










	   MMD - Mark's MegaDebugger.
	   ==========================


	   Version 1.00.  September 1994.


	   Copyright (c) 1993 Mark Thomas


	   NPS Software.

















    1 Contents
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	1	Contents
	2	Introduction
	2.1	Features and Limitations
	3	Legal Notice
	4	Quick Start
	5	Using MegaDebugger
	5.1	Using the Window Mode
	5.2	Using the Non-Window Modes
	5.3	Screen Swapping
	5.4	Expressions
	6	Debugging a Program
	6.1	Controlling Program Execution
	6.2	Restarting the Program
	7	Command Line Arguments
	8	Command Reference
	8.1	Command Parameters
	9	Configuration
	9.1	MMDCFG
	10	Default Key Definitions
	10.1	Default Microsoft Keys
	10.2	Default Borland Keys
	11	Operator Precedence Reference
	11.1	Assembler Language Operators
	11.2	C Language Operators
	11.3	Pascal Language Operators
	11.4	A86 Language Operators
	12	Error Messages
	12.1	Initialisation Errors
	12.2	Command Errors
	13	Known Bugs
	14	Registering
	15	Future Enhancements


    2 Introduction
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	MegaDebugger is a low level debugger for DOS programs that is
	designed to provide powerful debugging functions in a more
	modest amount of memory than traditional debuggers.

	This manual assumes that you have a basic knowledge of the 80x86
	processor's instruction set and registers and of the debugging
	process.  All key references in the manual are based on MMD's
	default Microsoft configuration, a configuration file MMD_TD.CFG
	is supplied for a Turbo Debugger setup.


    2.1 Features and Limitations

      þ Features:

	- A windowed output that automatically displays the registers,
	  watches and unassembly information.

	- Saves and restores MDA, CGA, EGA and VGA text and graphics
	  screens.  Register level swapping means that MMD can handle
	  split screens and VGA mode X perfectly.

	- Shows DOS memory allocation blocks, interrupt usage and open
	  files.

	- VGA 25, 28, 43, and 50 line text screen support.

	- Supports expressions using the operators and data types from C,
	  Pascal and Assembler/A86.

	- Extremely customisable.

	- Uses little memory (20k-80k) and works well on older 8086 and
	  286 systems with limited memory. Fast: No disk overlays and
	  quick conditional breakpoint and watchpoint evaluation.

	- MMD can 'keep' the keyboard interrupt, allowing it to function
	  with programs that install their own Int09 handler.

      þ Limitations:

	- No support for numeric co-processor data types.

	- No symbolic or source level debugging.

	- No 386 support.


    3 Legal Notice
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	The MegaDebugger documentation and software are not public
	domain.  They are copyrighted, Copyright (C) 1994 Mark Thomas.

	MegaDebugger is free for personal or private use.  However some
	contribution to the development of MMD would be appreciated.
	This can be a registration, donation, supply of information (see
	the final section) or simply postcard or Email saying that you
	find MMD useful.

	MegaDebugger is NOT free for use in a commercial, institutional
	or governmental setting.  Permission is given to use the
	software free of charge for a thirty day evaluation period,
	after which registration is required for continued use.  A
	single user registration costs AUS$50.00 and entitles you to a
	free upgrade to the next version of MMD.  For site licence
	information contact me.  Please send cheques or postal orders
	(in Australian dollars please) to:

	Mark Thomas
	8 Herronbee Street
	Toowoomba, Queensland
	Australia  4350.

	Please indicate a registration name and preferred disk size
	when registering.


	You are free to distribute COMPLETE and UNMODIFIED copies of all
	the software and documentation via any means to any recipient
	provided that no charge is made except a small and nominal fee
	whose sole purpose is to recover reasonable distribution
	expenses.

	This software is supplied "AS IS", WITHOUT ANY WARRANTY; without
	even the implied warranty of MERCHANTABILITY or FITNESS FOR A
	PARTICULAR PURPOSE.  It is supplied as is, in the hope that
	people will find it useful.  The author is not responsible for
	any damage caused by use or misuse of this software.


    4 Quick Start
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	If you are familiar with other debuggers such as DEBUG, SYMDEB,
	or CodeView then you will find the default MMD configuration
	provides a similar environment.  However MMD is designed to be
	configurable and MMD can easily be setup like Turbo Debugger
	using the sample configuration file supplied.

	Here is a quick introduction to using MMD:

	þ An important feature of MegaDebugger is its dual cursor
	system.  Only the Assembler and Command windows can be made
	active and both have separate cursors.	When the Assembler
	window is the current window then its cursor will be
	highlighted.  By holding the Shift key while using the scroll
	keys the other window cursor can be controlled.  All letters
	typed will go to the command window, and commands such as
	F9;Toggle Breakpoint will work regardless of which window is
	current.

      þ To change the size of the windows use Ctrl-G; Expand command
	window and Ctrl-T; Shrink command window.

      þ There are some useful shortcut keys for the Assembler Window:
	Ctrl+O;Origin, Ctrl+N;New CS:IP, Ctrl+P;NOP Instruction

      þ The commands used by MMD are a superset of those in DEBUG and
	are more flexible in that expressions can be used in the
	parameters.  The H command or F1;Help will provide help on their
	usage.	F3;Replay Command can be used recall and edit previous
	commands.

      þ "/VR /VG /VP"  provides the best screen swapping.

	Enables register level swapping, complete graphics saves and
	palette saves.	The default swapping mode MMD uses is the
	standard method used by most other programs which can corrupt
	graphic screens, while register level swapping can restore
	almost all screens.

    ³
    ³  Do NOT use register level swapping if the target program may use SVGA
    ³	screen modes.  All Super VGA modes are controlled by extended set of
    ³	chipset specific registers, which MMD's register level swapping is
    ³	not aware of.  Therefore when swapping between the target screen and
    ³	MMD only the standard VGA registers will be saved and restored,
    ³	leaving the extended registers in an undetermined state.
    ³
    ³  *** USING REGISTER LEVEL SWAPPING WITH SUPER VGA MODES MAY DAMAGE ***
    ³  *** YOUR MONITOR OR GRAPHICS CARD.				 ***
    ³
    ³  All other MMD swapping modes (Standard and VGA BIOS) are completely
    ³	safe to use in all screen modes.
    ³

      þ "/H- /VN /VR"  minimises the memory used by MMD.

