[en] Graphics processing at JAERI mainly has been executed on mainframe computers with Calcomp compatible graphics libraries. With spread of engineering workstations (EWS), it is important that those enormous graphics softwares be able to be carried out on EWS. The Calcomp compatible interface library 'piflib' has been developed on the X Window System, which is the most popular window environments on EWS. In this report, specifications of the library 'piflib' and its usages are presented. The cooperative processing with mainframe computers is also described. (author)