NOTE:  The following tables were compiled by:
		Michael L. Mohle'			Princeton-Galax Systems
		9 Grover Ave				Princeton, NJ 08540
		(609) 924-4149 (evenings)
		CIS: 76340,650				Source: BEA751

No claims of accuracy are made.  The sources are many, including IBM and other
manufacturer documentation, numerous books, other compilations of a similar
nature, and a number of years working with PC-class machines. If you find any
errors or have anything to add, please let me know.  My goal is to provide a
good reference tool. -- MLM

	*** CONTENTS OF THIS FILE ARE HEREBY RELEASED TO THE PUBLIC DOMAIN ***

PC Compatible Low-Memory Map								PGS -- Page   1

Interrupt Vectors (0000-003F)
-----------------------------

Addr  Int  Function
--------------------------------------------------------------------------------
0000  00h  CHIP Divide by zero
0004  01h  CHIP Single-step
0008  02h  CHIP NMI (Non-Maskable-Interrupt)
000C  03h  CHIP Breakpoint (1-byte-Interrupt)
0010  04h  CHIP Overflow on INTO
0014  05h  BIOS Print-screen Key | 286 Bound-Check-Failed
0018  06h  286  Undefined Opcode
001C  07h  286  No math unit available
--------------------------------------------------------------------------------
0020  08h  BIOS IRQ_0 Time of day		(Vectored Hardware Line)
0024  09h  BIOS IRQ_1 Keyboard		(Vectored Hardware Line)
0028  0Ah  BIOS IRQ_2 Reserved		(Vectored Hardware Line)
002C  0Bh  BIOS IRQ_3 Serial port		(Vectored Hardware Line)
0030  0Ch  BIOS IRQ_4 Serial port		(Vectored Hardware Line)
0034  0Dh  BIOS IRQ_5 Alt. printer 	(Vectored Hardware Line)
0038  0Eh  BIOS IRQ_6 Diskette		(Vectored Hardware Line)
003C  0Fh  BIOS IRQ_7 Printer 		(Vectored Hardware Line)
--------------------------------------------------------------------------------
0040  10h  BIOS Video
0044  11h  BIOS Equipment check
0048  12h  BIOS Memory size
004C  13h  BIOS Diskette
0050  14h  BIOS Serial communications
0054  15h  BIOS Cassette, 286 extended I/O
0058  16h  BIOS Keyboard
005C  17h  BIOS Printer
--------------------------------------------------------------------------------
0060  18h  BIOS ROM BASIC entry
0064  19h  BIOS Bootstrap
0068  1Ah  BIOS Time of day
006C  1Bh  BIOS Keyboard-break
0070  1Ch  BIOS Timer-tick
0074  1Dh  BIOS Video initialization
0078  1Eh  BIOS Floppy parameters
007C  1Fh  BIOS Graphics Chars (EGA)
--------------------------------------------------------------------------------
0080  20h  DOS Program termination
0084  21h  DOS Function Calls
0088  22h  DOS Terminate Address
008C  23h  DOS Ctrl-break Exit
0090  24h  DOS Critical Error Handler
0094  25h  DOS Absolute sector read
0098  26h  DOS Absolute sector write
009C  27h  DOS Terminate, stay resident
--------------------------------------------------------------------------------
00A0  28h  DOS Internal KEYBOARD_BUSY_LOOP
00A4  29h  DOS Internal FAST_PUTCHAR
00A8  2Ah  DOS Internal (IRET)
00AC  2Bh  DOS Internal (IRET)
00B0  2Ch  DOS Internal (IRET)
00B4  2Dh  DOS Internal (IRET)
00B8  2Eh  DOS Internal EXECUTE-COMMAND
00BC  2Fh  DOS Multiplex
--------------------------------------------------------------------------------
00C0  30h  DOS Internal (Not a vector! - FAR JMP for CP/M-style calls)
00C4  31h  DOS Internal
00C8  32h  DOS Reserved (IRET)
00CC  33h  Microsoft Mouse
00D0  34h  Turbo-C Floating-Point Emulator
00D4  35h  Turbo-C Floating-Point Emulator
00D8  36h  Turbo-C Floating-Point Emulator
00DC  37h  Turbo-C Floating-Point Emulator
--------------------------------------------------------------------------------

