Function TextImageSize(X1,Y1,X2,Y2:Word):LongInt

    Updates VX and VY       : No
    Updates Cursor Position : No

    This returns the amount of  memory  required  to hold a text image in
    memory.   Although  a  LongInt  is  returned,  only  a  value  up  to
    32 kb is permitted by VGA and SVGA cards at this time.

    I think back to CGA  (16  kb)  cards  and  everyone  thought 64 kb of
    display memory was a lot  and  I  feel  I  had  better use a LongInt,
    even though only 32 kb of text display is permitted.