What are the differences between data types in terms of their semantics: values and references?

Data types by semantics are divided into value types and reference types.

• Value types store data directly. When assigned or passed to a function, the value itself is copied. In iOS (Swift), examples include Int, Double, Bool, and structures (struct).

• Reference types store a reference to a memory area where the data resides. When assigned, the reference is copied, not the data. Changes through one reference are visible through others. In Swift, these are classes (class) and objects.

Example:

struct Point { var x: Int; var y: Int }
class Person { var name: String
  init(name: String) { self.name = name } }

var p1 = Point(x: 1, y: 2)
var p2 = p1
p2.x = 10
print(p1.x) // 1 — copy did not change

var person1 = Person(name: "Ivan")
var person2 = person1
person2.name = "Peter"
print(person1.name) // "Peter" — reference to the same object

Understanding the difference is important for memory management and object behavior in an application.