View and Download Casio Fx-115ES user manual online. Casio fx-115ES fx-991ES Calculator User's Guide. Fx-115ES Calculator pdf manual download. Also for: Fx-991es, Fx-115es-s-ih. Fx-115ES PLUS fx-991ES PLUS C. User's Guide. CASIO Worldwide Education Website CASIO EDUCATIONAL FORUM. Fx-991ES basically is a full functions model in the ES serie. In previous models the fx-115MS had not constant table, which was present in the fx-991MS. Concerning user manual and CASIO web site, fx-115ES and fx-991ES both same models. But I preffer to buy the fx-991ES instead of fx-115ES. May be, the fx-115ES will contain some undocumended.