Page number in BIOS interrupts

There's enough video memory to allow multiple text screens side-by-side. The page numbers allow you to do double-buffering, where you draw to an off-screen page, and then when it's ready change the currently visible page to the new one.

See the infamous and still invaluable Ralph Brown's Interrupt List for more (well, a little more) information:

http://www.ctyme.com/intr/rb-0087.htm

In particular, look at int 0x10 AH=0x05, which lets you change the current visible page.

Just use page 0, which is the default current page.