This is the execution of the standard sum algorithm. You write the numbers and the program execute the sum like a human do. Obs: I'm using the new blocks to organize the code and I'm using Test Driven Development TDD with an especific procedure that detect the output and tell if it's true or false. Obs2: To make a simulation of TDD you can put an error in the app pressing the space during the execution. Then you'll see the application detecting automaticaly the error. TDD is very important technique to develop code with good quality, TDD let you in the control of the code, Then you can modify the code without fear. I suggest you looking for more about TDD.