On platforms that support markdown, you can usually create the code formatting by using four (4) spaces at the beginning of every line. Fenced code blocks do not render properly on mobile or new Reddit, but likely will on platforms that have a better markdown renderer. If you are using a platform that does not support markdown, you can use the html tags <pre> and <code> to create the code formatting.

It is not usually necessary to mention the programming language or source of the code, but if it is relevant within the context of the specific post, it should be included in a description before the code.