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1A00

Category: BIOS

INT 1A - TIME - GET SYSTEM TIME

	AH = 00h
Return: CX:DX = number of clock ticks since midnight
	AL = midnight flag, nonzero if midnight passed since time last read
Notes:	there are approximately 18.2 clock ticks per second, 1800B0h per 24 hrs
	  (except on Tandy 2000, where the clock runs at 20 ticks per second)
	IBM and many clone BIOSes set the flag for AL rather than incrementing
	  it, leading to loss of a day if two consecutive midnights pass
	  without a request for the time (e.g. if the system is on but idle)
	since the midnight flag is cleared, if an application calls this
	  function after midnight before DOS does, DOS will not receive the
	  midnight flag and will fail to advance the date
	Modern releases of MS-DOS/PC DOS (5.0+???) assume that AL is a day
	  rollover counter rather than a flag, as expected by older releases.
	  DOS 5 - 7.10 (Windows 98 SE) provide an undocumented CONFIG.SYS
	  SWITCHES=/T option to force the old behaviour of the day advancing
	  code, that is using a flag instead of a counter.
	DR DOS 3.31 - DR-DOS 7.03 handle AL as a flag.
SeeAlso: AH=01h,AH=02h,INT 21/AH=2Ch,INT 55"Tandy 2000",INT 4E/AH=02h"TI"
SeeAlso: INT 62/AX=0099h,MEM 0040h:006Ch,MEM 0040h:0070h

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  Copyright 2000   by Ralf Brown     Updated Jul 2000