Push operation allows users to insert elements in stack. If stack is filled completely and trying to perform push operation stack overflow can happen.

Elements in stack are removed using pop operation. Pop operation removes the top most element in the stack i.e. last entered element.

Underflow occurs when the user performs a pop operation on an empty stack. Overflow occurs when the stack is full and the user performs a push operation. Garbage Collection is used to recover the memory occupied by objects that are no longer used.

The stack is filled with 5 elements and pushing one more element causes a stack overflow. This results in overwriting memory, code and loss of unsaved work on the computer.

In stack data structure, elements are added one by one using push operation. Stack follows LIFO Principle i.e. Last In First Out(LIFO).