A general purpose FORTRAN code is described for the computations of three dimensional steady heat transfer and fluid flow in rectangular geometries. The code is designed to handle combined conduction convection problems within domains comprising of both solid and fluid regions. This is accomplished through the use of the harmonic mean formulation for evaluating interface diffusivities. A control volume formulation is used to discretize the governing equations for the dependent variables in the primitive form. The velocity-pressure coupling is handled by the SIMPLER algorithm. THe iterative solution scheme employs the tri- diagonal matrix algorithm of Thomas. A sample example of three-dimensional natural convection in a rectangular enclosure is used to validate the code against existing numerical solutions.