UpperCamelCase : Class, Structure, Enumeration, Extension, Protocol
lowerCamelCase: Variable, Constant, Function, Property, Parameter
Number Literals: 1, 1.2, 1.23e4,0xAp2, 1._000_000, 0b010011 등
사이에 공백 불가.
Number Types
: Interger Types(Int8,Int16,Int32,Int64), Floating Point Types, Double Types
음수가 필요없다면 앞에 U를 붙여 UInt를 사용.