	Disables help and higher screen mode changes and enables
	register level swapping.  The standard swapping mode uses about
	16k of memory for swapping, while register mode uses only 4k.
	Help uses around 15k of memory and is rather limited so should
	be disabled if it is not required.  If there is still
	insufficient conventional memory for the target to run then try
	Screen (/S) or DOS (/D) output modes (Note: is difficult to use
	LOADHI to load MMD into the HMA as about 128k of memory is used
	during initialisation).

      þ I also recommend using the A86 language support: it provides a
	unambiguous method for specifying decimal and hexadecimal numbers
	and has the same operators as TASM and MASM.

      þ MMDCFG can be used to create a custom configuration for MMD.


    5 Using MegaDebugger
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	When MegaDebugger has successfully loaded it will display its
	initial screen with a start up message and a hyphen (-) prompt.

	MegaDebugger.  Version 1.00
	(c) 1994 Mark Thomas
	CPU:80286
	-

	This means that the target program is ready for execution and
	that MegaDebugger is ready to accept your commands.  Each
	command consists command name of one or two characters followed
	by any parameters that are required.  All input on the command
	line is case insensitive, so input can be in upper or lower
	case.

    5.1 Using the Window Mode

	The default output mode for MegaDebugger is window mode.  This
	presents the debugging information on the screen in a series of
	windows.  This is the most powerful mode of operation because
	all the information from the Register, Unassembly and Watch
	commands is automatically displayed and updated on the screen at
	the same time.

      Register Windows

	There are two register windows in MegaDebugger, one across the
	very top of the screen known as the Horizontal Register window,
	which will be closed initially.  The second, the Vertical
	Register window, runs along the right hand side of the screen
	and is open by default (the initial settings can be changed with
	MMDCFG).  The reason for providing two windows is that the
	output in the command window, particularly that of Dump Memory
	command, can sometimes be obscured by the Vertical Register
	window.

	The Vertical Register can be open and closed with F2;Toggle
	Vertical Register Window, Ctrl-F2;Toggle Horizontal Register
	Window performs the same function for the Horizontal Register
	window.

      Watch Window

	The Watch window displays any watches that are active.	If there
	are no watches then it will be closed, and remain so until a
	watch is added using one of the Watch commands.  Each time a
	watch is added or deleted this window will resize itself to
	display all the current watches.

      Assembler Window

	In the centre of the screen is the Assembler window, which
	displays an area of memory in disassembled processor
	instructions.  A large blue highlight bar indicates the current
	address of CS:IP.  As each instruction is executed, and the
	values of CS:IP change the bar moves through the displayed code
	to represent the flow of execution.  Also in the window is a
	solid non-blinking cursor, which is the Assembler window cursor.

	An important feature of MegaDebugger is the dual cursor system.
	At any time there are two independent cursors on the screen, the
	first is the traditional hardware blinking cursor in the Command
	window.  The second is a simulated cursor in the Assembler
	window.  One of the windows is known as the current window, the
	window that responds to the scrolling keys (Up, Down, PgUp, and
	PgDn) and the other will be the secondary window.  MegaDebugger
	provides a way to access the secondary window without having to
	use F6;Change Window.

	By default the Assembler window is the current window.	Using
	any of the window scroll keys will scroll the Assembler window.
        By pressing and holding the Shift key while using the scroll
        keys the Command window cursor can be controlled.  This method
	is faster than continually pressing F6;Change Window to move
	between windows.  It also means that a breakpoint can be set at
	the address of the Assembler window cursor using the F9;Toggle
	Breakpoint key at any time regardless of which is the current
	window.

	The converse is also true, if the Command window is the
	current window then the scroll keys will move the Command
	window cursor and the Shift and scroll key combinations will
	address the Assembler window.

	When the Assembler window is made the current window then its
	cursor will become highlighted.  You can determine which is the
	current window simply by looking at the colour of the Assembler
	window cursor.

	Scrolling the Assembler window backwards will cause the screen
	to flip backwards.  This is because it is very difficult for MMD
	to determine the length of a previous instruction, as each byte
	may have a valid interpretation.  Because it is possible for the
	disassembly to become out of step with the actual code this way
	the offset address can be adjusted one byte at a time using the
	Ctrl-Right and Ctrl-Left keys.

      Command Window

	At the very bottom of the screen is the Command window, where
	the MegaDebugger user prompt (-) is displayed and your commands
	are entered.  The current input position is indicated by the
	blinking cursor.  This is where the characters you type will be
	displayed.  All keyboard input goes to this window regardless of
	which is the current window.  Previous commands can be recalled
	and edited using F3; Replay Command.

	The initial height of the window is only five lines. Any lines
	that are printed by MMD will force the top lines to scroll
	upward and disappear behind the Assembler window.  When the
	window scrolls up the blinking cursor will disappear from the
	screen, but it will still record any characters you enter.

	The height of the Command window (and consequently the Assembler
	window) can be changed using the Ctrl-G and Ctrl-T keys.

    5.2 Using the Non Window Modes

	When either Screen or DOS output mode is specified on the
	MegaDebugger command line the window functions are disabled and
	the output can be thought of as if the Command window has been
	expanded to fill the entire screen.  Instead of updating the
	register window after a section of the target program has been
	executed, MMD will dump the contents of the registers to the
	screen.

	The function keys will continue to work in Screen output mode,
	except those that are specifically for window mode.  In DOS
	output mode none of the function keys are available so the
	equivalent MegaDebugger commands must be used.

	Non window modes are usually only used to save memory or for a
	primitive form of remote debugging (by redirecting the DOS
	output to a COM port and displayed by a terminal program on the
	local computer).

