Legenda (Yellow Paper)

• μ: state machine (g, pc, m, i, s) - EVM state
• I: execution environment
• A: Accrued substate - changes scheduled for when the tx ends (s, l, t, r, a, K)
• σ: world state, the state of the blockchain
• δ: number of items popped out of the stack
• α: number of items pushed into the stack
• w: the current opcode
• C: the cost function

How does it work?

The EVM behaves as a mathematical function would: Given an input, it produces a deterministic output. It therefore is quite helpful to more formally describe Ethereum as having a state transition function:

Y(S, T)= S'

Given an old valid state (S) and a new set of valid transactions (T), the Ethereum state transition function Y(S, T) produces a new valid output state S'.

State

The state is a giant data structure called a modified Merkle Patricia Trie, which keeps all accounts linked by hashes and reducible to a single root hash stored on the blockchain.

Transactions

Transactions are cryptographically signed instructions from accounts.