EVM (Ethereum Virtual Machine) Explained: A Comprehensive Guide for Blockchain Developers

A smart contract is computer code built into the blockchain cryptocurrency network that computers or nodes execute, and once executed, they update the ledger. The core concept is 'if this then that' logic - when a pre-existing event is triggered, the next action executes automatically. This is analogous to a vending machine: you put in money (trigger), and the machine automatically dispenses the product (executes the next action). The smart contract runs on all computers and nodes in the system, automatically updating a transparent ledger that everyone can see.

Smart contracts are self-executing algorithms written in code and stored on a blockchain. They automatically execute when predefined conditions are met. Once conditions are agreed upon, the contract executes automatically and cannot be stopped or modified. The concept was originally defined in 1994 by computer scientist Nick Szabo, but gained practical application only with the emergence of full blockchain networks.

This section provides comprehensive coverage of distributed ledger technology and smart contracts. A distributed ledger is a consensus of replicated, shared, synchronized digital data across multiple locations without centralized administration, supporting any asset type from physical property to intangible assets like votes and health data. Two main types exist: public ledgers (like Bitcoin) accessible to anyone, and permissioned ledgers (like Ripple) with controlled validators. Smart contracts are self-executing code stored on the blockchain encoding contractual agreements that execute automatically without discretionary enforcement by third parties. Once launched, contracts operate autonomously without further contact between parties. The section explains how these technologies enable replacing multiplicity of private databases with one shared trusted database, strengthening collaboration between organizations and individuals peer-to-peer without dependency on third parties.

A smart contract is a self-executing contract where the terms of an agreement are written directly into lines of code. This code exists on the blockchain, a decentralized secure ledger. Once the conditions in this contract are met, the contract automatically executes its agreed actions without needing a third party like a bank or lawyer to verify or process the terms. It functions as a digital if-then statement—for example, releasing a security deposit when certain conditions like leaving an apartment in good shape are verified.

A smart contract is a self-executing digital agreement with the contract rules written directly into immutable computer code. It runs automatically across a decentralized blockchain ledger once specific predetermined agreement criteria are met. By removing human intermediaries, it slashes transactional costs and completely eliminates third-party counterparty risk. This technology enables automated execution of agreements without lawyers or banks involved.

This segment covers the foundational architecture of a stack-based virtual machine. Key topics include: the purpose of virtual machines for understanding computer systems, stack machine design principles, C++ class structure with private registers (program counter, stack pointer, type/data registers, running status) and public methods, type definitions for 32-bit integers, and the instruction encoding format using 32-bit words with 2-bit headers for instruction classification (positive integers, primitives, negative integers). The video explains how helper functions extract instruction types and data, establishing the framework for CPU execution.

A virtual machine is a simulated computer that executes bytecode instructions through a fetch-decode-execute cycle, using a stack-based architecture where all operations occur on a stack, with the interpreter managing memory, registers (instruction pointer, stack pointer, frame pointer), and function calls through activation records to enable recursion and maintain state across nested function invocations.

Virtual machines are software execution environments that run pseudo-assembler instructions rather than native processor code. They are platform-independent and can execute the same bytecode on different operating systems. Stack-based virtual machines use an abstract, potentially infinite stack for computation instead of physical CPU registers. Values are pushed onto the stack and popped off for operations. This approach provides seemingly unlimited storage space and simplifies the implementation of complex expressions. The stack data structure follows Last-In-First-Out (LIFO) principles, where items are added and removed from the top.

Any VM requires three core components: ISA (defines available instructions), memory model (defines how memory is organized and accessed), and machine model (defines execution semantics—register-based or stack-based). Register-based machines store operands in dedicated registers, while stack-based machines push operands onto a stack and perform operations by popping values. Modern processors are register-based, while many VMs (including JVM) use stack-based models for portability and simpler compilation. VMs execute bytecode through interpretation (slowest), Just-In-Time compilation (compiling frequently-used code during execution), and Ahead-Of-Time compilation (pre-compiling before execution). The JVM uses an object-based memory model where objects are allocated on the heap and accessed through references, with each thread having its own stack containing stack frames for local variables and operand stacks for intermediate computations.

A virtual machine is a software emulation of a computer system that executes programs written in a specific virtual instruction set. The video covers the three main components: theory, compilation of source code to machine code, and execution. Source code exists in two variations: high-level (like Java) and low-level (like assembly). The compilation process involves translating high-level code to low-level code, then compiling to bytecode for the virtual machine. Virtual machines can be stack-based or register-based, with stack-based being simpler to implement but potentially slower. The performance trade-off between interpretation and compilation is explained, with virtual machines providing a middle ground. The implementation requires two main functions: readvm_source for compiling source code to bytecode, and readvm_exec for executing the compiled bytecode. A stack data structure requires a type system supporting int, float, and string types, a buffer for storing values, a size indicator, and an index pointer. Key operations include push, pop, get, and free. The virtual machine instruction set includes: push, pop, add, subtract, multiply, divide, jump, conditional jumps, store, load, call, return, exit, label, and comment. Each instruction has a specific opcode and may have arguments.

Blockchains update user balances using two fundamentally different bookkeeping models: the UTXO model (used by Bitcoin) treats transactions like physical cash, where each transaction creates new unspent transaction outputs that can be spent as inputs, offering better privacy and parallel processing but greater complexity; while the account-based model (used by Ethereum) works like traditional bank accounts, directly debiting and crediting balances, making it simpler for smart contracts but potentially compromising privacy and limiting throughput.

Bitcoin uses the Unspent Transaction Output (UTXO) model where each transaction creates new coins from spent outputs. Ethereum uses an account-based model where accounts hold balances directly. In Ethereum, each account stores a single balance value, regardless of transaction history. This makes Ethereum more efficient for frequent transactions since account updates are constant-size operations, whereas Bitcoin's UTXO model grows linearly with transaction count. The account model resembles traditional banking databases, simplifying state management while increasing storage efficiency.

This section compares two fundamental blockchain transaction models. Ethereum uses an account-based model where transactions are procedural function calls that execute code with parameters, processing sequentially due to shared state dependencies. Cardano uses the UTXO (Unspent Transaction Output) model where funds are tracked as distinct outputs, enabling parallel validation when transactions don't share inputs. The UTXO model behaves like cash and change, explicitly defining transaction results. Key advantages include parallel validation capability and natural sharding potential. Trade-offs include more complex balance calculation and UTXO selection algorithms. The eUTXO model extends UTXO to support smart contracts while preserving these core properties.

This segment explores the fundamental architectural differences between Bitcoin and other cryptocurrencies. The presenter explains that Bitcoin uses the UTXO model where each transaction creates new coins with addresses, while account-based systems like Ethereum use a single address for all assets. This architectural difference has significant privacy implications: account-based systems reveal entire portfolio balances with every transaction, making them more dangerous for privacy. The segment also covers privacy coin limitations, explaining that even Monero provides 'extremely difficult to trace' rather than '100% untraceable' anonymity, and introduces the anonymity set concept where users hide among fewer people.

In the UTXO model (used by Bitcoin), transactions operate on individual coins rather than account balances. When you receive money, you're destroying some of your coins and creating new ones—one going to the recipient and one returning to your wallet. You must spend a coin completely, and if you don't want to send all of it, you split the coin into two parts. In contrast, the account-based model (used by Ethereum) uses accounts that can grow or shrink in size, similar to a bank account balance.