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     Video mode and adapter combinations not listed above support one
     display page (for example, a Monochrome Display Adapter (MDA) in
     mode 7).
 
     Switching between pages does not affect their contents. In
     addition, text can be written to any video page with Int 10h
     Functions 02h, 09h, and 0Ah, regardless of the page currently
     being displayed.
 
     On the PCjr, the CPU page determines the part of the physical
     memory region 00000h-1FFFFh that will be hardware mapped onto 16K
     of memory beginning at segment B800h. The CRT page determines the
     starting address of the physical memory used by the video
     controller to refresh the display. Smooth animation effects can be
     achieved by manipulation of these registers.
 
     Programs that write directly to the B800h segment can reach only
     the first 16K of the video-refresh buffer. Programs requiring
     direct access to the entire 32K buffer in modes 09h and 0Ah can
     obtain the current CRT page from the ROM BIOS variable PAGDAT at
     0040:008Ah.
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