Int 10 Fn 5049  - Video - Screenr V1.55+ - API                             [V]

   AX = 5049h ('PI')
   BX = function
       0000h installation check
       0001h lock mode
       0002h unlock mode
       0003h lock palette
       0004h unlock palette

Return: AX = 0000h if installed
       BX = TSR version (BH=major,BL=minor)
       CL = mode locking status
       00h mode not locked
       01h mode locked: INT 10/AH=00h disabled
       CH = palette locking status
       00h palette not locked
       01h palette locked, the following functions are disabled:
           AX=1000h, AX=1001h, AX=1002h, AX=1010h, AX=1012h
Program: SCREENR is a TSR supplied with Patrick Ibbetson's SCREEN display
     utility.
Index: installation check;SCREENR