    5.3 Screen Swapping

	Because MMD output occupies the entire screen in Window and
	Screen modes it leaves no space for the target program to
	display its output.  To overcome this, a technique called screen
	swapping is used to save and restore the output screen each time
	a section of the target screen executes.  This means that all
	the target program's output will be displayed normally on the
	screen, and when MMD becomes active it will save a copy of this
	screen and replace it with its own.  Then when returning to the
	target program the output screen is restored.  MMD has three
	swapping modes Smart, On and Off.  In most cases only smart
	swapping mode will be the only mode required.  It swaps the
	screen only when it considers necessary:

	- An instruction reads or writes to BIOS video data or screen
	  memory.

	- An IN or OUT (and INS or OUTS) instruction is executed.

	- During Go, Proceed or Goto Cursor.

	The "On" swapping mode swaps all the time, "Off" will disable
	all swapping (losing any target output and corrupting the MMD
	screen).  The View Output command or F4;View Output Screen can
	be used to view the output screen from MMD at any time.

    5.4 Expressions

	MegaDebugger can evaluate expressions using operators from one
	of four languages supported: C, Pascal, Assembler and A86. By
	default Assembler operators are used, but this can be modified
	as a command option or with MMDCFG.  An expression can be used
	in any command parameter instead of providing a constant
	address.

	An expression consists of an ordered mixture of constants and
	operators from the current language.

      þ Constants

	There are three types of constant values accepted by
	MegaDebugger:

	- Numeric Constants: Numbers are interpreted according to the
	  current radix and language.  MMD has a several extensions to
	  the standard radix types for some languages, this is detailed
	  in Section 11.

	- Registers: The name of any of processor registers, both 8 and
	  16 bit, can be specified in an expression.  MMD will determine
	  the current value of the register and use it in the
	  expression.

	- Quoted Character Constants: A single character enclosed in
	  single quotation marks (') will be used in the expression as
	  the ASCII character equivalent.  To specify a single quote as
	  the character constant use three consecutive quote characters
	  (''').

      þ Operators

	MMD supports all simple unary and binary operators and
	parentheses for each language, see Section 11.	It does not
	support any assignment operators, array and structure operators,
	or pointer and type casting operators.	In evaluating an
	expression all arithmetic is done in 16-bit unsigned integer
	math, if the result exceeds that which can be stored in 16 bits
	then it will simply wrap around to zero, with no warning.


    6 Debugging a Program
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

    6.1 Controlling Program Execution

	MegaDebugger provides a number of ways for you to control the
	execution of the target program.

      Trace.

	In single step mode, control returns to MMD after each processor
	instruction is executed.  The Trace command or F8;Trace function
	key can be used to trace through the target program.

      Breakpoint.

	A breakpoint defines an address in memory which, when executed,
	will return control to MMD.  MegaDebugger provides 10 user
	breakpoints for this purpose.  Breakpoints can be set with the
	Set Breakpoint command, F9;Toggle Breakpoint function key or
	with the Go command.

      Proceed.

	Proceed is similar to the trace function however it will step
	over LOOP, CALL and repeated string instructions.  The Proceed
	command or F10;Proceed function key can be used to proceed
	through the target program.

      Go.

	When the Go function is used the target program is allowed to
	execute freely until it terminates, or is interrupted by a
	breakpoint or keyboard break.  The Go command or the F5;Go
	function key can be used to run the target program.

      Keyboard Break Interrupt.

	When the target program is running MMD will monitor the keyboard
	for the Ctrl-Break keyboard combination.  When these keys are
	pressed it will force an immediate entry into the debugger
	screen.  This method is different to the normal DOS Ctrl-Break
	routine, however if you wish to force a DOS break then use the
	Ctrl-C key combination.  MMD will not normally interrupt DOS
	while it is handling a software INT 21 instruction, instead MMD
	will wait until DOS completes processing and the break will
	occur immediately after the INT 21 instruction.

      WatchPoint (Global Breakpoint)

	Setting a watchpoint and executing the target will cause MMD to
	single step through each instruction and evaluate the expression
	for each watchpoint at each step.  If the result is TRUE then
	MMD will interrupt execution.  This slows the execution speed
	greatly.

      Go To Cursor.

	When using Window mode there is an additional way to run the
	target program, F7; Go To Cursor.  This will place a temporary
	breakpoint at the address represented by the current cursor
	position in the Assembler window and then run the target program
	using the Go command.


    6.2 Examining and Modifying the Program State

	Each time MMD returns from executing a section of the target
	program it will update the display of the program state and
	display the prompt to allow debugger commands to be entered.
	The program can be altered at this stage by changing the values
	of flags and registers (including CS:IP), or by modifying the
	program memory with the Enter or Fill memory commands.

    6.3 Restarting the Program

	When the target program runs to completion MegaDebugger will
	display the program termination messages:

	Program Terminated Normally (xx)

	    or

	Program Terminated Resident (xx)

	The value in brackets is the return code, or error level that
	the target program returned.  No further instructions can be
	executed by MMD until the target program is reloaded using the
	Reload Target File command.  If you try to use one of the
	execution commands (Go, Trace or Proceed) or their equivalent
	function keys MMD will display a message advising you of this:

	Program Terminated: Restart


    7 Command Line Arguments
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	The command line format for MegaDebugger is:

	MMD [options] [target [arguments]]

      þ options

      /?, /H  Command line help.

      /C<file> Use configuration file.

	Forces a specific configuration file to be loaded.  MMD will
	automatically load a configuration file called 'MMD.CFG' in the
	default directory, but other files with other names must be
	directly specified.

      /D      DOS redirectable output.

	Specifying DOS output mode will disable the screen swapping and
	use DOS functions for both input and output.  These DOS
	functions do not support function keys so all input will be
	through the command line.  The primary advantage of this mode is
	that the input and output of MMD can be redirected using the DOS
	redirection commands.  MMD uses around 10k less memory because
	the screen saving buffers are not required.

