The report documents the archiving of computer files used in the modified modular finite-difference flow model and post-processor programs for the Columbia Plateau regional aquifer system in parts of Washington, Oregon, and Idaho. The files are obtainable on magnetic tape from the U.S. Geological Survey, WRD, Pacific Northwest District Office, 1201 Pacific Avenue, Suite 600, Tacoma, Washington 98402. There are five files containing source codes of the flow model and post-processors. Input for the flow model is stored in 51 files and grouped into 16 categories, one for each of the packages of the model except its utility package. Model output is in 18 files. The postprocessors have four files, two with input control and two with output. Five command-input files compile and load the flow model, run it, and run the postprocessors .