Hello, I am currently using a Fortran program to run a simulation which involves an explicit differentiation loop. The program currently plots simulation data at specified time intervals using a subroutine with another program. I'd like to have the program also output data files at these specified times. I'd like to add one set of commands into the loop for the program to output the data files, but I cannot figure out a way for Fortran to name the files in some numerical order. Can anyone help? Thanks.