Which programming languages are recommended for making an OS and which are recommended for making games

Answer 1

For OS you can search for the various OS and their programming languages on Google.com.

With the game language C++ and C# are the common ones.

This question has being asked several times on Sololearn Q/A discussions, you can try searching.

Good luck in it

Answer 2

C# not primarily as it is compiled to an IL (intermediate language) executed by an RE (runtime environment) that uses OS (operating system) functionality).

For Games you'll propably need more than one language. OpenGL/OpenCL/CUDA or a Framework (like Unity) for 2D/3D purposes and whatever you want for the rest ... depends, as usual (in target plattform, project scope, ...).