PYTHIA version 7-0.0 - a proof-of-concept version

This document describes the first proof-of-concept version of the PYTHIA7 p rogram. PYTHIA7 is a complete re-write of the PYTHIA program in C++. It is mainly i ntended to be a replacement for the 'Lund' family of event generators, but is also a framework with a structure suitable for implementing any event ge nerator model. In this document, the structure of the program is presented both from the u ser and the developer point of view. It is not intended to be a complete ma nual, but together with the documentation provided in the distribution, it should be sufficient to start working with the pro,sram. (C) 2001 Elsevier Science B.V. All rights reserved.