      /DO, /2 Dual Monitor output.

	Redirects all MMD output to the monochrome screen on a system
	with two monitors.

    ³	Untested: I did not have the necessary equipment to actually
    ³	try this out but have tested it as far as possible, could
    ³	someone let me know if they can use it with their system.

      /Hxx    Set screen height: 25,28,43,50.

	This switch is relevant only for EGA and VGA systems, where the
	number of lines in a text screen can be varied.  By default
	MegaDebugger will use the same number of screen lines that the
	current text screen has, but this switch allows you to override
	this and use a specific screen size.

	Increasing the size of the screen also increases the size of the
	buffer required by MegaDebugger for screen swapping.  You can
	view the difference by examining the size of the debugger memory
	block with the Memory Information command.

	In DOS output mode this switch has no effect.

      /H[ñ]   Include or exclude online help.

	Disables loading of the MMD help file.	Although compressed is
	still quite large and this option allows loading of the help
	file to be disabled, decreasing the amount of memory required by
	MMD.  Help will still be available through the command line
	?;Help command.

      /I[ñ]   Allow DOS process ID switching.

	MMD attempts to have as little to do with DOS as possible,
	however when writing files from MMD it is wise (though not
	necessary) to enable PSP switching.

    ³	 Note: MMD does not have a critical error handler so any
    ³	 any errors occurring when writing a file with
    ³	 or W will be passed to the target's handler, if it has one.

      /KD[ñ]  Keep keyboard interrupt thru DOS.

	Many programs install a new keyboard interrupt (Int09) meaning
	that the MMD keyboard handler cannot interrupt the target
	program.  MMD will attempt to 'keep' the keyboard interrupt by
	intercepting any DOS Set Interrupt Vector (Int21/AH=25h) calls
	that would change the Int09 vector and installs its own handler
	which chains to the requested new handler.

      /KP[xx][ñ] Keep keyboard interrupt thru PIC.

	This option attempts to keep the keyboard by reprogramming the
	Programmable Interrupt Controller (PIC) to generate an interrupt
	other than Int09 when a key is pressed.  A program installing a
	new handler for interrupt 09h will be unaware that MMD is using
	a different set of interrupts.	As MMD controls these new
	interrupts it can check for a keyboard break before chaining to
	the target's Int09 handler.  This method ensures that a
	keyboard break can always be detected as long as the keyboard
	IRQ is enabled.  However reprogramming the PIC has two
	drawbacks, firstly a series of 8 consecutive interrupts must be
	available for the new interrupts.  In most systems there is
	usually such a range between interrupts 78h - EFh.  The default
	interrupt range is D8h-DFh, but MMDCFG should be used to verify
	that this or any other range is free before it is used.  The
	second problem is that redirecting the interrupts may interfere
	with a protected mode environment which has usually already
	shifted the interrupts.  If VCPI or DPMI is detected then MMD
	will notify them of the change.

      /Kx     Key definitions; B:Borland, M:Microsoft.

	By default MegaDebugger uses CodeView key definitions, but if
	you are more familiar with Turbo Debugger or any of the Borland
	Integrated Development Environments then this switch will
	redefine the function keys (although there are some differences
	between individual Borland and Microsoft products, see Section
	10 for MMD key definitions).

      /S      Screen swapping, no windows.

	This switch will disable the Window output mode of MMD and
	produce line orientated output similar to the DOS output mode.
	However screen swapping and function keys will still be active.
	This conserves memory by not having to load the window code and
	buffers.

      /Lx     Expression language; A:Assembler, P:Pascal, C:C, 8:A86.

	MegaDebugger supports expression operators from four different
	languages: C, Pascal, Assembler and A86.  By default Assembler
	operators will be used.

      /Vx     Screen swapping type; S:Standard, B:VGABIOS, R:Register.

	Sets the method MMD uses for swapping screens.	Standard mode
	uses several BIOS functions and adaptor registers to swap
	screens.  VGABIOS mode uses the VGA BIOS Save and Restore state
	functions, it was written only out of curiosity and was
	extremely slow on my system.  Register level is the most
	powerful method, it swaps modes by reading and writing all the
	registers directly, so can support mode-x and split screens but
	not SVGA modes.  Register level swapping is supported on MDA,
	CGA and VGA systems.

    ³
    ³  Do NOT use register level swapping if the target program may use SVGA
    ³	screen modes.  All SuperVGA modes are controlled by extended set of
    ³	chipset specific registers, which MMD's register level swapping is
    ³	not aware of.  Therefore when swapping between the target screen and
    ³	MMD only the standard VGA registers will be saved and restored,
    ³	leaving the extended registers in an undetermined state.
    ³
    ³  *** USING REGISTER LEVEL SWAPPING WITH SVGA MODES MAY DAMAGE YOUR ***
    ³  *** MONITOR OR GRAPHICS CARD.					 ***
    ³
    ³  All other MMD swapping modes (Standard and VGA BIOS) are completely
    ³	safe to use in all screen modes.
    ³

      /VG[ñ]  Enable complete EGA/VGA graphics save.

	By default MMD will not save and restore video memory used for
	the character set.  In standard text modes and some graphics
	modes this is acceptable but in graphics modes and some custom
	text modes it will corrupt the screen.	Enabling a complete
	graphics save requires 4k more memory.

      /VN[ñ]  Disable higher mode sets.

	MMD can allow its screen height to be changed from the command
	prompt, however this requires additional buffers to save the
	largest screen size possible, even if it is not used.

      /VP[ñ]  Enable VGA palette saving.

	MMD saves and restores the palette information.  Uses about 1k
	extra memory.

      þ target

	This specifies the name of the file you wish to debug.	An
	extension is not required for the file name if the file is .COM
	or .EXE type because MMD will try both extensions when searching
	for the target file.  The first attempt will be for a .COM
	extension and then .EXE, which is the same order that DOS
	searches for an executable file.  In window mode the file name
	and path of the target file are displayed at the top of the
	screen.  MMD does not allow the target file to be changed once
	it is loaded.

