These notes help to aid my short term memory.
- a Contract is a class
- Hello World
// SPDX-License-Identifier: MIT
// compiler version must be greater than or equal to 0.8.17 and less than 0.9.0
pragma solidity ^0.8.17;
contract HelloWorld {
string public greet = "Hello World!";
}- an Address is
- In Ethereum and Solidity, an address if of 20 byte value size (160 bits or 40 hex characters). It corresponds to the last 20 bytes of the Keccak-256 hash of the public key. An address is always pre-fixed with 0x as it is represented in hexadecimal format (base 16 notation) (defined explicitly).
- the purpose of an Address
- An address value type is specifically designed to hold up to 20B, or 160 bits, which is the size of an Ethereum address. Solidity actually offers two address value types: address and address payable . The difference between the two is that address payable can send and transfer Ether.
- Data storage and representation in the EVM
- The address and address payable types both store a 160-bit Ethereum address. The concept of payable and non-payable addresses only exists in the Solidity type system at compile-time. The difference between payable and non-payable addresses is gone in the compiled contract code.
-
https://blog.logrocket.com/ultimate-guide-data-types-solidity/#addresses
- An address value type is specifically designed to hold up to 20B, or 160 bits, which is the size of an Ethereum address. Solidity actually offers two address value types: address and address payable. The difference between the two is that address payable can send and transfer Ether. We can use an address to acquire a balance using the .balance method and to transfer a balance using the .transfer method.
// example of an address value type in solidity
Contract SampleAddress }
address public myAddress =
0xb794f5ea0ba39494ce839613fffba74279579268;
}- https://ethereum.org/en/developers/docs/evm/
- The EVM’s physical instantiation can’t be described in the same way that one might point to a cloud or an ocean wave, but it does exist as one single entity maintained by thousands of connected computers running an Ethereum client.
- The Ethereum protocol itself exists solely for the purpose of keeping the continuous, uninterrupted, and immutable operation of this special state machine. It's the environment in which all Ethereum accounts and smart contracts live. At any given block in the chain, Ethereum has one and only one 'canonical' state, and the EVM is what defines the rules for computing a new valid state from block to block.