Query about Emacs Process API | Asynchronous processes

[Narendra Joshi]

Hi,

Reading through Emacs Lisp info manual, I found out
[[info:elisp#Asynchronous Processes][info:elisp#Asynchronous Processes]]
that it's possible to create an asynchronous process (let's ignore
network processes for now) without any command at all. For example,

#+begin_src emacs-lisp
(make-process :name "a-pty-process" :command (list nil) :buffer 
"*a-pty-process-buffer*")
#+end_src

This creates a process with a pseudo terminal. This process is shown by
`list-processes`

#+begin_src 
 Process ▼ PID Status Buffer TTY Thread Command 
a-pty-process   -2      run     *a-pty-process-buffer*    /dev/pts/1   Main     
    
#+end_src

^ The process ID is a negative number. It makes me think that there is
no real sub-process (OS level) yet. Is that true? If not, what is being
executed by the sub-process?

I am wondering what the use cases are that such a feature serves.   

Thanks,
-- 
Narendra Joshi