An assembly language: it really doesn't matter which one. It can even be an 8-bit CPU like a Z80, or 6502. In fact, maybe even best would be an 8-bit CPU. C.

An assembly language: it really doesn't matter which one. It can even be an 8-bit CPU like a Z80, or 6502. In fact, maybe even best would be an 8-bit CPU. C. It's the foundation of today's software: operating systems, databases, embedded systems -- all mostly written, even in 2021, in C. Lisp. Doesn't really matter which one. It's just a different way of approaching problems. Python. It's hard to beat for translating an idea into running code. JavaScript. Ok, it might not be the "best" language, but it is deployed to literally billions of people and you should know how to put your software in front of them. After these, you can pick up other things as required. C++, C#, Java, Rust, Go, Swift, whatever. Try something new every few years.