Compatibility: All
Expects: AH    05H
AL    video page number (0-based)
                                                                  
Returns: (none)
                                                                  
Info: This selects a different video page.  CGAs,EGAs, and VGAs support
eight video pages, but most MDAs  support only one.

Historically, some text-mode programs have gotten a performance
boost by using multiple video pages.  For instance, you can make
a series of changes to the second video page and then use this fn
to display the entire page all at once.

Notes:   On VGAs, you may use INT 10H 1bH (get functionality/state info)
to see how many pages the active display supports.

  Most programmers select page 0 and leave it there for these
reasons:
  Page-switching is not possible with MDAs.
  All newer computers are fast enough to update the screen in
  On older CGAs, writing to non-visible pages still causes
Video Snow (so there is no performance gain).
  Some popular mouse support driver will honor only page 0.

However, TSRs should be aware of page-switching techniques in
order to avoid screwing up the interrupted application.

  The active video page number can be obtained via INT 10H 0fH.

  The starting address of the start of the active page can be
found in the 2-byte word at 0040:004e.  See BIOS Data Area.

- -

INT 10H 05H: Select Video Page