This document is a description of the computer code OSFIC. The development of the code was sponsored by the Swedish Nuclear Power Inspectorate as an effort to develop useful tools for fire analyses in nuclear power plants. The name OSFIC stands for "OilSpill Fires In Compartments". The purpose of this paper is to describe the code and to facilitate the use of the computer porgram. A more detailed description of the model, it's pupose and the physics involved is given in a separete paper. Chapter 2 gives a short description of the subroutines involved and the program flow. Chapter 3 gives a list of the main variables used in the program. Finnaly, an example of an interactive run is given in chapter 4. A printout of the code itself is given in Appendix A. The code of another computer program, HYDRO, is given in Appendix B. This is a very short program, developed to analyse hydrogen leakage scenarios.