Determine type of file without extension

Strictly speaking, there is no such thing as "extension". This is some historical casus: in some old systems, there was an "extension" to the name of the file, which wasn't a part of the name. Presently, there is just the name; and there are naming conventions which are not mandatory and no longer effect any functionality. In Windows shell, those "extension" can be used for recognition of the "file types" recorded in the Registry where it is prescribed what operations can be performed at the Shell level for what file, using what application, with what command line.

No, without "extension", you cannot recognize those types. But even with "extension", it is often impossible. There is no any kind of OS-level universal mechanism. The rules for "extensions" are no rules; this is very loose mechanism. The same "extension" can be used for different formats and visa versa, or "extensions" not completely describe the type, as in case of media files. For an application, it can be a multi-step process. The file is attempted to open, the application looks at file signature (some first bytes at the very beginning), then examine "file header", and so on… There is nothing absolutely universal. Anyway, the OS does not care about it; you may need to develop your own file formats for your own applications, and so on…

Windows Explorer file name is not "explorer" as it looks on you picture; it is actually "Explorer.EXE". Look thoroughly. Remove the stupid "Folder Options" option "hide extension of known types".

—SA