Arduino Calculator using LCD + PS/2 Keyboard

Hi! I'm making an arduino calculator using arduino UNO, LCD 16X2 and a PS/2 Keyboard. I have found this code and I have made the circuit and it works very good!!! I just want to add something new. I want to give as input from the keyboard, real numbers (for example: 2.3 or 5.53 etc.). Can someone modify the code that will work this way? You would really help me a lot. Thank you!

The code is on the attachments.

KWDIKAS_PTYXIAKIS_2_.ino (20.7 KB)

Can someone modify the code that will work this way?

Maybe after YOU rewrite it to NOT use Strings. NOTHING that the code is doing needs Strings.

The problem is that i'm amateur on arduino and I don't know how to mofify it right. That's ok. I believed someone could help me. Can I ask something else? When I'm doing the "2^3" for example it gives "8" as answer which is right. But when I'm giving "2^0" or "5^0" etc, it gives me as answer the number who is base. It has to give me "1" as answer. Do you know where is the problem on the code?

It is calculated here. It should not be too hard to modify.

String cheak_square(String n){       //create function cheak_square receive paramiter from number ex. 2^3
…
       if(Square_index==0){                 //index square equal 0
          Number = n;
       }