INT 2F U - DOS 3+ CRITICAL ERROR HANDLER - EXPAND ERROR INTO STRING
AH = 05h
---DOS 3.x---
AL = extended error code (not zero)
---DOS 4+ ---
AL = error type
01h DOS extended error code
02h parameter error
BX = error code
Return: CF clear if successful
ES:DI -> ASCIZ error message (read-only)
AL = ???
CF set if error code can't be converted to string
Notes:  called at start of COMMAND.COM's default critical error handler if
installed by a user program, allowing partial or complete overriding
of the default error message
subfunction 02h called by many DOS 4 external programs
SeeAlso: INT 24

See also: 2F122E

2F05 - DOS 3+ CRITICAL ERROR HANDLER - EXPAND ERROR INTO STRING