      þ arguments

	This is the command line you wish to run the target program with
	when MegaDebugger loads it.  The command line can be changed
	with L;Reload Target command.


    8 Command Reference
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

      Command Parameters

	- Address: An address can consist of just an offset, in which
	  case the command will use a default value (either DS or CS
	  depending on which command) for the segment, or both the
	  segment and offset values.  In this case the segment and
	  offset must be separated by the segment override character (a
	  colon ':').

	- Byte: A byte value is an 8-bit expression.

	- Command line: The command line is simply a string of
	  characters which will be passed to the target program as its
	  command line argument.

	- Comment: A comment string is simply a string of characters.

	- Count: A count is simply a expression that will evaluate to a
	  word.

	- Expression: An expression can be supplied as defined in the
	  Expressions section, however the segment override operator is
	  also allowed.

	- Format: A format character defines how the output of the
	  command is to be displayed.  MegaDebugger uses the following
	  format characters:

	     A	  ASCII string
	     B	  Byte
	     C	  Character
	     D	  Double Word
	     I	  Decimal integer
	     L	  Long Integer
	     U	  Unsigned decimal integer
	     W	  Word

	- List: A list is a set of numbers between 0 and 9, or * to
	  specify all numbers from 0-9.

	- Port: A port address is the number of one of 65,355 I/O ports
	  available on PC computers.

	- Range: A range consists of two addresses, or a single address
	  and a length specifier.  Only the first address may have a
	  segment specified.  In some commands the range is optional and
	  only the address may have to be supplied.  To specify an
	  entire segment in a range a length of 0 should be given.

	- Register: Any 16-bit register name, as well as the flags (FL)
	  register.

	- Values: A set of bytes and strings separated by spaces.  The
	  strings must be delimited by matching (') or (") characters.
	  To specify one of these characters as an element of the string
	  use either double delimiters 'it''s', or use the other type of
	  delimiter to delimit the string, "it's".  The ASCII values of
	  the characters in the string are used as byte values.

    Current Location
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    .

	This command will return the Assembler window highlight cursor
	bar, which represents the address of CS:IP, to the top of the
	screen.

      SeeAlso: Ctrl-O;Origin.


    Help
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    ?, H

	Displays a brief summary of all MMD commands and their
	parameters.  Unlike the help window this command is always
	available, in all output modes and when the context sensitive
	online help window is not included.

      SeeAlso: F1;Help.


    Evaluate Expression
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    ? expression[,format]

	This is essentially a calculator, any expression given will be
	evaluated and displayed.  The optional format character allows
	the result to be displayed in a format other than the default,
	which is a hexadecimal word.

      SeeAlso: Configuration;Default Expression Format.


    Assemble Instructions
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    A [address]

	Assembles instructions directly into memory. This is similar to
	the DEBUG assembler with the following enhancements:

	- Inline overrides are supported, eg: REP MOVSB and MOV
	  AL,ES:[SI].

	- Most real mode 286 instructions are available.

	- Directives ORG, DB and DW.

	The default segment is the current CS.

	Math coprocessor instructions are not supported.

      SeeAlso: Ctrl-P;NOP Instruction.


    Set a Breakpoint
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    BP [address] [count][,expression]

	MegaDebugger supports 10 user breakpoints.  These can be set at
	any address in memory, except that of another breakpoint.  If at
	any point the computer executes the instruction at the address
	of a breakpoint the program will be interrupted and MMD will
	regain control.

	If no address is specified then it will default to the current
	CS:IP.

	The optional count allows the breakpoint to be passed a number
	of times before it will interrupt the program's execution. This
	is particularly useful when the breakpoint is placed inside a
	loop. Each time the breakpoint is executed the pass count is
	decremented, until it reaches 1 when the breakpoint becomes the
	same as an ordinary breakpoint with no pass count.  The only way
	to clear a pass count is by manually clearing and resetting the
	breakpoint.

      SeeAlso: F9;Toggle Breakpoint.


    Clear Breakpoints
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    BC list

	Clearing a breakpoint will remove it from the list of
	breakpoints that MMD maintains and discards it.

	Multiple breakpoint numbers may be specified in the list
	parameter and all will be removed.

      SeeAlso: F9;Toggle Breakpoint.


    Disable Breakpoints
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    BD list

	Disabling a breakpoint removes their effect but still keeps them
	in the list of breakpoints.  This allows then to be reenabled at
	a later point, which is faster and more convenient then
	clearing and resetting a breakpoint.

	Disabled breakpoints will be displayed in the Breakpoint List
	command with the letter D beside its entry.  In the Assembler
	window a disabled breakpoint will be the same colour as the
	text, and not highlighted.


    Enable Breakpoints
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    BE list

	After having disabled a breakpoint you may reactivate it using
	this command.  Enabling a breakpoint that is already enabled
	will have no effect on that breakpoint.


    List all Breakpoints
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    BL

	The list of breakpoints displays the address, status, and pass
	count for all current breakpoints.

	The pass count is displayed as a decimal integer rather than a
	hexadecimal number.


    Compare Memory
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    C range address

	Compares all bytes in the range to those starting at address,
	and displays any of the differences.  For each difference found
	MMD will display the address and the bytes that differ.

	If the two areas are identical then there will be no display.


    Dump Memory
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    D[format] [range]

	Dumps memory in the range specified to the screen in the format
	specified.  If no range is specified then the dump will continue
	from the last address previously displayed.

	There should be no space between the command name and the format
	character, or the format will be interpreted as part of the
	range address.	The range should also be separated from the
	command name by a space, to prevent the address being
	interpreted as a format character.

	The character format, 'C' is not supported in the Dump Memory
	command, instead the byte format will display an ASCII character
	translation of each byte it displays.


    Enter
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    E address [values]

	This command enters bytes directly into the memory at address.

