After a long search for the scientific calculator, 991ES from Casio, today I bought one for 700INR. I enquired for this model in many shops, even abroad, but got the reply that its out off stock. At last, a book shop at Valanchery helped me in getting one. The calculator has got more than 400 functions, 40 scientific and is much helpful for engineering students. Unlike from other models, it has got a Natural Textbook Display and easy to use interface and is slim. It come along with a detailed instruction manual about all its functions.