PC Compatible Low-Memory Map								PGS -- Page   2

Interrupt Vectors (0000-003F)
-----------------------------

Addr  Int  Function
--------------------------------------------------------------------------------
00E0  38h  Turbo-C Floating-Point Emulator
00E4  39h  Turbo-C Floating-Point Emulator
00E8  3Ah  Turbo-C Floating-Point Emulator
00EC  3Bh  Turbo-C Floating-Point Emulator
00F0  3Ch  Turbo-C Floating-Point Emulator
00F4  3Dh  Turbo-C Floating-Point Emulator
00F8  3Eh  Turbo-C Floating-Point Emulator
00FC  3Fh  MS-LINK overlay manager
--------------------------------------------------------------------------------
0100  40h  BIOS (DISK) Floppy-disk handler (relocated INT 13h)
0104  41h  BIOS (DISK) Primary Fixed-Disk parameters
0108  42h  BIOS (EGA) Video handler (relocated INT 10h)
010C  43h  BIOS (EGA) Initialization parameters
0110  44h  BIOS (EGA) Fonts
0114  45h  BIOS Reserved
0118  46h  BIOS (DISK) Secondary Fixed-Disk parameters
011C  47h  BIOS Reserved (IRET)
--------------------------------------------------------------------------------
0120  48h  BIOS Reserved (IRET)
0124  49h  BIOS Reserved (IRET)
0128  4Ah  BIOS (AT) Real Time Clock Alarm (IRET)
012C  4Bh  BIOS Reserved (IRET)
0130  4Ch  BIOS Reserved (IRET)
0134  4Dh  BIOS Reserved (IRET)
0138  4Eh  BIOS Reserved (IRET)
013C  4Fh  BIOS Reserved (IRET)
--------------------------------------------------------------------------------
0140  50h  BIOS (AT) Real Time Clock (IRET)
0144  51h  BIOS Reserved (IRET)
0148  52h  BIOS Reserved (IRET)
014C  53h  BIOS Reserved (IRET)
0150  54h  BIOS Reserved (IRET)
0154  55h  BIOS Reserved (IRET)
0158  56h  BIOS Reserved (IRET)
015C  57h  BIOS Reserved (IRET)
--------------------------------------------------------------------------------
0160  58h  BIOS Reserved (IRET)
0164  59h  BIOS Reserved (IRET)
0168  5Ah  BIOS Reserved (IRET)
016C  5Bh  BIOS Reserved (IRET)
0170  5Ch  BIOS Reserved (IRET)
0174  5Dh  BIOS Reserved (IRET)
0178  5Eh  BIOS Reserved (IRET)
017C  5Fh  BIOS Reserved (IRET)
--------------------------------------------------------------------------------
0180  60h  User programs (NULL)
0184  61h  User programs (NULL)
0188  62h  User programs (NULL)
018C  63h  User programs (NULL)
0190  64h  User programs (NULL)
0194  65h  User programs (NULL)
0198  66h  User programs (NULL)
019C  67h  LIM EMS (User programs)
--------------------------------------------------------------------------------
01A0  68h  Not used (IRET)
01A4  69h  Not used (IRET)
01A8  6Ah  Not used (IRET)
01AC  6Bh  Not used (IRET)
01B0  6Ch  Not used (IRET)
01B4  6Dh  Not used (IRET)
01B8  6Eh  Not used (IRET)
01BC  6Fh  Not used (IRET)
--------------------------------------------------------------------------------

