The Saturn Homebrew Repository for Example Code, or SHREC, strives to provide working examples of code necessary to create homebrew games for the Sega Saturn using tools currently available for free online. Here you can find the necessary and sufficient code required to create building blocks for homebrew games on the SEGA Saturn.
The SEGA Basic Library is the fundamental official codebase for programmming on Saturn. It has everything you need for making a game, and nothing more. (Hello World code example coming soon.)
The SEGA Graphics Library is an expanded library on top of SBL that is/was used by the vast majority of Saturn developers.
Begin here if you're just getting starting learning Saturn homebrew programming. Learn how to make games using Jo Engine.