Contract in Solidity are like classes in OOP programming
Contracts can hold:
Data and functions
Contract execution is paid with gas (Bus Analogy)
Contract is compiled by the solidity compiler
Mapping in Solidity
Application Binary Interface (ABI)
Describes the contract’s interface
Public methods
Inputs
Return values
Events
Gas
Gas is the internal unit for keeping track of execution costs Ethereum
Gas cost measures the consumed computational resources Ethereum
Each CPU instruction in EVM costs gas
Each persistent storage write also costs gas
Ex. Writing 32 bytes into a contract memory costs 80000 gas
Gas price is how much someone is willing to pay per unit of Gas Cost Ethereum
Gas cost vs Gas price
If you are driving to California from Arizona, you would always have the same gas cost (how many miles), however you would probably pay a different “gas price” for this depending on the supply/demand etc etc
Gas price is how much someone is willing to pay per unit of Gas Cost Ethereum