I'm a c++ begginer who knows basics in c++, data structures and algorithms.

I want to develop a super mario game in sdl2 and openAl.

But I know nothing about these things. Could anyone guide me like how and where to start? What are the things that I should know?

Welcome.

Just start, with practice comes confidence.

Maybe you can find a C++/SDL 2D game tutorial or so that fits you, read the documentation, but nobody can take the burden of practice from you. When you say “i know nothing” it is probably too overwhelming right now to enumerate the skills you'll need or not. So, go ahead, if you get stuck there will be help.

Take a look at other's code, play with an engine if you like, program things, …

Lazy foo has nice SDL2 tutorials: http://lazyfoo.net/tutorials/SDL/​

(note: the site also has (or had) SDL1 tutorials , I don't know if they have been removed, but they can be hard to distinguish from SDL2)

develop a super mario game in sdl2 and openAl

Using names owned by a company is not a good idea, they will defend their name. It is fine to make a game of the same type, but you cannot name it “mario” or any other known name. Instead invent your own name, that makes it also possible to give the game your own twist.

Thanks for your answers.