remove docs

doc/bda.txt

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-The actual layout of the BDA is specific to the actual BIOS firmware running.
-This lists is focused on what a developer can reasonably rely on.
-
-0000 256 Interrupt vectors
-0300 256 bytes used as stack during POST
-0400 word: COM1 base I/O port
-0402 word: COM2
-0404 word: COM3
-0406 word: COM4
-0408 word: LPT1 base I/O port
-040A word: LPT2
-040C word: LPT3
-040E word: segment addr of the EBDA (rarely LPT4)
-0410 byte: equipment list flags (INT 11h, AL)
-     bit 0: IPL diskette installed
-     bit 1: math coprocessor present
-     bits 4-5: default VDU mode
-     bits 6-7: number of floppies minus one, 0 if none
-0411 byte: equipment list flags (INT 11h, AH)
-     bit 0: dma controller present
-     bits 1-3: number of serial ports
-     bit 4: game adapter present
-     bit 6-7: number of printer ports
-0413 word: memory size in kilobytes (INT 12h, AX)
-0417 byte: key toggle states
-     bit 0: right shift
-     bit 1: left shift
-     bit 2: ctrl
-     bit 3: alt
-     bit 4: scroll lock
-     bit 5: num lock
-     bit 6: caps lock
-     but 7: insert
-0418 byte: key pressed state (1 if currently held down)
-     bit 0: left ctrl key
-     bit 1: left alt key
-     bit 2: system key
-     bit 3: suspend key
-     bit 4: scroll lock
-     bit 5: num lock
-     bit 6: caps lock
-     bit 7: insert
-0419 byte: when typing a character by pressing the alt key and typing its code
-     into the numpad, this byte holds the current numeric value
-041A word: offset into the key ringbuffer, reading end
-041B word: offset into the key ringbuffer, writing end
-041E 16 words: key ringbuffer, holds place for 16 keypresses
-043E byte: drive restore flag
-043F byte: drive motor flag
-0440 byte: drive motor timeout counter in 1/18th seconds
-0441 byte: status of last disk operation
-0442 7 bytes: status buffer for FDC
-0449 byte: current VDU mode
-044A byte: number of visible display columns
-044C word: VDU display buffer size
-044E word: offset of current VDU page in buffer
-0450 8 words: 8 cursor positions for each VDU page (MSB=row, LSB=column)
-0460 byte: bottom scan line for cursor (dont write)
-0461 byte: top scan line for cursor (dont write)
-0462 byte: active display page number
-0463 word: VDU I/O address
-0465 byte: VDU mode control register
-0466 byte: VDU color select register
-0467 dword CS:IP for 80286 return from protected mode
-046C dword: time of the day in 1/18th second ticks
-0470 byte: rollover flag if above surpassed 24h (FFh = rollover)
-0471 byte: bit 7 is set on ctrl+numlock to indicate break condition
-0472 word: soft reset flag (set and JMP 0xFFFF:0)
-     1234: bypas memory tests and VDU setup
-     4321: preserve memory
-     5678: system suspend
-     9ABC: POST loop (on IBM convertible)
-0474 dword: reserved for hard disk bios
-0478 byte: LPT1 timeout in half seconds
-0479 byte: LPT2
-047A byte: LPT3
-047C byte: COM1 timeout in half seconds
-0480 word: key ringbuffer start (from 0x400)
-0482 word: key ringbuffer
-0500 byte: status of INT 5: print screen
-     00: no screen print in progress
-     01: in progress
-     FF: printer failure

doc/ega.txt

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-# Enhanced Graphics Adapter
-
-EGA is the successor of CGA, while itself being succeeded by VGA.
-
-## Detection
-
-mov ah, 12h
-mov bl, 10h
-int 0x10
-
-If there is an EGA (or up) display present, bl will be changed.