Vertical Arabic text?

Hi all -

I was at an event last night on the topic of outsourcing and one of the
tables was decorated with flags. One flag, ostensibly Pakistani, had
Arabic or similar text along the left vertical edge. Clearly, the text
was written in vertical orientation, which I had never seen before for
that script. So one question that came to mind is, is Arabic written
vertically, and if so, when? And also, if so, then is it written bottom
to top or top to bottom?

Best,

Barry