The cat will tell you the instructions. Just like a normal calculator. You can do a 2-number operation or getting a variable of one number (1-number operation).
List of 1-number operations: abs, floor, ceiling, sqrt, sin, cos, asin, acos, atan, ln, log, e, 10, round. (Scratch - Operators: () of (), and round ()) don't bug da cat please don't the cat