In order to solve a 3-dimensional problem by finite element method, a large stiffness matrix is required. A main storage of a computer is not enough for the request. So, auxiliary storages must be used.
　In conventional method, disks and direct access are used to assemble a stiffness matrix. This method takes much times to access and programing is difficult without those.
　In this paper, a new method is described. Magnetic tapes and sequential access are used to assemble and to solve a complate stiffness matrix.
　In the new method, named sequential file method, the procedure that contributions to a nodal point are calculated and add the contributions is iterated. Therefor, row elements of the complete stiffness matrix can be output sequentially to magnetic tapes each the iteration and so, the field for superposition of finite element stiffness matrices must not occupy the main storage or disks.
　To solve the complate matrix stored on magentic tapes, SOR iteration method is easily applied.
　This programing method can solve 5,000 nodal-points 3 dimensional problem using 32K storage compurter and magnetic tapes.