PCN is a system for developing and executing parallel programs. It comprises a high-level programming language, a set of tools for developing and debugging programs in this language, and interfaces to Fortran and C that allow the reuse of existing code in multilingual parallel programs. Programs developed using PCN are portable across many different workstations, networks, and parallel computers. This document provides all the information required to develop parallel programs with the PCN programming system. It includes both tutorial and reference material. It also presents the basic concepts that underlie PCN, particularly where these are likely to be unfamiliar to the reader, and provides pointers to other documentation on the PCN language, programming techniques, and tools. PCN is in the public domain. The latest version of both the software and this manual can be obtained by anonymous FTP from Argonne National Laboratory at info.mcs.anl.gov.