to execute transactions, send data, are rewards for mining, etc.
- But it may be possible to encode additional metadata in the chain which represents a token.
- Depending on the chain, this can be easy or hard.
Why use tokens?
- Say you want to issue share of stocks to the many co-founders (different percentages) for your new startup company that is yet to be registered
- In the Ethereum world, you can represent the shares in the form of “tokens” that can be sold, sold back to the company, transferred, etc.
- You can create a “token contract” and deploy it in Ethereum blockchain
- Then the tokens can be transferred, sold, etc.
ERC-20 standard
- Standard for transferring tokens and approving tokens to be spent by another on-chain contract
- Details in
ERC-20 tokens
- ERC20 is a “token standard” for creating Ethereum token contracts
- ERC stands for Ethereum Request for Comments
- Any token contract that adheres to the specification follows ERC20
- Can use with any wallets that understand ERC20
- Most ICOs (Initial Coin Offerings) have adhered to ERC20
ERC-20 Interface
interface IERC20 {
function name() public view returns (string memory);
function symbol() public view returns (string memory);
function decimals() public view returns (uint8);
function totalSupply() external view returns (uint256);
function balanceOf(address owner) external view returns (uint256 balance);
function transfer(address recipient, uint256 amount) external returns (bool success);
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool success);
function approve(address spender, uint256 amount) external returns (bool success);
function allowance(address owner, address spender) external view returns (uint256 remaining);
event Transfer(address indexed sender, address indexed recipient, uint256 amount);
event Approval(address indexed owner, address indexed spender, uint256 amount);
}
ERC20 Mandatory functions
ERC20 Events
Events are only accessible by off-chain application; contracts do not have access to eventsDemo : Standard ERC20 Token Contract
ERC20 ICO
DEMO : Initial Coin Offering using ERC20
Examples of ERC-20 Tokens
