This workbook solves a simple one-dimensional, steady-state conduction equation by finite-difference methods.  Such a system results in a tridiagonal system of linear equations.  The left side of this plane wall is adiabatic by symmetry; the right side is exposed to convection.  This workbook demonstrates the solution of the coupled set of equations by a simple iteration scheme.  It also implements a direct solution of the tridiagonal system using a VBA version of the LAPACK routine for tridiagonal systems (SGTSV).