Int 21 Fn 8C  - European MS-dos 4.0 - Set Signal Handler                   [D]

   AH = 8Ch
   AL = signal number (see below)
   BL = action (see below)
   DS:DX -> signal handler

Return: CF clear if successful
       AL = previous action
       ES:BX -> previous signal handler
   CF set on error
       AX = error code (01h,invalid SigNumber or Action) (see AH=59h)
Desc:  set the routine which will be invoked on a number of exceptional
     conditions

Note:  all signals will be sent to the most recently installed handler

See Also: AH=8Dh

Values for signal number:
 01h   SIGINTR     Control-C or user defined interrupt key
 08h   SIGTERM     program termination
 09h   SIGPIPE     broken pipe
 0Dh   SIGUSER1    reserved for user definition
 0Eh   SIGUSER2    reserved for user definition

Values for signal action:
 00h   SIG_DFL     terminate process on receipt
 01h   SIG_IGN     ignore signal
 02h   SIG_GET     signal is accepted
 03h   SIG_ERR     sender gets error
 04h   SIG_ACK     acknowledge received signal and clear it, but don't
           change current setting

Signal handler is called with:
   AL = signal number
   AH = signal argument

Return: RETF, CF set: terminate process
   RETF, CF clear, ZF set: abort any interrupted system call with an error
   RETF, CF clear, ZF clear: restart any interrupted system call
   IRET: restart any interrupted system call

Note:  the signal handler may also perform a nonlocal GOTO by resetting the
     stack pointer and jumping; before doing so, it should dismiss the
     signal by calling this function with BL=04h