Computer Science might be the most important field of study today, as it impacts our lives in so many different ways.
The basics of programming are enough to get into computer science, and beyond that everything you need to know will be application-specific.
There are hundreds of not thousands of programming languages out there, but I have chosen to focus on Python and Java.
Python is the most popular language currently and is used in Machine Learning and Data Science, whereas Java is more old-school, and it will give you more freedom to do more “Low Level” programming closer to the hardware.
Therefore this page is divided into Java and Python:

Python:

Java: