How to bind C-`(backquote) in emacs

Question

I would like to bind C-` (control-backquote), but I could not do this.

Sex

 (global-set-key "\M-`" 'other-window) 

works whereas

 (global-set-key "\C-`" 'other-window) 

not. It does not work with the error "Invalid modifier in line".

Answer 1

"\Ca" and the like work because there is an ASCII code for them. For C-doesn’t exist, just use

 (kbd "C-`") 

By the way, it is often more portable from one emacsen to another.

Answer 2

Since it is fair to answer my own question:

 (global-set-key [?\C-`] 'other-window) 

But I do not know the meaning of this additional question mark.