PEEK.COM
                            ========

Purpose:
--------

Allows the testing the value of any byte in low memory or any subset of bits
of any byte in a batch file by returning the requested byte or subset as
an ERRORLEVEL value.


Format for PEEK.COM:
--------------------

PEEK  xx:yy  [ AND zz ] [ comment ]

   "xx:yy" = address, hexadecimal  (segment:offset)
   "zz"    = optional bit mask, hexadecimal
   " comment " any text that can't be mistaken for the optional bit mask 
          -- must not start with "AND" if optional bit mask is omitted
          -- useful for documenting PEEK command without extra REM statement.

PEEK [comment]

   If the first item on the command-line is not a valid address then a short
   description of the command format is displayed.


Examples:
---------

PEEK 40:10 AND 02  test for math co-processor
IF ERRORLEVEL 2 GOTO OK
ECHO Sorry, a math co-processor is required for this programme.
GOTO DONE
:OK
mathprog
:DONE


In a batch file run from a RAM disk (otherwise you repeatedly access your 
disk drive until there is a keypress):


ECHO  Load mouse driver?  Press Alt for "no" and Ctrl for "yes".
KWAIT:
PEEK  40:17 AND 0C   check ALT and Ctrl key bits
IF ERRORLEVEL 8 GOTO CONT
IF NOT ERRORLEVEL 4 GOTO KWAIT
C:\DOS\mouse.com
:CONT


PEEK 40:49 check video mode
IF NOT ERRORLEVEL 8 IF ERRORLEVEL 7 GOTO MONOCHRM
colorprg
GOTO DONE
:MONOCHRM
monoprog
:DONE


Format for information below:
-----------------------------
PEEK  xxxx:yyyy   --   eee
or
PEEK  xxxx:yyyy AND zz  --  eee

                "xx:yy" = address, hexadecimal (0:0 to FFFF:FFFF)
                "zz"    = optional bit mask, hexadecimal (0 to FF)
                "eee"   = returned ERRORLEVEL, 0 to 255, decimal

Some Useful addresses for PEEK.COM:
-----------------------------------

PEEK  40:10  -- Equipment Word, low byte
PEEK  40:10  AND  C1  --   0 = no floppy drives
                           1 = 1 floppy drive
                          65 = 2 floppy drives
                         129 = 3 floppy drives (PC/XT only)
                         193 = 4 floppy drives (PC/XT only)
PEEK  40:10  AND  02  --   2 = math co-processor installed (else 0)
PEEK  40:10  AND  04  --   4 = mouse port on system board (AT only)
PEEK  40:10  AND  0C  --   0 = 16K motherboard RAM (PC/XT only)
                           4 = 32K motherboard RAM (PC/XT only)
                           8 = 48K motherboard RAM (PC/XT only)
                          12 = 64K motherboard RAM (PC/XT only)
PEEK  40:10  AND  30  --  initial video mode on boot-up:
                           0 = video adapter determines initial video mode (AT)
                          16 = colour, 40 columns by 25 rows (mode 1)
                          32 = colour, 80 columns by 25 rows (mode 3)
                          48 = monochrome, 80 columns by 25 rows (mode 7)

PEEK  40:11  -- Equipment Word, high byte
PEEK  40:11  AND 0E -- number of serial ports
                           0 = none
                           2 = 1 port
                           4 = 2 ports
                           6 = 3 ports
                           8 = 4 ports
PEEK  40:11  AND 10  --  16 = game port installed (else 0) (PC/XT only)
PEEK  40:11  AND 20  --  32 = internal modem (else 0) (some ATs only)
PEEK  40:11  AND C0  --  number of parallel printer ports
                          0 = none
                         64 = 1 port
                        128 = 2 ports
                        192 = 3 ports

PEEK  40:17  -- keyboard shift flags # 1
PEEK  40:17  AND  01  --   1 = Right Shift down (else 0)
PEEK  40:17  AND  02  --   2 = Left Shift down (else 0)
PEEK  40:17  AND  04  --   4 = Control key (left or right) down (else 0)
PEEK  40:17  AND  08  --   8 = Alt key down (left or right) (else 0)
PEEK  40:17  AND  10  --  16 = Scroll Lock on (else 0)
PEEK  40:17  AND  20  --  32 = Num Lock on (else 0)
PEEK  40:17  AND  40  --  64 = Caps Lock on (else 0)
PEEK  40:17  AND  80  -- 128 = Insert toggle on (else 0)

PEEK  40:18  -- keyboard shift flags # 2
PEEK  40:18  AND  01  --   1 = Left Ctrl down (101/102 keyboards only)
PEEK  40:18  AND  02  --   2 = Left Alt down (101/102 keyboards only)
PEEK  40:18  AND  04  --   4 = Sys Req key down (except 83-key keyboards)
PEEK  40:18  AND  08  --   8 = Pause enabled
PEEK  40:18  AND  10  --  16 = Scroll Lock key down
PEEK  40:18  AND  20  --  32 = Num Lock key down
PEEK  40:18  AND  40  --  64 = Caps Lock key down
PEEK  40:18  AND  80  -- 128 = Insert key down

PEEK  40:49  -- current video mode

PEEK  40:4A  -- number of character columns on the screen

PEEK  40:6C  -- low byte of timer-tick double word.  Makes a handy
                pseudo-random number generator if your sample rate is
                infrequent enough with enough unpredictable intervals between
                samples.

PEEK  40:70  -- midnight rollover flag (cleared on the next query to BIOS
                time routines)  0 = no rollover, 1 = rollover.

PEEK  40:75  -- number of hard drives

PEEK  40:84  -- (number of character rows on the screen) - 1

PEEK  50:00  -- Print Screen status
                  0 = print screen ready
                  1 = print screen in progress (or disabled by software)
                255 = error on last print screen

PEEK  F000:FFFE -- computer model byte (only approximate as some
                   companies didn't follow the IBM standard and some
                   other values may be possible with some other systems)
                255 = original PC
                254 = PC XT or Olivetti M240
                253 = PC jr
                252 = PC AT, PS/1, and some PS/2 models
                251 = PC XT with enhanced keyboard
                250 = PS/2 models 25 and 30; Olivetti M111
                249 = PC Convertable
                248 = most PS/2 models, Olivetti P500 and P800
                154 = Compaq XT/Compaq Plus
                 48 = Sperry PC
                 45 = Compaq PC/Compaq Deskpro

For more addresses and values, check out any good BIOS reference or 
Ralf Brown's Interrupt list.