When power is applied to the computer, the BIOS Data Area is created at memory location 0040:0000h with a typical size of 255 bytes.

Offset Hex	Offset Dec	BIOS Service	Field Size	Function
00h	0	Int 14h	2 bytes	Base I/O address for serial port 1 (communications port 1 - COM 1)
02h	2	Int 14h	2 bytes	Base I/O address for serial port 2 (communications port 2 - COM 2)
04h	4	Int 14h	2 bytes	Base I/O address for serial port 3 (communications port 3 - COM 3)
06h	6	Int 14h	2 bytes	Base I/O address for serial port 4 (communications port 4 - COM 4)
08h	8	Int 17h	2 bytes	Base I/O address for parallel port 1 (printer port 1 - LPT 1)
0Ah	10	Int 17h	2 bytes	Base I/O address for parallel port 2 (printer port 2 - LPT 2)
0Ch	12	Int 17h	2 bytes	Base I/O address for parallel port 3 (printer port 3 - LPT 3)
0Eh	14	POST	2 bytes	Base I/O address for parallel port 4 (printer port 4 - LPT 4) (Only found in PC/XT systems)
10h	16	Int 11h	2 bytes	Equipment Word
				Bits 15-14 indicate the number of parallel ports installed
				00b = 1 parallel port
				01b = 2 parallel ports
				03b = 3 parallel ports
				Bits 13-12 are reserved
				Bits 11-9 indicate the number of serial ports installed
				000b = none
				001b = 1 serial port
				002b = 2 serial ports
				003b = 3 serial ports
				004b = 4 serial ports
				Bit 8 is reserved
				Bit 7-6 indicate the number of floppy drives installed
				0b = 1 floppy drive
				1b = 2 floppy drives
				Bits 5-4 indicate the video mode
				00b = EGA or later
				01b = color 40x25
				10b = color 80x25
				11b = monochrome 80x25
				Bit 3 is reserved
				Bit 2 indicates if a PS/2 mouse is installed
				0b = not installed
				1b = installed
				Bit 1 indicated if a math coprocessor is installed
				0b = not installed
				1b = installed
				Bit 0 indicated if a boot floppy is installed
				0b = not installed
				1b = installed
12h	18	POST	1 byte	Interrupt flag - Manufacturing test
13h	19	Int 12h	2 bytes	Memory size in Kb
15h	21		2 bytes	Error codes for AT+; Adapter memory size for PC and XT
17h	22	Int 16h	1 byte	Keyboard shift flags 1
				Bit 7 indicates if Insert is on or off
				0b = Insert off
				1b = Insert on
				Bit 6 indicates if CapsLock is on or off
				0b = CapsLock off
				1b - CapsLock on
				Bit 5 indicates if NumLock is on or off
				0b = NumLock off
				1b = NumLock on
				Bit 4 indicates if ScrollLock is on or off
				0b = ScrollLock off
				1b = ScrollLock on
				Bit 3 indicates if the Alt key is up or down
				0b = Alt key is up
				1b = Alt key is down
				Bit 2 indicates if the Control key is up or down
				0b = Control key is up
				1b = Control key is down
				Bit 1 indicates if the Left Shift key is up or down
				0b = Left Shift key is up
				1b = Left Shift key is down
				Bit 0 indicates if the Right Shift key is up or down
				0b = Right Shift key is up
				1b = Right Shift key is down
18h	23	Int 16h	1 byte	Keyboard shift flags 2
				Bit 7 indicates if the Insert key is up or down
				0b = Insert key is up
				1b = Insert key is down
				Bit 6 indicates if the CapsLock key is up or down
				0b = CapsLock is key is up
				1b = CapsLock key is down
				Bit 5 indicates if the NumLock key is up or down
				0b = NumLock key is up
				1b = Numlock key is down
				Bit 4 indicates if the ScrollLock key is up or down
				0b = ScrollLock key is up
				1b = ScrollLock key is down
				Bit 3 indicates if the Pause key is active or inactive
				0b = pause key is inactive
				1b = Pause key is active
				Bit 2 indicates if the SysReg key is up or down
				0b = SysReg key is up
				1b = SysReg key is down
				Bit 1 indicates if the Left Alt key is up or down
				0b = Left Alt key is up
				1b = Left Alt key is down
				Bit 0 indicates if the Right Alt key is up or down
				0b = Right Alt key is up
				1b = Right Alt key is down
19h	24	Int 09h	1 byte	Alt Numpad work area
1Ah	26	Int 16h	2 bytes	Pointer to the address of the next character in the keyboard buffer
1Ch	28	Int 16h	2 bytes	Pointer to the address of the last character in he keyboard buffer
1Eh	60	Int 16h	32 bytes	Keyboard buffer
3Eh	61	Int 13h	1 byte	Floppy disk drive calibration status
				Bits 7-4 are reserved
				Bit 3 = floppy drive 3 (PC, XT)
				Bit 2 = floppy drive 2 (PC, XT)
				Bit 1 = floppy drive 1
				Bit 0 = floppy drive 0
				0b indicates not calibrated
				1b indicates calibrated
3Fh	62	Int 13h	1 byte	Floppy disk drive motor status
				Bit 7 indicates current operation
				0b = read or verify operation
				1b = write or format operation
				Bit 6 is not used
				Bit 5-4 indicates drive select
				00b = Drive 0
				01b = Drive 1
				10b = Drive 2 (PC, XT)
				11b = Drive 4 (PC, XT)
				Bit 3 indicates drive 3 motor
				0b = motor off
				1b = motor on
				Bit 2 indicates drive 2 motor
				0b = motor off
				1b = motor on
