Hmmm....Flame not easy to put everything up here
Try http://www.planetsourcecode.com and search for your code requirements, eg enter Calculator to the search criteria.
You should get numerous examples of what you want, which can be downloaded.:):):):)
There doesn't seem to be an easy way of posting code up here,so any in depth stuff is going to take a heck of a lot of typing.
FYI
If you need code, start your project, get something happening in it, and then ask specific questions. You are more likely to get responses. Just a thought:):)