how does a program runs in memory and the way memory is handled by Operating system

Question

I am not clear with memory management when a process is in execution during run time

Here is a diagram

Answer 1

Part 1. The Stack ...

A function can call a function, which might call another function. Any variables allocated end up on the stack through each iteration. And de-allocated as each function exits, hence "stack". You might consider Wikipedia for this stuff ... http://en.wikipedia.org/wiki/Stack_%28abstract_data_type%29