Int 10 Fn EF  - Video - Msherc.com - Get Video Adapter Type And Mode       [V]

   AH = EFh

Return: DL = video adapter type
       00h original Hercules
       01h Hercules Plus    (port 03BAh reads x001xxxxx)
       02h Hercules InColor (port 03BAh reads x101xxxxx)
       FFh not a Hercules-compatible card (port 03BAh bit 7 not pulsing)
   DH = memory mode byte
       00h "half" mode
       01h "full" mode
       FFh not a Hercules-compatible card
Program: MSHERC.COM/QBHERC.COM is a support program for the Microsoft Quick
     languages which makes their graphics libraries compatible with a
     Hercules card by adding video modes 08h and 88h, and supporting
     text in the new graphics modes.

Notes: while in mode 08h or 88h, INT 10 supports the Hercules card much like
     a CGA.
   MSHERC performs an installation check by setting DL=FFh and testing
     whether it has been changed on return, which causes it to reinstall
     itself when no HGC is present (or HGC emulation has temporarily been
     disabled); a better installation check would be to use DX=80FFh and
     check whether DX has been changed
   reportedly returns DH=00h on some not-entirely-Hercules-compatible
     cards
Index: installation check;MSHERC