INT 21 - ELRES v1.0 only - INSTALLATION CHECK
AH = 4Bh
DS:DX = 0000h:0000h
Return: ES:BX -> ELRES history structure (see AH=2Bh/CX=454Ch)
DX = DABEh (signature, DAve BEnnett)
Note:   ELRES is an MSDOS return code (errorlevel) recorder by David H. Bennett

See also: 212B

214B - ELRES v1.0 only - INSTALLATION CHECK