One thing I will like to say about my calculator is that " I am very possessive about my calci". Itz only my property..I don’t allow anybody to use it.
Anyways 991 MS is all in one calci. It has lots of function, , today also I don’t know how to use those functions.
I am using this calci when I was in 1st year of engineering. My mom purchased it for me on dec 2002 (ie. frm 6 years I am using it) and itz still working properly (touch-wood).
It has two-way power --one battery and other solar. It is very slick and easy to handle and also durable. It has basic mathematical functions and best feature of it is that it has higher maths functions too.. Like vector, matrix, complex no., differentiation, integration and many more. It makes calculation very fast and easy. It has wonderful memory to ease calculations. It saves lots of calculation time.
I still dont know how to make use of it with the full extend. As it has lots of functions, some time itz not easy to use, , but casio provides a booklet ie. manual which contains all of its features and help to use those features. The display screen is also good. When I purchased my calcii it was very costly ie. Rs.800. But now a days itz cost has been reduced. Its a affordable and reliable calci.