INT 21 - ELRES v1.1 - INSTALLATION CHECK
AH = 2Bh
CX = 454Ch ('EL')
DX = 5253h ('RS')
Return: ES:BX -> ELRES history structure (see below)
DX = DABEh (signature, DAve BEnnett)
Note:   ELRES is an MSDOS return code (errorlevel) recorder by David H. Bennett
which stores recent errorlevel values, allows them to be retrieved
for use in batch files, and can place them in an environment variable
SeeAlso: AH=4Dh

Format of ELRES history structure:
Offset  Size    Description
00h    WORD    number of return codes which can be stored by following buffer
02h    WORD    current position in buffer (treated as a ring)
04h  N BYTEs   ELRES buffer

See also: 214B

212B - ELRES v1.1 - INSTALLATION CHECK