Hi, welcome to the programming world.
You're an optimist, and that is OK. However you will need a lot of knowledge: language, methodology, application domain, ...
I doubt assembly (any CPU) nowadays is a good choice for your first coding steps; it requires you to be utmost meticulous, and that you are not (your description, just three sentences, contains a big inconsistency). On the slightest mistake, assembly code just crashes.
A higher-level language, such as C or Java or C#, would be a much better choice, as there are far less minute details you must get right all the time; yes, these languages my be more complex, but then you don't need to know all of it to get started, and the compilers will try and keep you on track towards code that actually runs. Be warned, no compiler or assembler can ensure your code does what you intended it to do.
I would recommend a short stay in C, and then a switch to either Java or C#, both of which will force object orientation on you. You shouldn't start coding on your own, either get a course, or study a book. I recommend you own and study a book on the language, preferably a wooden tree book, so you can easily browse it, make anotations, etc.
Whatever language you choose, a calculator is not something you will create successfully in the first months of your learning process. Have you any idea how to create a user interface, with a numeric display, a bunch of buttons, etc ?
Maybe it would be a good idea to read some of the articles CodeProject holds, e.g. Maya Calender Calculator