Copy-on-write

Copy-on-write (COW), also called implicit sharing^[1] or shadowing,^[2] is a resource-management technique^[3] used in programming to manage shared data efficiently. Instead of copying data right away when multiple programs use it, the same data is shared between programs until one tries to modify it. If no changes are made, no private copy is created, saving resources.^[3] A copy is only made when needed, ensuring each program has its own version when modifications occur. This technique is commonly applied to memory, files, and data structures.