APCS has a guide that helps you use VirtualBox to install an environment on your computer that you can use to write and run the programs shown here in the APCS section. You can also use wsl on windows or the native shell on a mac. But since it provides such a wonderful standard environment you may wish to go with the APCS guide anyways.
You can find these guides online, including a PDF guide and direct links to the software you need here: https://apcs.csie.ntnu.edu.tw/index.php/info/environment/
Answers are programs input using (ex. vim) and written in C, C++, Java or Python.
You can learn the languages here: https://apcs.csie.ntnu.edu.tw/index.php/questionstypes/websites/
Programs must compile and run using the APCS specified commands below:
I suggest you start with vim. This is because it will always be available in this environment. To start, use (esc) to get into command mode and then experiment with the a and i commands (to insert and append). When you are done type :w from the command mode and then :q to quit. For more information on vim check out our vim guide.