PHASE 05 Ethereum · ~4 hours

Ethereum Deep Dive

Ethereum = a global, single-threaded, deterministic VM (the EVM) whose memory is the world state and whose billing unit is gas. Once you see it that way, everything else clicks.

1. Two kinds of accounts

2. The EVM, in SWE terms

• Stack machine (256-bit words, max 1024 deep). No registers. No floats.
• Three memory regions: storage (persistent, expensive), memory (per-call, cheap), calldata (read-only input).
• Deterministic — no wall clock, no randomness, no filesystem. Only inputs: tx data + current block header + state.
• Single-threaded globally — every node runs every tx in the same order.

3. Gas — the rate limiter

Every opcode has a gas cost. ADD is 3 gas; reading a storage slot (SLOAD) is 2,100 cold / 100 warm; writing a new slot (SSTORE) is 20,000. Your tx pays gas_used × gas_price.

4. EIP-1559: base fee + tip

effective_gas_price = min(max_fee, base_fee + max_priority_fee)
// base_fee is burned, tip goes to validator

Base fee adjusts ±12.5% per block to target 50% block usage. It's an auto-scaling load balancer for blockspace — very much like AWS spot pricing.

5. A transaction's lifecycle

6. Storage layout & the state trie

Each contract has a map from 32-byte slot → 32-byte value. Solidity variables are packed into slots in declaration order. A mapping(k => v) stores v at keccak256(k || slot_index).

contract Foo {
  uint256 a;                     // slot 0
  uint128 b; uint128 c;          // slot 1 (packed)
  mapping(address => uint256) d; // slot 2 — entries at keccak256(addr || 2)
}

7. Hands-on: local chain in 5 minutes

npm init -y
npm i --save-dev hardhat
npx hardhat init           # pick "JavaScript project"
npx hardhat node           # local chain on :8545, 20 funded accounts
# in another terminal:
npx hardhat console --network localhost
> const [a,b] = await ethers.getSigners()
> (await ethers.provider.getBalance(a.address)) / 10n**18n
10000n   // 10,000 test ETH

This is your dev loop for the rest of the course. Hardhat gives you console.log inside Solidity — yes, really.

8. Reading a receipt

const tx = await contract.doThing(42);
const r  = await tx.wait();
console.log({
  status: r.status,        // 1 = success, 0 = reverted
  gasUsed: r.gasUsed,
  logs: r.logs,            // events
  blockNumber: r.blockNumber,
});

9. Project

Quiz