	If no values are specified then an interactive mode is started.
	In this mode you will be prompted with the current address and
	the current value for that byte.  You then have four choices:

	- Enter a new value for the byte

	- Press the space bar to advance to the next byte.

	- Press the minus (-) key to move back to the preceding address.

	- Press Enter which will terminate the interactive mode.


    Fill Memory
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    F range values

	Fills the memory within the range with the values specified.

	If the range is larger than the size of the values then the
	values will be repeated until they fill the range.  When the
	size if the range is smaller than the values then the values
	will be truncated to fill only the range specified.


    Go
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    G [address] {address}

	This command will execute the target program, which will
	continue to run until it terminates, executes a breakpoint or is
	interrupted by a keyboard break.

	If the address is specified then a breakpoint will be set at
	that address, which is in the current code segment by default.
	This breakpoint is only temporary, and is not added to the user
	breakpoint list, and it will be lost when the control returns to
	MMD.

      SeeAlso: F5;Run.


    Set Screen Height
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    H25, H28, H43, H50

	Sets the MMD screen height, if allowed by the video card and
	command line options.

      SeeAlso: /VN command line switch


    Input Byte from Port
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    I port

	This command will read the current value from the I/O port
	specified and displays it.


    Reload Target
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    L [arguments]

	Reloading the program will terminate the program that is
	currently executing and reload the target file from disk.  It
	will then be ready to start execution again from the beginning
	of the program.

	If no command line is specified then MMD will reuse the current
	command line.  To specify no command line type a single space
	character after the command name.


    Memory Information
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    M[ | A | I | H | V ]

	The output of this command is similar to the DOS MEM command.
	There are five options available:

	- The default is a list of all the system and program memory
	  blocks.  Environment blocks will not be displayed.

	- A All memory information will be displayed, including
	  interrupts and file information.

	- I Interrupt information will be displayed for the main memory
	  blocks.

	- H Provides information about any open files for program memory
	  blocks.

	- V Verbose mode displays all memory blocks.

	File information provides information about files opened with
	file handles (not FCBs) and relies on undocumented DOS
	structures to find the names of the files, and so it is
	sensitive to changes between DOS versions.


    Move Memory
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    M range address

	This command will copy the block of memory in the range to the
	destination address.

	If the blocks overlap then MMD will ensure that the move is
	performed without losing any of the data.


    Set Radix
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    N2, N8, N10, N16

       Changes the current radix for input values.

      SeeAlso: Configuration;Default Radix.


    Output Byte to Port
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    O port byte

	This command will output the byte value to the I/O port.


    Set Option
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    O[B | U][+ | -]

	Sets an option:

	- OB enables or disables byte decoding display in the Assembler
	  window.

	- OU toggles between upper and lower case display.

      SeeAlso: Configuration;Byte Decoding, Configuration;Unassembly Case.


    Proceed
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    P [count]

	The proceed command is similar to the trace command, however it
	will step over loops, calls and repeated string instructions.

	When the optional count is used then proceed will execute count
	number of times before returning to user input.  The debugger
	display will be updated for each instruction executed during the
	count.

	The proceed command will not work in ROM.

	The following instructions will be stepped over by this command:

	- CALL

	- LOOP, LOOPZ, LOOPNZ

	- REPx SCASx, REPx LODSx, REPx STOSx, REPx CMPSx, REPx MOVSx

	- REPx INSx, REPx OUTSx


    Quit
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    Q

	This command will terminate the target program, and quit from
	MegaDebugger to DOS.


    Register
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    R [register] [expression]

	The Register command allows you to set new values for any of the
	processor register and flags.

	If no expression is given for the register then MMD will display
	the current value and prompt you for a new one. You may enter a
	new value for the string or ignore it and leave the contents of
	the register unchanged by pressing Enter.

	If no parameters are supplied to this command then it will dump
	the current values for the registers to the screen.

	To modify the flags the FL register name should be given, again
	you may either specify the new value directly or be prompted
	with a display of the current flag settings.


    Search Memory
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    S range values

	Searches all the memory in the range for the sequence of values
	specified.  For each match MMD will display the address of that
	match.

	If the values are not found then there will be no display.


    Set Swapping Mode
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    S[ | S | + | - ]

	This command controls the screen swapping.  There are three
	options:

	- The default is to display the current status of the screen
	  swapping: on, off, or smart.

	- S Sets smart swapping.

	- + Will turn screen swapping on.

	- - Will turn screen swapping off.

      SeeAlso: Alt-S;Toggle Swapping.


    Trace
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    T [count]

	Single steps one instruction in the target.

      SeeAlso: F8;Trace.


    Unassemble
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    U [address]

	This command will disassemble the program memory at the
	specified address and display it as processor instructions.  MMD
	can disassemble all 8086 instructions, most real mode 286
	instructions and all non-32 bit 387 co-processor instructions

	When in window mode all the output will be in the Unassemble
	window.

	The default segment for the address is the current code segment.


    View Output Screen
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    V, \

	In screen swapping modes this command will switch to the output
	screen.  MMD will then wait for a key to be pressed before
	returning to the debugger display.

      SeeAlso: F4;View Output Screen.


    List Watch
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    W

	The List Watch command will display all the current watches,
	their results and any comments that are defined for them.


    Write File
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    W "filename" range

	Writes the memory in the range to the specified file.


    Watch Memory
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    W[format] range [; comment]

	This will add an area of memory to the watch list.  The same
	comments apply to the format and range as in the Dump Memory
	command.  The default dump size is one byte and the default
	format is a hexadecimal word.

	The comment is an optional section of text that can be used as a
	simple description of the memory region being watched to serve
	as a reminder to you.

      SeeAlso: Y;DeleteWatch


    Watch an Expression
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    W? expression[,format] [; comment]

	This command will add an expression to the Watch list.	The
	style of this expression is identical to that of the Evaluate
	Expression command.

	If the expression cannot be evaluated by MMD then it will not be
	added to the watches.

	The comment is an optional line of text that can be used as a
	simple description of the expression being watched to serve as a
	reminder.

