The majority of the IUEDAC IUESIPS-related software was written to use RDAF-format files, even though the official format used by the IUE project and the format in which data was both archived and delivered to IUE guest observers was known as GO-format. Back when the IUEDAC first opened and all work was done using a PDP 11/44 computer, it was found that the data could be accessed more quickly if the VICAR label and data were stored in separate disk files. In the process it was also decided to redefine some of the header record entries. The resulting file format has become known as RDAF-format. (Note the "GO-split" format is similar to RDAF-format except that the header record entries are not modified.)