'DIM ABSOLUTE an integer array over the BIOS Data Area, and with the
 'following list of constants, the entire BDA becomes a simple set of memory
 'variables which you can read and set as easy as a=b.

 'BIOS Data Area  (PC Memory Map)

 ' The first 512 ints represent the int vector table
 ' The next 128 ints represent the stack area used during post and bootstrap
 ' which should now be free to use for whatever we want

 %COM1Addr = &H200
 %COM2Addr = &H201
 %COM3Addr = &H202
 %COM4Addr = &H203
 %LPT1Addr = &H204
 %LPT2Addr = &H205
 %LPT3Addr = &H206
 %LPT4Addr = &H207  ' except PS2
 %Equipment   = &H208  ' 2 bytes  Equipment list flags (see also INT 11)
 '
 '     ³7³6³5³4³3³2³1³0³ 40:10 (value in INT 11 register AL)
 '      ³ ³ ³ ³ ³ ³ ³ ÀÄ IPL diskette installed
 '      ³ ³ ³ ³ ³ ³ ÀÄÄ math coprocessor
 '      ³ ³ ³ ³ ÃÄÅÄÄÄ old PC system board RAM < 256K
 '      ³ ³ ³ ³ ³ ÀÄÄ pointing device installed (PS2)
 '      ³ ³ ³ ³ ÀÄÄÄ not used on PS2
 '      ³ ³ ÀÄÁÄÄÄÄ initial video mode
 '      ÀÄÁÄÄÄÄÄÄÄ # of diskette drives, less 1
 '
 '     ³7³6³5³4³3³2³1³0³ 40:11  (value in INT 11 register AH)
 '      ³ ³ ³ ³ ³ ³ ³ ÀÄ 0 if DMA installed
 '      ³ ³ ³ ³ ÀÄÁÄÁÄÄ number of serial ports
 '      ³ ³ ³ ÀÄÄÄÄÄÄÄ game adapter
 '      ³ ³ ÀÄÄÄÄÄÄÄÄ not used, internal modem (PS2)
 '      ÀÄÁÄÄÄÄÄÄÄÄÄ number of printer ports
 '
 %MemoryKbytes = &H209  ' Memory size in Kbytes  (see INT 12)
 %KbdFlags1 = &H20B  ' (LSB only) Kbd flag byte 0 (see also KB FLAGS)
 '
 '     ³7³6³5³4³3³2³1³0³ Kbd flag byte 0
 '      ³ ³ ³ ³ ³ ³ ³ ÀÄÄÄ right shift key down
 '      ³ ³ ³ ³ ³ ³ ÀÄÄÄÄ left shift key down
 '      ³ ³ ³ ³ ³ ÀÄÄÄÄÄ CTRL key down
 '      ³ ³ ³ ³ ÀÄÄÄÄÄÄ ALT key down
 '      ³ ³ ³ ÀÄÄÄÄÄÄÄ scroll-lock is on
 '      ³ ³ ÀÄÄÄÄÄÄÄÄ num-lock is on
 '      ³ ÀÄÄÄÄÄÄÄÄÄ caps-lock is on
 '      ÀÄÄÄÄÄÄÄÄÄÄ insert is on
 '
 %KbdFlags2 = &H20C   ' (MSB only) Kbd flag byte 1 (see also KB FLAGS)
 '
 '     ³7³6³5³4³3³2³1³0³ Kbd flag byte
 '      ³ ³ ³ ³ ³ ³ ³ ÀÄÄÄ left CTRL key down
 '      ³ ³ ³ ³ ³ ³ ÀÄÄÄÄ left ALT key down
 '      ³ ³ ³ ³ ³ ÀÄÄÄÄÄ system key down and held
 '      ³ ³ ³ ³ ÀÄÄÄÄÄÄ suspend key has been toggled
 '      ³ ³ ³ ÀÄÄÄÄÄÄÄ scroll lock key is down
 '      ³ ³ ÀÄÄÄÄÄÄÄÄ num-lock key is down
 '      ³ ÀÄÄÄÄÄÄÄÄÄ caps-lock key is down
 '      ÀÄÄÄÄÄÄÄÄÄÄ insert key is down
 '
 %KeyBufHead = &H20D '  Offset from 40:00 to Kbd buffer head
 %KeyBufTail = &H20E '  Offset from 40:00 to Kbd buffer tail

 ' 40:1E  32bytes  Kbd buffer (circular queue buffer)

