Graphical Loop Invariant Programming in CS1

This paper introduces the use of Graphical Loop Invariant as a programming methodology in a CS1 course, in which the Loop Invariant is determined prior to writing the code and is meant as a help to find the loop instructions. This paper also introduces two learning tools: GLI, an application helping students to draw Loop Invariant and CAFÉ, an on-line platform designed to assess and deliver automatic feedback and feedforward information to students, in particular on their Loop Invariants and the pieces of code based upon them. The paper reports preliminary evaluation on Café usage.