Category: vendor-specific BIOS extensions
Flags: callout or callback (usually hooked rather than called)

INT 57 - TI Professional PC - CRT MAPPING HOOK

	AX/BX/CX/DX/BP/SI/DI same as on entry to CRT subroutine (e.g. INT 49)
	DS = BIOS system segment
	ES = DE00h
Return: DF/IF flags must be preserved
	ES,DS,BP preserved
	AX,BX,CX,DX,SI,DI may be changed as necessary to modify the original
Desc:	hooking this vector permits programs to intercept or modify all
	  screen output, including both application calls to INT 49 and
	  calls generated internally by the BIOS which bypass INT 49
Note:	by default, this vector points at an IRET instruction
SeeAlso: INT 49/AH=01h"TI",INT 50"TI Professional"