# 10. ERC20s

### EIPs

* Stands for Ethereum Improvement Proposals
* These are ideas to improve L1 technology
* [eips.ethereum.org](https://eips.ethereum.org/) holds all improvement proposals

***

### ERCs

* Stands for Ethereum Request for Comments
* ERC & EIP share same number
  * ERC-20 (EIP-20)
  * It also means it is the 20th proposal

***

### ERC-20

* Token deployed on ethereum chains which follows ERC-20 token standard
* Tether, chainlink (ERC-677), unitoken, dai are examples of ERC-20 tokens

***

### Creating ERC-20 Token

#### Manual

```sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

contract ManualToken {
    uint256 initialSupply;
    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;

    // Transfer Tokens
    // Subtract "from address" amount and add "to address" amount

    function transfer(address from, address to, uint256 amount) public {
        balanceOf[from] -= amount;
        balanceOf[to] += amount;
    }

    /** Send _value tokens to _to on behalf of _from
     *
     * @param _from The address of sender
     * @param _to The address of the recipient
     * @param _value The amount to send
     *
     */
    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    ) public returns (bool) {
        require(_value <= allowance[_from][msg.sender]);
        allowance[_from][msg.sender] -= _value;
        transfer(_from, _to, _value);
        return true;
    }

    // Other Functions
}
```

#### OpenZeppelin

* Take boilerplate code from OpenZeppelin

```sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

contract MyToken is ERC20 {
    constructor(uint256 initialSupply) ERC20("MyToken", "MT") {
        _mint(msg.sender, initialSupply);
    }
}
```

***


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