Explain the main principles of memory management in software systems

The main principles of memory management in software systems include:

1. Memory allocation — the process of reserving a memory area for storing data or code.
2. Memory freeing — returning previously allocated memory to the system for reuse.
3. Object lifetime management — determining when an object is no longer needed and its memory can be freed.
4. Garbage Collection — an automatic mechanism for finding and freeing unused objects.
5. Reference Counting — a method of managing object lifetime where an object is deleted when the number of references to it becomes zero.

In iOS, for example, automatic memory management is used with ARC (Automatic Reference Counting), which automatically increases and decreases the reference count of objects, freeing them when they are no longer needed.

Example with ARC:

class Person {
    var name: String
    init(name: String) {
        self.name = name
    }
}

var person1: Person? = Person(name: "Alice")
var person2 = person1 // reference count increases
person1 = nil // reference count decreases
person2 = nil // object is freed

Proper memory management helps prevent leaks and application crashes.