What's the lowest allowed character in a filename?

[Reljoy]

What's the lowest allowed (alphabetically) character in a filename?
I want a file to appear at the top of the list in a folder so it is always seen first.
In Windows XP I could do this by starting the filename with a !
When I did that in Mint it went to the bottom of the list instead.
I tried to start with a ~ and got the same result
Interestingly, I discovered that if I started the filename with a~ and ended it with ~ it changed to a backup file.
Is a the lowest character for sorting?

[jroa]

I am not sure why you are having an issue, but mine sorts with the numbers at the top, then the letters with "a" being the first.

Maybe you can name your file with a 1 as the first character?

[Reljoy]

thanks, I should have thought of numbers.
Interestingly, in my first post, I typed in tilde a couple of times and it shows up as a hyphen when it was submitted - as in
a tilde a~
filename tilde filename~
The tilde gets changed to a hyphen -