LCC is simple to understand and well-documented: its design is described in A Retargetable C Compiler: Design and Implementation (ISBN 0-8053-1670-1).
The Lcc-win32 or LccWin32 system is a full featured C Development Environment for the Microsoft Windows operating system, written by Jacob Navia. He continued the work of Hanson and Fraser, who wrote the original LCC compiler.
Under development - can currently successfully compile itself, the IDE (wedit64) and around 550 test files. lcc-win64 will also feature more advanced code optimizations.
LCC is free for personal use and may be redistributed with attribution. LCC may not be sold for profit, but it may be included with other software that is sold for profit.