### Ctrl

Wikipedia had this for the `Ctrl` key:

```
^X Traditional notation
C-x Emacs notation
CTRL-X Old Microsoft notation
Ctrl+X New Microsoft notation
Ctrl/X OpenVMS notation
```

I'm adding [1]:

```
Ctrl_N
Ctrl--N
```

Corresponding for `Alt`, excluding trivial ones that follow from above such as `Alt+X`

, would be:

### Alt

```
^[x
M-x
Mod1 x (seen in e.g. Fluxbox config)
```

### "Windows logo" button

```
s-x
Win+X
Super+X
Mod4 x
```

...but compiling a full list is not possible (if someone wants to try here, feel free to edit my post). Your best bet is to use search engines to find the correct notation for your current application from case to case.