Structure of a Contract

Contracts in Solidity are similar to classes in object-oriented languages. Each contract can contain declarations of state variables, functions, function modifiers, events, structs types and enum types. Furthermore, contracts can inherit from other contracts.

• State variables are values which are permanently stored in contract storage.
• Functions are the executable units of code within a contract.
• Function modifiers can be used to amend the semantics of functions in a declarative way.
• Events are convenience interfaces with the EVM logging facilities.
• Structs are custom defined types that can group several variables.
• Enums can be used to create custom types with a finite set of values.