This is a infinite digit adder. The cursor and delete button modifications have also been made. Sum of an integers returns an integer. There are 2 types of addition- One which is limited to 1.7*10^308(around 308 digits). Other is Big= which has no limit whatsoever.
Other operators are also incorporated, they are limited to 308 digits.
For using BIG=, just use normal + and after that press BIG= instead of =.