The stack

As we saw in the preceding sections, the stack together with the CPU registers define a task. As mentioned earlier, this stack consists of stack frames, each of which defines the (local) variables, parameters, data, and instructions for that particular instance of task execution. Of note is that although the stack and stack frames are primarily a software concept, it is an essential feature of any modern OS, with hardware support in many CPU instruction sets. Graphically, it can be be visualized like the following:

The SP (ESP on x86) points to the top of the stack, with another pointer (Extended Base Pointer (EBP) for x86). Each frame contains a reference to the preceding frame (caller return address), as set by the OS.

When using a debugger with one's C++ application, this is basically what one sees when requesting the backtrack--the individual frames of the stack showing the initial stack frame leading up until the current frame. Here, one can examine each individual frame's details.