A Bash shell is an command line interpreter. Bash is Turing complete and even supports more advanced programming paradigms than those early BASIC machines did (eg functions, different scoping, more advanced debugging and error handling, forking, etc). This is all just built in commands - I'm not including any other POSIX user land. In the right hands, Bash is every bit as much a REPL environment as an interactive Python or LISP shell.

I don't understand why you're discounting Python here though. Would you mind explaining to me why a REPL BASIC shell is different from a REPL Python shell aside the 20 years age gap between them?

One last thing, as I noted in an earlier comment, most of those BASIC micro computers did also support other languages and shells. The later models of the BBC Micro came with LOGO in addition to BBC BASIC and also supported Fortran, LISP and a few other languages. My Amstrad CPC 464 runs Locomotive BASIC but I also have a CP/M disk for it. And around the same time (and a even a few years earlier) there were LISP machines and other computers which booted into other language shells.

BASIC wasn't unique nor special in the regard that you're praising it for. Neither back then then nor now. What made BASIC micro computers special was how simple the language BASIC was (otherwise we'd all be looking back fondly of our Fortran or LISP machines!). And this is why I make the distinction between the shell and the language. Because there's always been and always will be a large array of similar REPL shells - the key distinction between them being the accessibility of the language.

I considered saying the same thing about bash, but its really missing a big portion of what made BASIC exciting on those machines. That is the ability to draw graphics. Some of the other scripting languages with Tk linking might count though.

Frankly, I'm convinced javascript is the modern equivalent to BASIC. It is even complete with some horrible brain rotting syntax. But, it does provide both an easy barrier to entry (everyone has a web browser), the ability to show your results to others, and the fact that it remains in source form allows beginners to examine how something was achieved.

It depended upon the BASIC version, but the one you got on an IBM PC (the one embedded in the BIOS, usually only on PCs from IBM) was an odd cross between an editor and a REPL. Start out:

    PRINT "HELLO WORLD"

Press ENTER, and you get "HELLO WORLD" on the next line. Okay. Move the cursor up to the PRINT, hit the Insert key, type "10" then ENTER. You have now just entered a line into your program. Type LIST and you see

    10 PRINT "HELLO WORLD"

Move the cursor back up to line 10. Change the "10" to "20" and change "HELLO WORLD" to "IT IS GREAT TO BE HERE" and press ENTER. Reposition the cursor over the LIST command and press ENTER:

    10 PRINT "HELLO WORLD"
    20 PRINT "IT IS GREAT TO BE HERE"

Moving the cursor to the top of the screen wouldn't cause the display to scroll up, but that was more due to constrained resources than anything else. But other than that, the entire screen was the editor. Type in an expression to test it out. Go back up and fix it. Once it's fine, slap a number in front to add it to the program. As a REPL, it was vastly different than anything REPL I've seen since.

You can do that with Bash (albeit not with line numbers).

But as I said before, there were other languages available for said machines and those had their editors as well. What you're describing isn't a unique attribute to BASIC.