Python

It's an amazing scripting language, and my goto for writing automation scripts.

It's the most lenient of the 3 with dynamic typing and managed memory. It'll let you learn the basics of reading / writing / running code as well as basic control flow and logic

C is also great to learn, as it teaches you how computers work at a fundamental level, but it's more stuff to learn up front, and can lead to some very difficult to fix bugs

Java is good as an "application" language. Being memory managed like Python, but statically typed like C. Static typing makes it easier to manage larger code bases

Mac is very similar to Linux in that it comes with bash (these days zsh) and a lot of the command line tools you’d expect on Linux, including gcc and python3 installed by default. You’ll want them to have a decent text editor with code coloring. Sublime is what I was taught to use in university.

Windows is more difficult. The command line is very different (it inherits from DOS instead of Unix like both Mac and Linux). It doesn’t come with Python pre-installed. I’ve generally installed git-bash when working on Windows. There are some Python libraries that work fine on both Mac and Linux but have issues on Windows.

You could look into VSCode which is a decent IDE that works on all platforms. Of course, an IDE can be a bit of an information overload for a beginner, especially something like VSCode that’s constantly pushing AI features and plug-ins.

Absolutely do not use Python. It’s a nightmare to install on random computers and the majority of your time spent will be trying to get it working on everyone’s computer (that was my job at one point). As far as I remember, there isn’t a “good” C compiler that comes on windows and the one on Mac is missing some stuff.

I’d go with Ruby, it’s dead simple to install on every OS, easy to teach and learn, and doesn’t work differently across OSes. There’s an installer for it for windows and it comes installed by default on Mac (or it did? Maybe they stopped that).