      SeeAlso: Y;Delete Watch


    Write Listing
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    WL "filename" range

	Writes the unassembly listing of the memory in the range to a
	text file.  This will be a text file with the same formatting as
	the current unassembly options.

      SeeAlso: OB;Byte Decoding OC; Unassembly case.


    Set WatchPoint (Global Breakpoint)
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    WP? expression[,format] [; comment]

	Sets a watchpoint, when the program is running it is put into
	single step mode and the expression is evaluated on each
	instruction executed.  When it becomes true the program will be
	interrupted.  Another use of the watchpoint command is to slow
	execution of the target.

      SeeAlso: Y;Delete Watch


    Delete Watch
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
    Y list

	Deletes any watches from the current watches


    9 Configuration
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

    9.1 MMDCFG

	MMDCFG can be used to configuration MMD.

	Each project (if they are in separate directories) can have
	different default configurations as appropriate.

	During initialising MMD will search for a configuration file
	called 'MMD.CFG', a different configuration file can be given
	with the /C command line option.  When initialising MMD
	determines its configuration in the following order of priority:

	Options given on the MMD command line will override any default
	of configuration file settings.

	- A specific configuration file given with the /C command line
	  option.

	- A CFG file in the current directory.

	- A CFG file in the same directory as MMD.EXE.

	- If no configuration file is found then MMD will use the
	  options saved inside its EXE file.

	MMDCFG menus:

      þ Debugging

      Keyboard Keeper: None, DOS, PIC

      SeeAlso: /KP, /KD.


      PIC Keeper IRQ Base

	This option displays the current interrupt vectors for the
	chosen new IRQ base.  All entries in the selected range must be
	marked Unused, MMD will allow you to select any range but if the
	interrupts are being used by other software then conflicts will
	occur.

      SeeAlso: /KP.


      Switch DOS PID: On, Off.

      SeeAlso: /I


      Expression Language: Assembler, A86, C, Pascal

      SeeAlso: /L


      Default Radix: 2, 8, 10, 16

      SeeAlso: N;Set Radix


      Default Expression Format: Hex, Unsigned, Decimal

	Sets the default output format for the ?; Evaluate expression
	command.


      þ Screen

      Screen Height: Default, 25, 28, 43 ,50

      SeeAlso: /H, H;Set Screen Height.


      Restrict Height changes: On,Off

      SeeAlso: /VN


      Default Output Mode: Window, Screen, DOS

      SeeAlso: /S, /D


      Default Swapping Mode: Smart, On, Off

      SeeAlso: S;Set Swapping Mode


      Default Swapping Type: Standard, Register, VGABIOS, Dual

      SeeAlso: /VS, /VR, /VR, /VB, /Do, /2


      VGA Palette Saving: On,Off

      SeeAlso: /VP


      EGA/VGA Complete Save: On,Off

      SeeAlso: /VG


      Byte Decoding: On, Off

      SeeAlso: OB;Set Option: Byte Decoding.


      Unassembly Case: Upper, Lower

      SeeAlso: OU;Set Option: Unassembly Case.


      Horizontal Register Window: Open, Close

      SeeAlso: Ctrl+F2;Toggle Horizontal Register Window.


      Vertical Register Window: Open, Close

      SeeAlso: F2;Toggle Vertical Register Window.


      Online Help: Include, Exclude

      SeeAlso: /H


      þ Keys

      Key Definitions: Microsoft, Borland, Custom

	The keys menu allows you to set the default MMD key definitions
	to the Microsoft, Borland or a Custom setup.

      SeeAlso: /KM, /KB.

      Break key

	Sets the MMD keyboard break combination.  By default this will
	be Ctrl-Break (Note that MMD distinguishes between Ctrl-Break
	and Ctrl-C, this allows Ctrl-C to be used when a DOS break is
	specifically required).  Any key combination can be used as the
	MMD keyboard break, if the key has a non standard scan code
	(such as enhanced keyboards which have extra keys such as Macro)
	then MMDCFG will display the hexadecimal scan code it received.

	Customise Keys

	Selecting the Customise keys displays a screen with a list of
	all MMD functions.  To change a key definition select the
	function you wish to assign a new key to and then press the
	desired key.  If the key does not change then it has already
	assigned or is key that has a fixed definition.  Customise Key
	will initially display the current key selection for
	modification which is Microsoft, to base the modifications on
	Borland key definitions select Borland keys before enterring
	Customise Keys.

      þ Colours

	Allows the MMD screen colours to be set.

      þ Directory

	This is only required if MMD is running under DOS version 2.0 or
	below, with later versions of DOS MMD is able to determine the
	directory it was loaded from and search for a CFG file there.
	Alternatively this option can be used to specify any directory
	that MMD should search for a CFG file.

      þ Save

	Saves the changes to a CFG file or into MMD.EXE.  Note that if
	the options are written to the MMD executable they cannot be
	reloaded, so if they require further editing they should also be
	saved to a separate CFG file.


    10 Default Key Definitions
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

    10.1 Default Microsoft Keys

	Key		    Definition
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	Command Line Editing.
	Escape	       Clear command line
	Left
	Right
	F3	       Replay Command

	Screen Keys.
	F4	       View Output Screen
	Alt+S	       Toggle Screen Swapping

	Window Keys.
	Up	       Cursor up
	Down	       Cursor down
	PgUp	       Scroll up one screen.
	PgDn	       Scroll down one screen.
	Shift+Up       Move secondary window up one line
	Shift+Down     Move secondary window down one line
	Shift+PgUp     Scroll secondary window up one screen
	Shift+PgDn     Scroll secondary window down one screen
	Ctrl+Home      Cursor to Top
	Ctrl+End       Cursor to Bottom

	Window Control.
	F2	       Toggle Vertical Register Window
	F6	       Change Window
	Ctrl+F2        Toggle Horizontal Register Window
	Ctrl+G	       Expand Command Window
	Ctrl+T	       Shrink Command Window