PC Compatible Low-Memory Map								PGS -- Page   3

Interrupt Vectors (0000-003F)
-----------------------------

Addr  Int  Function
--------------------------------------------------------------------------------
01C0  70h  BIOS (AT) IRQ_9  Redirect
01C4  71h  BIOS (AT) IRQ_10 Redirect
01C8  72h  BIOS (AT) IRQ_11 Redirect
01CC  73h  BIOS (AT) IRQ_12 Redirect
01D0  74h  BIOS (AT) IRQ_13 Redirect
01D4  75h  BIOS (AT) IRQ_14 Redirect
01D8  76h  BIOS (AT) INT_87 Redirect
01DC  77h  BIOS (AT) IRQ_15 Redirect
--------------------------------------------------------------------------------
01E0  78h  Not Used (NULL)
01E4  79h  Not Used (NULL)
01E8  7Ah  Not Used (NULL)
01EC  7Bh  Not Used (NULL)
01F0  7Ch  Not Used (NULL)
01F4  7Dh  Not Used (NULL)
01F8  7Eh  Not Used (NULL)
01FC  7Fh  Not Used (NULL)
--------------------------------------------------------------------------------
0200  80h  BASIC while in interpreter
 ...
03C0  F0h  BASIC while in interpreter
--------------------------------------------------------------------------------
03C4  F1h  User Interrupt (NULL)
03C8  F2h  User Interrupt (NULL)
03CC  F3h  User Interrupt (NULL)
03D0  F4h  User Interrupt (NULL)
03D4  F5h  User Interrupt (NULL)
03D8  F6h  User Interrupt (NULL)
03DC  F7h  User Interrupt (NULL)
03FC  F8h  User Interrupt (NULL)
03E0  F8h  User Interrupt (NULL)
03E4  F9h  User Interrupt (NULL)
03E8  FAh  User Interrupt (NULL)
03EC  FBh  User Interrupt (NULL)
03F0  FCh  User Interrupt (NULL)
03F4  FDh  User Interrupt (NULL)
03F8  FEh  User Interrupt (NULL) Destroyed on AT in protected mode (Ext. Memory)
03FC  FFh  User Interrupt (NULL) Destroyed on AT in protected mode (Ext. Memory)
--------------------------------------------------------------------------------

PC Compatible Low-Memory Map								PGS -- Page   4

ROM BIOS Data Area Map (0400-04EF)
----------------------------------

Addr | Ln | Function
-----+----+---------------------------------------------------------------------
0400 | 08 | COM1, COM2, COM3, COM4 Base I/O-addresses
-----+----+---------------------------------------------------------------------
0408 | 08 | LPT1, LPT2, LPT3, LPT4 Base I/O-addresses
-----+----+---------------------------------------------------------------------
0410 | 02 | EQUIPMENT Flags		   76543210 76543210
	|	|   # printers 	    C0  xx...... ........
	|	|   Serial printer	    20  ..x..... ........
	|	|   Game adapter	    10  ...x.... ........
	|	|   # Serial ports	    0E  ....xxx. ........
	|	|   No DMA		    01  .......x ........
	|	|   # Diskette drives   C0  ........ xx...... (00=1, 01=2, 10=3, 11=4)
	|	|   Initial video mode  30  ........ ..xx.... (10=Co80, 11=Mono)
	|	|   Not used		    0C  ........ ....xx..
	|	|   Math coprocessor    02  ........ ......x.
	|	|   Disk drives present 01  ........ .......x
-----+----+---------------------------------------------------------------------
0412 | 01 | BOOT flags
-----+----+---------------------------------------------------------------------
0413 | 02 | RAM Installed (kb)
-----+----+---------------------------------------------------------------------
0415 | 02 | BOOT error flags
-----+----+---------------------------------------------------------------------
0417 | 02 | KEYBOARD Status		   76543210 76543210
	|	|   Insert		    80  x....... ........
	|	|   Caps Lock		    40  .x...... ........
	|	|   Num Lock		    20  ..x..... ........
	|	|   Scroll Lock	    10  ...x.... ........
	|	|   Alt shift		    08  ....x... ........
	|	|   Ctrl shift 	    04  .....x.. ........
	|	|   Shift (left)	    02  ......x. ........
	|	|   Shift (right)	    01  .......x ........
	|	|   Insert		    80  ........ x.......
	|	|   Caps Lock		    40  ........ .x......
	|	|   Num Lock		    20  ........ ..x.....
	|	|   Scroll Lock	    10  ........ ...x....
	|	|   Ctrl Num Lock	    08  ........ ....x... (hold state)
	|	|   Not used		    04  ........ .....xxx
-----+----+---------------------------------------------------------------------
0419 | 01 | KEYBOARD Alternate (reserved)
-----+----+---------------------------------------------------------------------
041A | 02 | KEYBOARD Buffer Head
041C | 02 | KEYBOARD Buffer Tail
041E | 20 | KEYBOARD 16-key Circular Buffer
-----+----+---------------------------------------------------------------------
043E | 01 | DISKETTE Recalibrate bits 0-3
043F | 01 | DISKETTE Motor bits 0-3
0440 | 01 | DISKETTE Motor count
0441 | 01 | DISKETTE Error status
0442 | 07 | DISKETTE Controller status
-----+----+---------------------------------------------------------------------
0449 | 01 | VIDEO CGA/MDA display mode				    Pages  Chars  Pixels
	|	|   00 = CGA  2-color (EGA 16-color) A/N text	 8	 40x25  320x200
	|	|   01 = CGA 16-color A/N text				 8	 40x25  320x200
	|	|   02 = CGA  2-color (EGA 16-color) A/N text	4/8	 80x25  640x200
	|	|   03 = CGA 16-color A/N text				4/8	 80x25  640x200
	|	|   04 = CGA  4-color graphics				 1	 40x25  320x200
	|	|   05 = CGA  2-color (EGA  4-color) graphics	 1	 40x25  320x200
	|	|   06 = CGA  2-color graphics				 1	 80x25  640x200
	|	|   07 = MDA  2-color (EGA  4-color) graphics	 4	 80x25  720x350
	|	|   08 = CGA  16-color graphics (undocumented)	 ?		   160x200
	|	|   09 = CGA  16-color graphics (undocumented)	 ?		   320x200
	|	|   0A = PC-JR
	|	|   0B
	|	|   0C
	|	|   0D
	|	|   0E
	|	|   0F
-----+----+---------------------------------------------------------------------

