INT 10H 05H: Select Video Page
Expects: AH 05H
AL video page number (0-based)
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
• Page-switching is not possible with MDAs.
• All newer computers are fast enough to update the screen in
place (see Video Memory Layouts).
• 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.
See Also: INT 10H: Video Services