[TUHS] What's In a Prompt String?

[Steve Nickolas via TUHS]

On Tue, 28 Apr 2026, segaloco via TUHS wrote:

> UNIX has had several ubiquitous PS1s: @, %, $ and then a PS2 of >, with 
> these values also being configurable.  I've seen in various BTL media 
> folks using a . (period) or occasionally a $ but with no space between 
> the prompt and the command.  I've always assumed the former was 
> influenced by DEC and the latter by IBSYS control cards (e.x. $JOB, 
> $EXECUTE, etc. pre-JCL stuff).
>
> Is there any history on the rationale for default PS1 selections between 
> various shells?  Worth noting that % seems to be the most commonly 
> implemented but $ is what more people are familiar with due to the 
> adoption of the Bourne shell by V7 and subsequently various standards. 
> I mention the % as more common as it seems to be default in a greater 
> number of shells despite Bourne family generally having more uptake 
> (afaik).
>
> Did these choices of symbols have any particular significance?  I can't 
> recall where I read it but I heard suggested the original UNIX shell 
> used '@' as a prompt as it looks like a snail shell.  Can't verify this, 
> nor do any stories of the other symbols come to mind.  I've found the 
> ubiquity of PS2 '>' in graphical icons for terminal emulators odd. 
> That's not a super common prompt to see on UNIX compared with the 
> others, I find it strange that is often the prompt character chosen for 
> icons, implying users are often sitting at a PS2 prompt?
>
> - Matt G.
>

At one point tcsh's default prompt was "> ".

Also CP/M and MS-DOS's "A>" could be an influence, and some BASIC 
interpreters had ">" prompts?

-uso.