The File Retrieval and Editing SyStem, or FRESS, was a hypertext system developed at Brown University in 1968 by Andries van Dam and his students, including Ted Nelson and Bob Wallace. FRESS was a continuation of work done on van Dam's previous hypertext system, HES, developed the previous year. FRESS ran on an IBM 360-series mainframe running VM/CMS. It implemented one of the first virtual-terminal interfaces, and could run on various terminals from dumb typewriters up to the Imlac PDS-1 graphical minicomputer. On the PDS-1, it supported multi-window WYSIWYG editing and graphics display. Notably, the PDS-1 used a lightpen rather than a mouse, and the lightpen could be "clicked" using a cathartic foot-pedal.