How do you call the discipline which consist of making the right choice of language/paradigm/class diagrams?

How do you call the discipline which consist of making the right choice of
language/paradigm/class diagrams?

As a physicist, I've learnt programming on my own. But I would like to
know the name of the discipline (like algorithmics is the discipline of
designing algorithms) which consists of :
making the right choice of language/paradigm
designing a class diagram
organizing the different parts of a code and how they will interact
between each other