Copy-on-Write

Suppose we have 2 processes, Process 1 (the parent) and Process 2 (the child of Process 1). When one of the pages of Process 1 changes, only then we create a new page copy. Otherwise, both processes will point to the same pages.

Before process 1 modifies page C. Taken from Bell, John T. "Virtual Memory." University of Illinois, Chicago.

After process 1 modifies page C. Taken from Bell, John T. "Virtual Memory." University of Illinois, Chicago.