Changes

You'll need a compiler. Apple provides two ways to install one: "Command Line Tools" installs just the command-line build environment and puts most of the header files in <ttcode>/usr/include</ttcode>. Simply trying to run a program that requires it like <tt>gcc</tt> or <tt>git</tt> should produce a dialog box offering to install them, but if that doesn't work you can run <ttcode>sudo xcode-select --install</ttcode>. Apple also has a full-featured integrated development environment called Xcode. It's available for free from the Apple App Store.

If you try to download Xcode, Apple will probably offer you the latest version of Xcode, irrespective of whether it runs on the version of macOS/Mac OS X you are using (Apple probably expects you to upgrade everything to the very latest). That probably doesn't matter, since we don't need to run the app, we just need the compilers and software development kit.