Answer 1

the memory of stack is fixed and predefined. when you actually know exact amount of memory that'll needed in compilation time, you will use stack. other hand the memory of heap is virtual. when you does not know the exact amount of memory that will needed in run time, you will use heap. so heap is a virtualization of memory.so it can be huge or small amount. for these memory alocation flexibility, it is called dynamic. other hand stack is fixed so it is static.