This paper is written to present the design purpose and design process of the Multiple Window Editor. Multiple Window Editor is a software which allows the user to edit or view different files or the same file on the screen by the window facilities provided by this software. All the windows can be dynamically created, changed, moved, and destroyed. The main purpose of this program is to improve the programming environment for the users. The design motivations will be introduced through the comparison of the present existing window facilities and the editor components. The design process will be introduced by analyzing the design decision, design tradeoffs and implementation problems.