Does anyone know how to write a program that does simple arithmetic operations? Any tips would be appreciated!?

I have to write one for cl and I am having a lot of syntax problems, and this is my first fortran project. It has to be fortran...I know its outdated but it is whats required. Obviously I need to do this project on my own but if anyone could get me started or show me a program that simply just adds that would be helpful. (mine has to add subtract multiply and divide)