The main course work of 6.035 is the design and implementation of a compiler. In each segment of the course, a part of the compiler will be constructed. The five segments are: the scanner and parser, semantic checker, code generator, data-flow optimizer and instruction optimizer. The five assignments are all group projects. Students may choose between two versions of the compiler project: an 18-unit version (more time consuming) and a 12-unit version. The 12-unit version of the project is intended to provide a hands-on experience of building a simple yet complete compiler. The 18-unit version of the project is intended to also illustrate some of the real world problems that arise in building industrial-strength compilers. The project documents in this section refer to Athena, which is MIT's UNIX®-based computing environment.