SGDK is an open and free development kit for the Sega Megadrive.
It contains a development library (sources included) to make software on Sega Megadrive / Genesis system and a GCC compiler toolchains (Windows system only).
Note that some tools requires Java.
You can find the library doxygen documentation in the 'doc' directory: doc/html/files.html
You can find basics tutorials about how install and use SGDK on this page:
Unix/Linux users should give a try to the Gendev project from Kubilis:
It allows to quickly setup SGDK on a Unix environment.
And now MACOS users also have access to SGDK with Gendev for MacOS from Sonic3D :
SGDK and affiliated tools are distribued under the MIT license (see license.txt file)
If you want to donate to support SGDK development: