Apparatus and method for porting applications to different platforms. The apparatus and method use a mapping table function that receives source filenames and directory structures and maps them to filenames and directory structures appropriate for a target platform. In a preferred embodiment, the apparatus and method map flexible filenames and directory structures, such as is found with the Unix filesystem, to more restrictive filenames and directory structures, such as is found with the OS/400 filesystem. In this way, an application developer may make use of the more flexible filesystem of conventions such as Unix, when developing application files and use the apparatus and method to automatically handle converting these more flexible filenames and directory structures to the more restrictive filenames and directory structures of platforms to which the application is to be ported.