				Bit 1 indicates drive 0 motor
				0b = motor off
				1b = motor on
				0b = motor off
				1b = motor on
40h	63	Int 13h	1 byte	Floppy disk drive motor time-out
41h	64	Int 13h	1 byte	Floppy disk drive status
				Bit 7 indicates drive ready status
				0b = drive ready
				1b = drive not ready (time out)
				Bit 6 indicates seek status
				0b = no seek error detected
				1b = indicates a seek error was detected
				Bit 5 indicates floppy disk controller test
				0b = floppy disk controller passed
				1b = floppy disk controller failed
				Bit 4-0 error codes
				00000b = no errors
				00001b = illegal function requested
				00010b = address mark not found
				00011b = write protect error
				00100b = sector not found
				00110b = diskette change line active
				01000b = DMA overrun
				01001b = DMA boundary error
				01100b = unknown media type
				10000b = CRC error during read
42h	65	Int 13h	1 byte	Hard disk and floppy controller status register 0
				Bit 7-6 indicate the interrupt code
				00b = command completed normally
				01b = command terminated abnormally
				10b = abnormal termination, ready line on, or diskette changed
				11b = seek command not completed
				Bit 5 indicated seek command
				0b = seek command not completed
				1b = seek command completed
				Bit 4 indicated drive fault
				0b = no drive fault
				1b = drive fault
				Bit 3 indicates drive ready
				0b = drive ready
				1b = drive not ready
				Bit 2 indicates head state when interrupt occurred
				00b = drive 0
				01b = drive 1
				10b = drive 2 (PC, XT)
				11b = drive 3 (PC, XT)
				Bit 1-0 indicates drive select
				00b = drive 0
				01b = drive 1
				10b = drive 2 (PC, XT)
				11b = drive 3 (PC, XT)
43h	66	Int 13h	1 byte	Floppy drive controller status register 1
				Bit 7-0 indicates no error
				Bit 7, 1b = indicates attempted access beyond last cylinder
				Bit 6, 0b = not used
				Bit 5, 1b = CRC error during read
				Bit 4, 1b = DMA overrun
				Bit 3, 0b = not used
				Bit 2, 1b = Sector not found or reading diskette ID failed
				Bit 1, 1b = medium write protected
				Bit 0, 1b = missing address mark
44h	67	Int 13h	1 byte	Floppy drive controller status register 2
				Bit 7, 0b = not used
				Bit 6, 1b = deleted data address mark
				Bit 5, 1b = CRC error detected
				Bit 4, 1b = wrong cylinder
				Bit 3, 1b = condition of equal during verify
				Bit 2, 1b = sector not found during verify
				Bit 1, 1b = bad cylinder
				Bit 0, 1b = address mark not found during read
45h	68	Int 13h	1 byte	Floppy disk controller: cylinder number
46h	69	Int 13h	1 byte	Floppy disk controller: head number
47h	70	Int 13h	1 byte	Floppy disk controller: sector number
48h	71		1 byte	Floppy disk controller: number of byte written
49h	72	Int 10h	1 byte	Active video mode setting
4Ah	74	Int 10h	2 bytes	Number of textcolumns per row for the active video mode
4Ch	76	Int 10h	2 bytes	Size of active video in page bytes
4Eh	78	Int 10h	2 bytes	Offset address of the active video page relative to the start of video RAM
50h	80	Int 10h	2 bytes	Cursor position for video page 0
52h	82	Int 10h	2 bytes	Cursor position for video page 1
54h	84	Int 10h	2 bytes	Cursor position for video page 2
56h	86	Int 10h	2 bytes	Cursor position for video page 3
58h	88	Int 10h	2 bytes	Cursor position for video page 4
5Ah	90	Int 10h	2 bytes	Cursor position for video page 5
5Ch	92	Int 10h	2 bytes	Cursor position for video page 6
5Eh	94	Int 10h	2 bytes	Cursor position for video page 7
60h	96	Int 10h	2 bytes	Cursor shape
62h	97	Int 10h	1 byte	Active video page
63h	99	Int 10h	2 bytes	I/O port address for the video display adapter
65h	100	Int 10h	1 byte	Video display adapter internal mode register
				Bit 7, 0b = not used
				Bit 6, 0b = not used
				Bit 5
				0b = attribute bit controls background intensity
				1b = attribute bit controls blinking
				Bit 4, 1b = mode 6 graphics operation
				Bit 3 indicates video signal
				0b = video signal disabled
				1b = video signal enabled
				Bit 2 indicates color operation
				0b = color operation
				1b = monochrome operation
				Bit 1, 1b = mode 4/5 graphics operation
				Bit 0, 1b = mode 2/3 test operation
66h	101	Int 10h	1 byte	Color palette
				Bit 7, 0b = not used
				Bit 6, 0b = not used
				Bit 5 indicates mode 5 foreground colors
				0b = green/red/yellow
				1b = cyan/magenta/white
				Bit 4 indicates background color
				0b = normal background color
				1b = intensified background color
				Bit 3 indicates intensified border color (mode 2) and background color (mode 5)
				Bit 2 indicates red
				Bit 1 indicates green
				Bit 0 indicates blue
67h	103		2 bytes	Adapter ROM offset address
69h	106		2 bytes	Adapter ROM segment address
6Bh	107		1 byte	Last interrupt (not PC)
				Bit 7 indicates IRQ 7 hardware interrupt
				0b = did not occur
				01 = did occur
				Bit 6