 %DriveStat = &H21F  ' (MSB) Drive recal status
 '
 '     ³7³6³5³4³3³2³1³0³ drive recalibration status
 '      ³ ³ ³ ³ ³ ³ ³ ÀÄÄ 1=recalibrate drive 0
 '      ³ ³ ³ ³ ³ ³ ÀÄÄÄ 1=recalibrate drive 1
 '      ³ ³ ³ ³ ³ ÀÄÄÄÄ 1=recalibrate drive 2
 '      ³ ³ ³ ³ ÀÄÄÄÄÄ 1=recalibrate drive 3
 '      ³ ÀÄÁÄÁÄÄÄÄÄÄ unused
 '      ÀÄÄÄÄÄÄÄÄÄÄÄ 1=working int flag
 '
 '  %DriveStat (LSB) Diskette motor status
 '
 '     ³7³6³5³4³3³2³1³0³ diskette motor status
 '      ³ ³ ³ ³ ³ ³ ³ ÀÄÄ 1=drive 0 motor on
 '      ³ ³ ³ ³ ³ ³ ÀÄÄÄ 1=drive 1 motor on
 '      ³ ³ ³ ³ ³ ÀÄÄÄÄ 1=drive 2 motor on
 '      ³ ³ ³ ³ ÀÄÄÄÄÄ 1=drive 3 motor on
 '      ³ ÀÄÁÄÁÄÄÄÄÄÄ unused
 '      ÀÄÄÄÄÄÄÄÄÄÄÄ 1=write operation
 '
 %DiskOps = &H220  ' (MSB) Motor shutoff counter (decremented by INT 8)
                   ' How many tics before drive motor shuts off
                   ' (LSB) Status of last diskette operation

 '     ³7³6³5³4³3³2³1³0³ status of last diskette operation
 '      ³ ³ ³ ³ ³ ³ ³ ÀÄÄÄ invalid diskette command
 '      ³ ³ ³ ³ ³ ³ ÀÄÄÄÄ diskette Addr mark not found
 '      ³ ³ ³ ³ ³ ÀÄÄÄÄÄ sector not found
 '      ³ ³ ³ ³ ÀÄÄÄÄÄÄ diskette DMA error
 '      ³ ³ ³ ÀÄÄÄÄÄÄÄ CRC check / data error
 '      ³ ³ ÀÄÄÄÄÄÄÄÄ diskette controller failure
 '      ³ ÀÄÄÄÄÄÄÄÄÄ seek to track failed
 '      ÀÄÄÄÄÄÄÄÄÄÄ diskette time-out

 %VideoMode    = &H224 ' (LSB) current video mode
 %ScreenCols   = &H225 ' Number of screen columns
 %VidRegenSize = &H226 ' Size of current video regen buffer in bytes
 %OffVidPageRB = &H227 ' Offset of current video page in video regen buffer
 %CursorPos0   = &H228 ' Cursor pos of pg 0, MSB=Row/LSB=Col
 %CursorPos1   = &H229 ' Cursor pos of pg 1, MSB=Row/LSB=Col
 %CursorPos2   = &H22A ' Cursor pos of pg 2, MSB=Row/LSB=Col
 %CursorPos3   = &H22B ' Cursor pos of pg 3, MSB=Row/LSB=Col
 %CursorPos4   = &H22C ' Cursor pos of pg 4, MSB=Row/LSB=Col
 %CursorPos5   = &H22D ' Cursor pos of pg 5, MSB=Row/LSB=Col
 %CursorPos6   = &H22E ' Cursor pos of pg 6, MSB=Row/LSB=Col
 %CursorPos7   = &H22F ' Cursor pos of pg 7, MSB=Row/LSB=Col
 %CursorSize   = &H230 ' (MSB) Cursor ending (bottom) scan line
                       ' (don't change directly)
                       ' (LSB) Cursor starting (top) scan line
                       ' (don't change directly)
 %DisplayPage  = &H231 ' (MSB) on display page number
 %CRTBaseAddr  = &H232 ' (MSB) Base Addr for on 6845 CRT controller
                       ' (B4h=3B4h=mono), (D4h=3D4h=color)
                       ' this is lsb, MSB is actually the LSB of %displaypage
 %CRTControlReg= &H232 ' (LSB) 6845 CRT mode control register value
                       ' (port 3x8h) EGA/VGA values emulate those of MDA/CGA
 %CGAPalette   = &H233 ' CGA current color palette mask setting (port 3d9h)
                       ' EGA and VGA values emulate the CGA
 %TimerCounter = &H236 ' Daily timer counter, equal to zero at midnight;
                        ' incremented by INT 8; read/set by INT 1A
 %ClockBreakFlags=&H238 ' (MSB) = Clock rollover flag, set when TimerCounter
                        ' exceeds 24 hours
                        ' (LSB) Break Flag, Bit 7 is set if CONTROL-BREAK
                        ' has EVER been hit (I guess you can reset it)
 %RebootFlag    = &H239 ' Soft reset flag via Ctl-Alt-Del or JMP FFFF:0
 '               1234h  Bypass memory tests & CRT initialization
 '               4321h  Preserve memory
 '               5678h  System suspend
 '               9ABCh  Manufacturer test
 '               ABCDh  Convertible POST loop
 %HDStatus    = &H23A ' (MSB) Status of last hard disk operation (see %DiskOps)
                      ' (LSB) Number of hard disks attached
 %LPT12TimeOut= &H23C ' (MSB) Timeout in secs for LPT1 (you can set it)
                      ' (LSB) Timeout in secs for LPT2
 %LPT34TimeOut= &H23D ' (MSB) Timeout in secs for LPT3 (you can set it)
                      ' (LSB) Timeout in secs for LPT4 (not PS/2)
 %COM12TimeOut= &H23E ' (MSB) Timeout in secs for COM1 (you can set it)
                      ' (LSB) Timeout in secs for COM2
 %COM34TimeOut= &H23F ' (MSB) Timeout in secs for COM3 (you can set it)
                      ' (LSB) Timeout in secs for COM4
 %KeyBufStart = &H240 ' Kbd buffer start offset (seg=40h)
 %KeyBufEnd   = &H241 ' Kbd buffer end offset (seg=40h)
 %ScreenRows  = &H242 ' (MSB) Rows on the screen (less 1, EGA+)
 %KBModeLED   = &H246 ' (MSB) Kbd mode/type
 '
 '     ³7³6³5³4³3³2³1³0³ Kbd mode/type
 '      ³ ³ ³ ³ ³ ³ ³ ÀÄÄÄ last code was the E1 hidden code
 '      ³ ³ ³ ³ ³ ³ ÀÄÄÄÄ last code was the E0 hidden code
 '      ³ ³ ³ ³ ³ ÀÄÄÄÄÄ right CTRL key down
 '      ³ ³ ³ ³ ÀÄÄÄÄÄÄ right ALT key down
 '      ³ ³ ³ ÀÄÄÄÄÄÄÄ 101/102 enhanced Kbd installed
 '      ³ ³ ÀÄÄÄÄÄÄÄÄ force num-lock if Rd ID & KBX
 '      ³ ÀÄÄÄÄÄÄÄÄÄ last char was first ID char
 '      ÀÄÄÄÄÄÄÄÄÄÄ read ID in process
 '
 ' (LSB) Kbd LED flags
 '
 '     ³7³6³5³4³3³2³1³0³ Kbd LED flags
 '      ³ ³ ³ ³ ³ ³ ³ ÀÄÄÄ scroll lock indicator
 '      ³ ³ ³ ³ ³ ³ ÀÄÄÄÄ num-lock indicator
 '      ³ ³ ³ ³ ³ ÀÄÄÄÄÄ caps-lock indicator
 '      ³ ³ ³ ³ ÀÄÄÄÄÄÄ circus system indicator
 '      ³ ³ ³ ÀÄÄÄÄÄÄÄ ACK received
 '      ³ ³ ÀÄÄÄÄÄÄÄÄ re-send received flag
 '      ³ ÀÄÄÄÄÄÄÄÄÄ mode indicator update
 '      ÀÄÄÄÄÄÄÄÄÄÄ Kbd transmit error flag
 '

