>when i design a programm for processing science data , i draw a curve use these data on a form ,
> now i will print it into a .bmp file for save,final i will save it into general field.
>
>but i don't know how to save graph which draw in form
>into a .bmp file.
>could you tell me?

When come time to deal with graph, you may want to consider using an OCX for graphing, as Edward told you, which will let you programmaticaly do the save, the print, etc. or let the user have access to these features.

I personally have used ProEssential but there are many other good OCXs as well for doing this job.