INT 24 - DOS 1+ - CRITICAL ERROR HANDLER
Note:   invoked when a critical (usually hardware) error is encountered; should
never be called directly

Critical error handler is invoked with:
AH = type and processing flags
bit 7 clear = disk I/O error
set   = -- if block device, bad FAT image in memory
-- if char device, error code in DI
bit 6  unused
bit 5 = 1 if Ignore allowed, 0 if not (DOS 3+)
bit 4 = 1 if Retry allowed, 0 if not (DOS 3+)
bit 3 = 1 if Fail allowed, 0 if not (DOS 3+)
bit 2 \ disk area of error  00 = DOS area  01 = FAT
bit 1 /                     10 = root dir  11 = data area
bit 0 = 1 if write, 0 if read
AL = drive number if AH bit 7 clear
BP:SI -> device driver header (BP:[SI+4] bit 15 set if char device)
DI low byte contains error code if AH bit 7 set
00h write-protection violation attempted
01h unknown unit for driver
02h drive not ready
03h unknown command given to driver
04h data error (bad CRC)
05h bad device driver request structure length
06h seek error
07h unknown media type
08h sector not found
09h printer out of paper
0Ah write fault
0Bh read fault
0Ch general failure
0Dh (DOS 3+) sharing violation
0Eh (DOS 3+) lock violation
0Fh invalid disk change
10h (DOS 3+) FCB unavailable
11h (DOS 3+) sharing buffer overflow
12h (DOS 4+) code page mismatch
13h (DOS 4+) out of input
14h (DOS 4+) insufficient disk space
STACK:  DWORD   return address for INT 24 call
WORD    flags pushed by INT 24
WORD    original AX on entry to INT 21
WORD    BX
WORD    CX
WORD    DX
WORD    SI
WORD    DI
WORD    BP
WORD    DS
WORD    ES
DWORD   return address for INT 21 call
WORD    flags pushed by INT 21
Handler must return:
AL = action code
00h ignore error and continue processing request
01h retry operation
02h terminate program through the equivalent of INT 21/AH=4Ch
(INT 20h for DOS 1.x)
03h fail system call in progress
SS,SP,DS,ES,BX,CX,DX preserved
Notes:  the only DOS calls the handler may make are INT 21/AH=01h-0Ch,30h,59h
if the handler returns to the application by popping the stack, DOS
will be in an unstable state until the first call with AH > 0Ch
for DOS 3.1+, IGNORE (AL=00h) is turned into FAIL (AL=03h) on network
critical errors
if IGNORE specified but not allowed, it is turned into FAIL
if RETRY specified but not allowed, it is turned into FAIL
if FAIL specified but not allowed, it is turned into ABORT
(DOS 3+) if a critical error occurs inside the critical error handler,
the DOS call is automatically failed

See also: 2195

24 - DOS 1+ - CRITICAL ERROR HANDLER