Файл EX_

.ex_ is a compressed .exe executable file produced by Microsoft compression tools. An .ex_ file stores a complete Windows executable in a space-saving compressed form, without any ability to run it directly.

The idea behind the .ex_ format

.ex_ files are used for installer distribution purposes and to reduce file size. After installation, the files are decompressed and renamed back to their original .exe names. The naming convention follows a consistent rule: the last character of the original extension is replaced by an underscore - so .exe becomes .ex_, .dll becomes .dl_, .sys becomes .sy_, and so on. The format originates from early 1990s Microsoft tooling designed to fit programs onto space-constrained floppy disks.

The compressed data uses Microsoft's SZDD or KWAJ format (both LZ77-based), identifiable by the SZDD magic bytes (53 5A 44 44 88 F0 27 33) at offset 0. Newer installation media sometimes deliver these compressed files as named members inside a .cab archive, where the inner entry retains the .ex_ name. An .ex_ file is not a runnable program - it must be decompressed to recover the original .exe before it can be executed.

Creating and extracting .ex_ files

.ex_ files are generated from original .exe files using the Windows makecab command-line tool (or the older compress.exe). Reversing the process is possible by using the built-in Windows expand.exe tool or third-party archivers such as 7-Zip. The archive takes the same base name as the original .exe file, with only the extension's last character replaced by an underscore.