PCC is a small, simple, fast and understandable C99 compiler based on the original Portable C Compiler by S. C. Johnson, written in the late 1970s. Focus on being able to compile and run on a PDP11, even if it may not happen in reality, keeps it lean; abstinence from over-complicated algorithms leads to quick reliable code generation. Even though much of the compiler has been rewritten, some of the basics still remain.