Session 4 · Crypto, Bitcoin & Stablecoins FIN310

• Install MetaMask → add Sepolia network (it’s built-in → choose it from the network list).
• Use a public Sepolia faucet to get test ETH (search “Sepolia faucet”).

• Go to remix.ethereum.org → “+” New File → ClubStablecoin.sol → paste the contract below.
• In the Solidity compiler, choose version 0.8.20 (or any ^0.8.x) and compile.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

/**
 * Club Stablecoin (simple ERC-20 demo)
 * - Owner (deployer) can mint and change owner.
 * - Anyone can transfer.
 * - Anyone can burn their own tokens.
 * - Decimals = 6 (dollar-like: 1.000000)
 * NOTE: Testnet demo only. Not audited. No fees/pausing/blacklists.
 */
contract ClubStablecoin {
    string public name;
    string public symbol;
    uint8  public immutable decimals;
    uint256 public totalSupply;

    mapping(address => uint256)                     private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;

    address public owner;
    modifier onlyOwner(){ require(msg.sender == owner, "not owner"); _; }

    event Transfer(address indexed from, address indexed to, uint256 amount);
    event Approval(address indexed owner, address indexed spender, uint256 amount);
    event OwnershipTransferred(address indexed oldOwner, address indexed newOwner);

    constructor(string memory _name, string memory _symbol, uint8 _decimals){
        owner = msg.sender;
        emit OwnershipTransferred(address(0), msg.sender);
        name = _name;
        symbol = _symbol;
        decimals = _decimals; // e.g., 6 for $-style 1.000000
    }

    function balanceOf(address a) public view returns (uint256) { return _balances[a]; }
    function allowance(address a, address s) public view returns (uint256) { return _allowances[a][s]; }

    function transfer(address to, uint256 amount) public returns (bool) {
        _transfer(msg.sender, to, amount); return true;
    }
    function approve(address spender, uint256 amount) public returns (bool) {
        _approve(msg.sender, spender, amount); return true;
    }
    function transferFrom(address from, address to, uint256 amount) public returns (bool) {
        uint256 allowed = _allowances[from][msg.sender];
        require(allowed >= amount, "insufficient allowance");
        if (allowed != type(uint256).max) {
            _allowances[from][msg.sender] = allowed - amount;
            emit Approval(from, msg.sender, _allowances[from][msg.sender]);
        }
        _transfer(from, to, amount); return true;
    }

    function mint(address to, uint256 amount) public onlyOwner {
        require(to != address(0), "mint to zero");
        totalSupply += amount; _balances[to] += amount;
        emit Transfer(address(0), to, amount);
    }
    function burn(uint256 amount) public {
        uint256 bal = _balances[msg.sender]; require(bal >= amount, "insufficient");
        _balances[msg.sender] = bal - amount; totalSupply -= amount;
        emit Transfer(msg.sender, address(0), amount);
    }
    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0), "zero owner");
        emit OwnershipTransferred(owner, newOwner); owner = newOwner;
    }

    function _transfer(address from, address to, uint256 amount) internal {
        require(to != address(0), "transfer to zero");
        uint256 bal = _balances[from]; require(bal >= amount, "insufficient balance");
        _balances[from] = bal - amount; _balances[to] += amount;
        emit Transfer(from, to, amount);
    }
    function _approve(address a, address s, uint256 amount) internal {
        require(s != address(0), "approve to zero");
        _allowances[a][s] = amount; emit Approval(a, s, amount);
    }
}

• In Remix → “Deploy & Run Transactions” → Environment: Injected Provider – MetaMask → network must be Sepolia.
• Constructor args:
  • name: Campus Dollar
  • symbol: cUSD
  • decimals: 6
• Click Deploy → approve in MetaMask → copy the deployed contract address.

• As owner (the deployer), call mint(<memberAddress>, 1000000) to send 1.000000 cUSD (6 decimals) to a member.
• Repeat for a few addresses (classmates/officers).

• In MetaMask (on Sepolia), “Import tokens” → paste the contract address → symbol/decimals auto-fill → add.
• Members should now see their balances and can transfer test tokens.

• Testnet only. No public redeemability, no fundraising, no promises.
• Use small amounts; never share seed phrases; enable 2FA on exchange accounts used only for testnet.
• If you rotate leadership, use transferOwnership() to hand admin to the next treasurer (or a Safe multisig).

• Contract address on Sepolia
• 2–4 screenshots: deployment, a mint TX, and a wallet showing balance
• 1–2 paragraphs: what worked, what confused you, and one risk you’d mitigate before using anything like this in the real world