This describes the Object Oriented Pre-Compiler, OOPC , a language and a run-time library for producing C programs that operate by the run-time conventions of Smalltalk 80 2 in a UNIX 3 environment. These languages offer Object Oriented Programming in which data, and the programs which may access it, are designed, built and maintained as inseparable units called objects .The precompiler is backed by a library which supports Smalltalk 80's interpretation of messaging; binding of a message to its target routine is done at run time. The library also contains a growing number of primitive class definitions, such as an Object class whose capabilities are inherited by every object in the system. The library provides many, but not all, capabilities of Smalltalk. An added capability is object save/restore , which allows any object to convert itself and all sub-objects into linear form for storage on disk. Important missing features are automatic memory management and Smalltalk's impressive collection of classes to support a graphical human interface.