PC Compatible Low-Memory Map								PGS -- Page   5

ROM BIOS Data Area Map (0400-04EF)
----------------------------------

Addr | Ln | Function
-----+----+---------------------------------------------------------------------
0449 | 01 | VIDEO EGA display modes -		   CRT  Seg   Pages  Chars  Pixels
	|	|   00 = 16/64-color 8x14 text	   EGA  B800	 8	 40x25  320x350
	|	|   01 = 16/64-color 8x14 text	   EGA  B800	 8	 40x25  320x350
	|	|   02 = 16/64-color 8x14 text	   EGA  B800	4/8	 80x25  640x350
	|	|   03 = 16/64-color 8x14 text	   EGA  B800	4/8	 80x25  640x350
	|	|   04 = 4-color graphics		   CGA  B800	 1	 40x25  320x200
	|	|   05 = 4-color graphics		   CGA  B800	 1	 40x25  320x200
	|	|   06 = 2-color graphics		   CGA  B800	 1	 80x25  640x200
	|	|   07 = 4-shade mono 9x14 text	   MDA  B000	4/8	 80x25  720x350
	|	|   08
	|	|   09
	|	|   0A = 4/16 or 16/64-color graphics EGA  A000	1/2	 80x25  640x350
	|	|   0B
	|	|   0C
	|	|   0D = 16-color graphics		   CGA  A000  2/4/8  40x25  320x200
	|	|   0E = 16-color graphics		   CGA  A000  1/2/4  80x25  640x200
	|	|   0F = 4-shade mono graphics	   MDA  A000	1/2	 80x25  640x350
	|	|   10 = 16/64-color graphics 	   EGA  A000  2/4/8  80x25  640x350
-----+----+---------------------------------------------------------------------
044A | 02 | VIDEO Screen-width in columns
044C | 02 | VIDEO Screen regeneration-length
044E | 02 | VIDEO Screen location offset (current page)
0450 | 10 | VIDEO Screen page 0-7 cursor locations as col:row bytes
0460 | 02 | VIDEO Screen cursor start:end row bytes
0462 | 01 | VIDEO Current screen page
0463 | 02 | VIDEO Video-controller port-address
0465 | 01 | VIDEO Current CRT mode
0466 | 01 | VIDEO Color-palette mask
-----+----+---------------------------------------------------------------------
0467 | 05 | BOOT Work area
-----+----+---------------------------------------------------------------------
046C | 04 | CLOCK Master-count DWORD
0470 | 01 | CLOCK Roll-over flag
-----+----+---------------------------------------------------------------------
0471 | 01 | CTRL-BREAK flag (bit 7)
-----+----+---------------------------------------------------------------------
0472 | 02 | KEYBOARD Reset (1234) on Ctrl-Alt-Del
-----+----+---------------------------------------------------------------------
0474 | 01 | 286 Fixed disk status
0475 | 01 | 286 Fixed disk drive number
0476 | 01 | 286 Fixed disk control byte
0477 | 01 | 286 Fixed disk port offset
-----+----+---------------------------------------------------------------------
0478 | 05 | 286 Parallel-port timeout
047C | 05 | 286 Serial-port timeout
-----+----+---------------------------------------------------------------------
0480 | 04 | 286 Additional keyboard buffer
-----+----+---------------------------------------------------------------------
0484 | 01 | VIDEO EGA Screen rows
0485 | 02 | VIDEO EGA Bytes per character
0487 | 02 | VIDEO EGA Information	    76543210 76543210
	|	|   Clear/not-clear regen 80 x....... ........
	|	|   Onboard RAM		 60 .xx..... ........ 00=064k, 01=128k,
	|	|   Enhanced Keyboard	 10 ...x.... ........ 10=192k, 11=256k
	|	|   Not active monitor	 08 ....x... ........
	|	|   Wait for enable 	 04 .....x.. ........
	|	|   Monochrome attached	 02 ......x. ........
	|	|   Not emulate active	 01 .......x ........
	|	|   Feature bits		 F0 ........ xxxx....
	|	|   Switch settings 	 0F ........ ....xxxx
-----+----+---------------------------------------------------------------------
0489 | 03 | Reserved
-----+----+---------------------------------------------------------------------
048B | 01 | 286 Last diskette data rate selected
-----+----+---------------------------------------------------------------------

