One step file association. This utility did the job of both ASSOC and FTYPE, in one step. ASSOCIATE assigns an extension directly with an executable application by adding a new FileType to the system registry.
Syntax
ASSOCIATE .ext filename [/q /d /f]
Key
.ext : Extension to be associated.
filename : Executable program to associate .ext with.
/q : Quiet - Suppress interactive prompts.
/f : Force - Force overwrite or delete without questions.
/d : Delete - Delete the association.
Microsoft have changed how file associations work from Windows 8 /2012 onward to prevent malicious apps from changing file associations on the fly. It is no longer possible to use the registry, FTYPE or ASSOCIATE for file association hijacking.
In Pre-Win 8, apps could set the default handler for a file type/protocol by manipulating the registry, this means you could easily have a script or a group policy manipulating the registry. However In Win 8, the registry changes are verified by a hash (unique per user and app) that detects tampering by apps. In the absence of a valid hash, we ignore the default in the registry. Microsoft have introduced a new Group Policy mechanism for declaring these defaults in Win 8 to accommodate this type of scenario...
The way Microsoft expect you to change this now is with an xml file applied through Group Policy. Instructions here.
The Settings pane will only display installed applications (FileTypes) and/or an option to install apps from the Windows store. There is no option to manually add a file association for a non-Windows store application.
Christoph Kolbicz has reverse engineered the hashing algorithm and created a tool called SetUserFTA to set the file type association on a single machine.
A file extension is the last few characters in a Filename after
the period.
So a file called JANUARY.HTML has the file extension .HTML
The File extension is used by Windows NT to determine the type of information
stored in the file and therefore which application(s) will be able to display
the information in the file. File extensions are not case sensitive and are
not limited to 3 characters.
Add a File Association.
To add the File Type "SQLfile"=Notepad.exe and also set the File Association
of .SQL="SQLfile" run this command:
ASSOCIATE .SQL Notepad.exe
This is equivalent to the two commands
FTYPE sqlfile="C:\Program Files\Syatem32\notepad.exe" "%1"
ASSOC .sql=sqlfile
Remove a File Association:
ASSOCIATE .SQL /d
Note that /d will delete the File Association but will NOT delete the File Type. You can achive the same with the standard command:
ASSOC .SQL=
File types created by Associate.exe are always given a name in the form xxxfile, where xxx is the file extension.
“The earth does not belong to man.... man belongs to the earth” ~ Chief Seattle
ASSOC - Change file extension associations.
FTYPE - Display or modify file types used in file extension associations.