[en] The Steady State Porous Body Assembly Code (SPAC) was derived directly from the ENERGY III code, which was developed and reported by Dr. E.U. Khan. The ENERGY III code was part of a code series, including the ENERGY I and ENERGY II codes, that Dr. Khan used as a test bed for the porous body models, on which his Doctoral thesis (MIT) was based. The ENERGY III code itself, as initially written, required extensive computer core space to execute, was fairly costly (slow) to use, and suffered truncation errors that were quite noticeable. In contrast, the SPAC code requires only 7% of the space, 3% of the run time, and 2.5% of the expense that are required to use ENERGY III. The truncation errors have been eliminated and this report is intended to produce sufficient documentation. At this stage, the SPAC code is a useful code for evaluating the temperature and flow conditions under forced or mixed convection conditions. It is a significant improvement on the ENERGY III code (and the simpler ENERGY I and II codes), although it uses the same model and equations. Not all of the quirks inherited from ENERGY III have been eliminated from SPAC, but those remaining are merely inconvenient and do not pose serious problems