Example of a smart contract

MyToken.sol

pragma solidity ^0.8.0;

contract MyToken {
    mapping(address => uint) public balanceOf;

    constructor(uint _initialSupply) {
        balanceOf[msg.sender] = _initialSupply;
    }

    function transfer(address _to, uint _value) public {
        require(balanceOf[msg.sender] >= _value);
        balanceOf[msg.sender] -= _value;
        balanceOf[_to] += _value;
    }
}