Explain the Copy-on-write principle and how it is used to optimize memory management.

Copy-on-write (COW) is an optimization technique for memory management, where data copying is deferred until the data is modified.

Working principle:

• When copying an object, a new copy of the data is not created; only a reference to the existing data is made.
• As long as the data is not changed, all copies share the same memory area.
• When an attempt is made to modify the data, a real copy occurs ("write") so that the changes do not affect other copies.

This allows saving memory and reducing overhead for copying large data structures.

An example of COW usage can be found in memory management systems, file systems (e.g., Btrfs), as well as in programming languages and libraries where objects are copied lazily.

Pseudo-code example:

class CowList(private var data: List<Int>) {
    private var isShared = true

    fun modify(index: Int, value: Int) {
        if (isShared) {
            data = data.toMutableList() // copy on write
            isShared = false
        }
        (data as MutableList)[index] = value
    }

    fun getData() = data
}

Thus, COW allows efficient memory usage by avoiding unnecessary copies until the data is actually modified.