The calculator evaluates an expression in postfix and give its output Algorithm: --> Create a stack to store oprerands(Values)
--> Scan the given expression and do the following for every scanned element:
->If the element is a number, push it to the stack
->If the element is an operator, pop two operands from the stack evalaute the two popped elements with the current operator and push the result back to the stack.
--> When the expression is ended, the top element in the stack is the answer (pop())