Previously, a major problem with the way GS/OS handled open files was that unrelated programs could affect each other's open files. For example, a Desk Accessory (or a background program of any sort) could open a file and have it closed without it's knowledge by the main application program. This presented all kinds of problems for desk accessory authors. Apple presented a partial solution with System Software 5.0.4, but it wasn't enough for a true multitasking environment. GNO/ME keeps track of exactly which process opened which file. It also discontinues the concept of a global File Level, opting instead for a per-process File Level. Any operations a process performs on a file (opening, closing, etc.) do not affect any other process' files.
In addition to this behavior, when a process terminates in any manner all files that it currently has opened will be closed automatically. This prevents problems of the sort where a program under development terminates abnormally, often leaving files open and formerly necessitating a reboot.
The Flush GS/OS call is not modified in this manner as its effects are basically harmless.
The Close call accepts a refNum parameter of 0 (zero), to close all open files. This works the same way under GNO/ME, except of course that only the files of the process calling Close are in fact closed.