Call stack

A call stack stores active procedure calls and the information needed to resume each caller, such as its return location and local variables. A call adds a frame; returning removes that frame and resumes the previous call. When depth-first search uses recursion, a frame also records where its adjacency list scan paused. The active frames describe a graph path from the starting vertex to the current vertex; finished calls have left the call stack, although their vertices remain marked as discovered.