Summary: The computation errors come out in the computers (uses oating point numbers) during calculations of mathematical problems. Therefore, the floating point numbers affect the results directly. In [A. O. Çıbıkdiken and K. Aydın, Comput. Math. Appl. 67, No. 5, 1186–1194 (2014; Zbl 1350.65141); Konuralp J. Math. 4, No. 1, 23–32 (2016; Zbl 1355.39024)], the computation of fundamental matrix analyzed for the stability of periodic linear difference equation systems. These works used Wilkinson Model and Godunov Model. In this study, the computation of fundamental matrix has been studied on extended floating point numbers. The results have been applied to Schur stability of the system of linear difference equations with periodic coefficients. Furthermore, the effect of floating point arithmetics has been showed on numerical examples.