PC Compatible Low-Memory Map								PGS -- Page   6

ROM BIOS Data Area Map (0400-04EF)
----------------------------------

Addr | Ln | Function
-----+----+---------------------------------------------------------------------
048C | 01 | 286 Fixed-disk status-register
048D | 01 | 286 Fixed-disk error-register
048E | 01 | 286 Fixed-disk interrupt-flag
-----+----+---------------------------------------------------------------------
048F | 01 | 286 Fixed-disk/diskette combination controller flag
-----+----+---------------------------------------------------------------------
0490 | 01 | 286 Diskette drive 0 media state
0491 | 01 | 286 Diskette drive 1 media state
0492 | 01 | 286 Diskette drive 0 operation start state
0493 | 01 | 286 Diskette drive 1 operation start state
0494 | 01 | 286 Diskette drive 0 present cylinder
0495 | 01 | 286 Diskette drive 1 present cylinder
-----+----+---------------------------------------------------------------------
0496 | 01 | 286 Reserved
-----+----+---------------------------------------------------------------------
0497 | 01 | 286 Additional keyboard LED flag
-----+----+---------------------------------------------------------------------
0498 | 04 | 286 Real-time-clock user wait flag offset:segment
049C | 04 | 286 Real-time-clock user wait flag
04A0 | 02 | 286 Real-time-clock wait-active flag
-----+----+---------------------------------------------------------------------
04A2 | 06 | Reserved
-----+----+---------------------------------------------------------------------
04A8 | 04 | EGA DWORD pointer-save
-----+----+---------------------------------------------------------------------
04AC | 44 | Reserved
-----+----+---------------------------------------------------------------------

Interapplication Control Area (ICA) (04F0 - 04FF)
-----------------------------

DOS / ROM BASIC Control Area (0500 - 05FF)
----------------------------
Addr | Ln | Function
-----+----+---------------------------------------------------------------------
0500 | 01 | DOS Print-screen control (00 = Ok, 01 = in process, FF = error)
-----+----+---------------------------------------------------------------------
0501 | 03 |
-----+----+---------------------------------------------------------------------
0504 | 01 | DOS Single-diskette drive code (00 = drive A, 01 = drive B)
-----+----+---------------------------------------------------------------------
0505 | 0B |
-----+----+---------------------------------------------------------------------
0510 | 02 | BASIC default data segment
0512 | 04 | BASIC clock-tick interrupt-vector
0516 | 04 | BASIC break-key interrupt-vector
051A | 04 | BASIC diskette-error interrupt-vector
051E | E2 | BASIC Reserved
-----+----+---------------------------------------------------------------------
