INT 15 UC - OS HOOK - ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. TRACING CALLOUT (PS30IBM PS/2 Model 30 and below/286,PS50Z,PS95)
	AH = C5h
	AL = interrupt being invoked
	    01h INT 19
	    02h INT 14
	    03h INT 16
	    04h INT 40 (floppy INT 13)
	    05h INT 17
	    06h INT 10
	    07h INT 12
	    08h INT 11
	    09h INT 1A
Return: all registers except AX must be preserved
Notes:	called as the very first action of the indicated ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. interrupt
	  handlers on the PS/2IBM PS/2, any model Models 30/286, 50Z, and 95
	default handler does nothing and returns CF clear for the above
	  subfunctions, CF set and AH=86h for all other subfunctions
	value of AX passed to the original interrupt handler is pushed on
	  stack immediately prior to call