Dear friends, it my first post. As I see, this form is helpful for the pleople who needs help on many topics. Before talking about my problem, I would like to say I can code some programs in Visusal Basic 6.0, Matlab and Maple. I have coded a program in Maple, but I have just learned that Mathematica draws much more better in 3D when compared to Maple. So , I need to code the same program in Mathematica. May I please get some information about the following topics: How to write a 'for next' loop? How to load values in to a double sequence (or a matrix, i.e. x(m,n) for m=1,2,...,20 and n=1,2,...,10)? How to plot a double sequence on 3D (with the form [m,n,x(m,n)])? Thanks. Note. If it could help I can also write the Maple codes.