For your purposes I would recommend C. It's a very small language with very little abstraction, so it forces you to really understand pointers and memory layout

For your purposes I would recommend C. It's a very small language with very little abstraction, so it forces you to really understand pointers and memory layout. Rust is more complicated than C and it tends to insulate you from the low-level details. The way it combines low-level control with high-level abstractions is really interesting, but from an educational point of view I think you'd get more out of it after you understand C pretty well. C++ is a giant, sprawling mess. It can be very useful but I'm not sure what it will teach you other than how not to design a language. :)