slide 22 · contracts

Smart contracts

call inc()

contract

storage

n = 1

Deploy a , call its functions, and watch and events change.

1Deploy the contract
2Call its functions
3Watch storage and events change

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amount

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Deployed

count (storage)

Total gas used

msg.sender

owner

Counter.sol

 1// SPDX-License-Identifier: MIT
 2pragma solidity ^0.8.24;
 3
 4contract Counter {
 5    address public owner;
 6    uint256 public count;
 7
 8    event Incremented(address by, uint256 newCount);
 9
10    constructor() { owner = msg.sender; }
11
12    function increment() public {
13        count += 1;
14        emit Incremented(msg.sender, count);
15    }
16
17    function reset() public {
18        require(msg.sender == owner, "not owner");
19        count = 0;
20    }
21}

A is just code plus living at an . It has no owner process, cannot run by itself, and only executes when a transaction calls it.

Interact

Emitted events (the contract's log output)

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Transaction log

waiting…

Three things to take away: writes dominate cost; every state change is re-executed and verified by every ; and events are cheap logs that front-ends read, but contracts themselves cannot read events back.