Ethereum Virtual Machine (EVM): Core Definitions and Architecture

Introduction to EVM

The Ethereum Virtual Machine (EVM) is a stack-based virtual machine that executes bytecode instructions to modify the blockchain state. It operates within a defined execution environment and handles 140 instructions across 11 categories.

Key Insight:
The EVM is a quasi-Turing complete machine due to gas limitations, which cap the total computational operations. Its logic is formalized by the code execution function (Ξ):
\((\boldsymbol{\sigma}', g', A, \mathbf{o}) \equiv \Xi(\boldsymbol{\sigma}, g, I)\)
Here, σ = state, g = available gas, I = execution environment; σ' = updated state, g' = remaining gas, A = accrued substate, o = output.

EVM Implementation Logic

Core Definitions
- Environment, instruction set, and EVM state specifications.
Contract Bytecode Execution
- Parses bytecode into instructions and executes them sequentially.
- Steps:
  - Instruction Execution: Decodes, charges gas, and executes.
  - Stack Operations: Manages 256-bit words (max depth: 1024).
  - Memory Operations: Handles reads/writes and allocations.
  - Control Flow: Handles jumps (JUMP, JUMPI) and termination (STOP, RETURN).
State Modifications
- Processes gas payments, cleans empty accounts, and updates storage.

Core Definitions

Instruction Set

EVM supports 140 instructions, including:

Arithmetic: ADD, SUB, MUL, EXP (gas: VeryLowTier).
Bitwise Logic: AND, OR, SHL (EIP-145).
System Operations: CREATE2 (EIP-1014), DELEGATECALL.

Example: ADD Instruction

Bytecode: 0x01
Stack: Pops 2 operands, pushes 1 result.
Gas Cost: 3 (VeryLowTier).

ADD(0x01, 2, 1, VeryLowTier)

Execution Environment (I)

Ia: Executing account address.
Id: Input data (e.g., transaction payload).
Iv: Transferred value (wei).
IH: Current block header.

Note: For contract calls, Ib = target contract code; for creations, Ib = init code.

EVM State (μ)

Memory: Byte-addressable, zero-initialized (μm).
Stack: 1024-depth, 256-bit words (μs).
Gas: μg = gasLimit - gasUsed.
Program Counter: Starts at 0 (μpc).

Transaction Substate

Self-Destruct Set (As): Accounts marked for deletion.
Logs (Al): Indexable events for DApps.
Gas Refunds (Ar): Reimbursed for storage cleanup.

FAQs

Q1: How does gas limit EVM computations?
A1: Each instruction consumes gas (μg). Exhaustion halts execution, preventing infinite loops.

Q2: What’s the role of CREATE2?
A2: Predictably generates contract addresses, enabling counterfactual deployments.

Q3: Why is the stack depth limited?
A3: Prevents resource exhaustion attacks (max: 1024 items).

👉 Explore EVM Opcodes in Depth
👉 Master Smart Contract Development

Keywords: Ethereum Virtual Machine, EVM opcodes, gas computation, smart contracts, bytecode execution, stack-based VM, EIP standards, transaction substate.


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