Explain the principle of Copy-on-Write and how it works in memory management systems.

Copy-on-Write (COW) is a memory management optimization where multiple processes or variables initially share the same copy of data. Actual copying occurs only when one of the parties attempts to modify the data.

In memory management systems, it works as follows:

• When creating a copy of an object or memory page, a reference to the same data block is created.
• All parties can read the data without issues, as it is not changed.
• When a write (modification) is attempted, a 'lazy' copying occurs — a separate copy of the data is created for the modifying party.
• After this, changes do not affect other copies.

This allows saving memory and increasing performance by avoiding unnecessary copying.

In Go, for example, a similar principle can be observed when working with certain data structures and when passing slices, where copying occurs only when necessary.