In this subroutine the input (.inp) and output files (.dat, .frd, .sta, .onf) are opened. The .dat file contains data stored with *NODE PRINT and *EL PRINT, the .frd file contains data stored with *NODE FILE and *EL FILE, the .sta file contains information on the convergence of the calculation. The .onf file is used if subsequently the program TOSCA is run.