 %KBLastScan = &H25D ' Scan code of last key (convertible)
 %DayCounter = &H25C ' Day counter (convertible and after)

 %ICAStart   = &H25E ' Intra-Applications Communications Area (16 bytes)
                     ' Useable data area, remains static between programs

 %PrtScrn    = &H280 ' Print screen status byte
                     ' 00 = PrtSc not on,
                     ' 01 = PrtSc in progress
                     ' FF = error

 %User26     = &H282 ' 26 Bytes more user area
                     ' officially categorized as
             ' 50:04  byte   DOS single diskette mode flag, 0=A:, 1=B:
             ' 50:05 10bytes POST work area
             ' 50:0F  byte   BASIC shell flag; set to 2 if current shell
             ' 50:10  word   BASICs default DS value (DEF SEG)
             ' 50:12  dword  pntr to BASIC INT 1Ch int handler
             ' 50:16  dword  pntr to BASIC INT 23h int handler
             ' 50:1A  dword  pntr to BASIC INT 24h disk error handler

 DIM ABSOLUTE BIOS(&H300) AS INTEGER AT 0
 COLOR 14,1:CLS:PRINT "BIOS Data Area Information."

 ? ,"COM1: " + HEX$(BIOS(%COM1Addr));
 ? ,"COM2: " + HEX$(BIOS(%COM2Addr));
 ? ,"COM3: " + HEX$(BIOS(%COM3Addr));
 ? ,"COM4: " + HEX$(BIOS(%COM4Addr))

 ? ,"LPT1: " + HEX$(BIOS(%LPT1Addr));
 ? ,"LPT2: " + HEX$(BIOS(%LPT2Addr));
 ? ,"LPT3: " + HEX$(BIOS(%LPT3Addr))
 ?
 ? ,"The current video mode is";BIOS(%VideoMode)\256
 ? ,"You are currently in" ; BIOS(%ScreenCols) ; "Column mode"
 ? ,"There are";(BIOS(%ScreenRows) AND 255)+1;"Rows on the screen"
 ? ,"The current display page is";BIOS(%DisplayPage) AND 255