Compatibility: EGA VGA
Expects: AH    12H
BL    20H
Returns: (none)
Info: This redirects the INT 05H (print screen) vector to a handler
within the EGA/VGA ROM-BIOS.

On older PCs, XTs, and ATs, the default ROM-BIOS print-screen
handler stops printing after 25 lines.  The EGA/VGA handler
correctly prints the number of lines specified in the byte at
0040:0084 in the BIOS Data Area.

Notes: Most EGAs and VGAs set this automatically.  However, it is good
practice to use this fn whenever you change the number of video
lines that are displayed in text mode.

See Also: INT 10H 12H (EGA/VGA Special Functions/Alternate Select)
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INT 10H 12H BL=20H: Select Alternate Print Screen Handler