What is a vertical tab?

What was the original historical use of the vertical tab character (\v in the C language, ASCII 11)?

Did it ever have a key on a keyboard? How did someone generate it?

Is there any language or system still in use today where the vertical tab character does something interesting and useful?

Vertical tab was used to speed up printer vertical movement. Some printers used special tab belts with various tab spots. This helped align content on forms. VT to header space, fill in header, VT to body area, fill in lines, VT to form footer. Generally it was coded in the program as a character constant. From the keyboard, it would be CTRL-K.

I don't believe anyone would have a reason to use it any more. Most forms are generated in a printer control language like postscript.

@Talvi Wilson noted it used in python '\v'.

print("hello\vworld")

Output:

hello
     world

The above output appears to result in the default vertical size being one line. I have tested with perl "\013" and the same output occurs. This could be used to do line feed without a carriage return on devices with convert linefeed to carriage-return + linefeed.

Microsoft Word uses VT as a line separator in order to distinguish it from the normal new line function, which is used as a paragraph separator.

In the medical industry, VT is used as the start of frame character in the MLLP/LLP/HLLP protocols that are used to frame HL-7 data, which has been a standard for medical exchange since the late 80s and is still in wide use.

It was used during the typewriter era to move down a page to the next vertical stop, typically spaced 6 lines apart (much the same way horizontal tabs move along a line by 8 characters).

In modern day settings, the vt is of very little, if any, significance.