Smart Contracts
Solidity is the most common language that is used to write Smart Contracts
Solidity code is converted into bytecode that can be executed by the EVM
GitHub - Faucet.sol
To register a contract a transaction with destination address of all zeros is used
Contract creation transactions don’t need to have ether
Gas fee equivalent to the size of the contract will be charged
Contract accounts do not contain any private keys
The contract creator does not get any special privilege over the contract
Contracts only run when they are called using a transaction
Contracts cannot be executed in parallel - Ethereum single-threaded machine
Contracts are atomic. If any error occurs during the execution of the contract the state changes are rolled back
Contracts can be deleted using the SELFDESTRUCT command
Ethereum ABI
An ABI (Application Binary Interface) is an interface between two program modules
The two programs is often the OS and user program
Defines how data structures and functions can be accessed in machine code
Ethereum ABI to define the contract calls for EVM and read data from transaction
Defines which functions can be called and what arguments it can accept
A contracts ABI is defined as a JSON array
Solidity
Global Objects: blocks, msg and tx
The msg object is responsible for contract execution
The constructor function is run when the contract creation transaction is executed
A contract can be deleted if it contains a destructor
When a transaction completes execution it created an transaction log
Events are used to represent the transaction logs in Solidity
GitHub - Faucet8.sol