You mentioned command line, whatever this means...
Now in past (very past) when one need to control external devices by 'type writers' aka 'terminals' it was very common to send control codes by Ctrl&<x>
What means now <x>?
Have a look to the Ascii table e.g. here
File:ASCII-Table-wide.svg - Wikipedia[
^] and also
American Standard Code for Information Interchange – Wikipedia[
^] (where you find STX, ETX)
And let us first have a look to <cr>, Carriage return, decimal 13. Third row right you will find character 'M'.
Don't ask me from where it comes but Ctrl&M will perfrom a 'Carriage return' (and this still works e.g. in notepad).
And same is/was valid for other control characters, so Ctrl&B was/is(?) STX etc.
So, for every control character in the very past you could use Ctrl&<x> to send a control character.
In your case
STX is Ctrl&B
ETX is Ctrl&C
Sorry for my English ;)