An application that recognizes long file names might be run on systems with or without installable file systems. Additionally, the maximum length of a file name might vary from one installable file system to another. So that an application can properly handle this variable condition (and, for example, allocate large enough buffers to hold file names), the application should call DosQuerySysInfo to determine the maximum path length supported by the file system.
Make this call before calling file system functions that require full path names.