A continuous development of new hardware and operating systems brings the importance of portable programming, which can be imported into multi-platform environment. Also, the recent development of computer communication technology brings us many choices of accessing into the other platforms, which also becomes a burden for the programmers who should consider developing software fitting into diverse platforms The present GNU system tools creates a part of the source code automatically, and suggests a direction towards a new platform. but the source code must be prepared by the programmer at the source level. In this paper, we describe design and implementation of on interactive tool for developing multi-platform software, The tool is designed to help a programmer to build a portable program for multi-platform, even though the programmer does not know very well about various UNIX platforms, And, the tool uses existing GNU system tools, such as autoconf, autoheader, automake and etc, and is able to insert a portable code into a right position by interacting with a programmer.