	Assembler Window.
	Ctrl+Right     Byte Adjust Up
	Ctrl+Left      Byte Adjust Down
	Ctrl+N	       New CS:IP
	Ctrl+O	       Origin
	Ctrl+P	       NOP Instruction

	Debugging.
	F5	       Go
	F7	       Go To Cursor
	F8	       Trace
	F9	       Toggle Breakpoint
	F10	       Proceed

	Help.
	F1	       Help
	Tab	       Next Topic Link
	Alt+B	       Sequential Next Topic
	Alt+F	       Sequential Previous Topic
	Alt+F1	       Previous Topic
	Ctrl+F1        Next Topic
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ


    10.2 Default Borland Keys

	Key		    Definition
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	Command Line Editing.
	Escape	       Clear command line
	Left
	Right
	F3	       Replay Command

	Screen Keys.
	Alt+S	       Toggle Screen Swapping
	Alt+F5	       View Output Screen

	Window Keys.
	Up	       Cursor up
	Down	       Cursor down
	PgUp	       Scroll up one screen.
	PgDn	       Scroll down one screen.
	Shift+Up       Move secondary window up one line
	Shift+Down     Move secondary window down one line
	Shift+PgUp     Scroll secondary window up one screen
	Shift+PgDn     Scroll secondary window down one screen
	Ctrl+Home      Cursor to Top
	Ctrl+End       Cursor to Bottom

	Window Control.
	F6	       Change Window
	Ctrl+F2        Toggle Horizontal Register Window.
	Alt+F2	       Toggle Vertical Register Window.
	Ctrl+G	       Expand Command Window
	Ctrl+T	       Shrink Command Window

	Assembler Window.
	Ctrl+Right     Byte Adjust Up
	Ctrl+Left      Byte Adjust Down
	Ctrl+O	       Origin
	Ctrl+N	       New CS:IP
	Ctrl+P	       NOP Instruction

	Debugging.
	F2	       Toggle Breakpoint
	F4	       Go To Cursor
	F7	       Trace
	F8	       Proceed
	F9	       Run

	Help.
	F1	       Help
	Tab	       Next Topic Link
	Ctrl+F1        Next Topic
	Alt+F1	       Previous Topic
	Alt+B	       Sequential Next Topic
	Alt+F	       Sequential Previous Topic
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ


    11 Operator Precedence Reference
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	These tables summarise the various operators supported by
	MegaDebugger.  These operators are listed in decreasing
	precedence, and operators that are grouped together have the
	same precedence.  All the languages support the use of
	parentheses.  None of the memory reference operators are
	supported by MMD (assembler [] or C * ).

    11.1 Assembler Language Operators

	Operator	   Description
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	-		   Unary Minus
	+		   Unary Plus
	NOT		   Bitwise NOT
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	*		   Multiplication
	/		   Division
	MOD		   Modulus
	SHL		   Left shift
	SHR		   Right shift
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	+		   Addition
	-		   Subtraction
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	EQ		   Equality
	NE		   Inequality
	LT		   Less than
	LE		   Less than or equal to
	GT		   Greater than
	GE		   Greater than or equal to
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	AND		   Bitwise AND
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	XOR		   Bitwise XOR
	OR		   Bitwise OR
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	The NOT operator in both MASM and TASM is defined to have the
	same precedence as the AND operator.  However the debugging
	assumes that all unary operators have a higher precedence than
	binary operators.

	All logical Assembler operators return 0FFFFh for a true result
	and 0 for false.

	digitsH Hexadecimal
	digitsD Decimal digits
	digitsB Binary digits
	digitsO Octal digits
	digitsQ Octal


    11.2 C Language Operators

	Operator	   Description
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	-		   Unary Minus
	!		   Logical Negation
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	*		   Multiplication
	/		   Division
	%		   Modulus
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	+		   Addition
	-		   Subtraction
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	<<		   Left shift
	>>		   Right shift
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	<		   Less than
	<=		   Less than or equal to
	>		   Greater than
	>=		   Greater than or equal to
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	==		   Equality
	!=		   Inequality
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	&		   Bitwise AND
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	^		   Bitwise XOR
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	|		   Bitwise OR
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	&&		   Logical AND
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	||		   Logical OR
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	No assignment operators are supported by MMD including the C
	auto assignment operators (++ and --).

	0Xdigits  Hexadecimal
	0Ndigits  Decimal
	0digits   Octal


    11.3 Pascal Language Operators

	Operator	   Description
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	-		   Unary Minus
	+		   Unary plus
	NOT		   Bitwise NOT
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	*		   Multiplication
	/		   Division
	DIV		   Division
	MOD		   Modulus
	AND		   Bitwise AND
	SHL		   Left shift
	SHR		   Right shift
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	+		   Addition
	-		   Subtraction
	OR		   Bitwise OR
	XOR		   Bitwise XOR
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	<		   Less than
	<=		   Less than or equal to
	>		   Greater than
	>=		   Greater than or equal to
	=		   Equality
	<>		   Inequality
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	MMD supports only the INTEGER forms for each operator, therefore
	there are no equivalents for the BOOLEAN logical and and or
	operators.

	Although the type of the / division operators result is defined
	as REAL in Pascal, MegaDebugger does not support this data type
	and so the result will be integer.

	$digits   Hexadecimal
	#digits   Decimal


    11.4 A86 Language Operators

	Operator	   Description
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	-		   Unary Minus
	+		   Unary Plus
	NOT		   Bitwise NOT
	!		   Logical NOT
	BIT		   Bit Number
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	*		   Multiplication
	/		   Division
	MOD		   Modulus
	SHL		   Left shift
	SHR		   Right shift
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	+		   Addition
	-		   Subtraction
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	EQ		   Equality
	NE		   Inequality
	LT		   Less than
	LE		   Less than or equal to
	GT		   Greater than
	GE		   Greater than or equal to
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	AND		   Bitwise AND
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
	XOR		   Bitwise XOR
	OR		   Bitwise OR
	ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	The NOT operator in A86 is defined to have the same precedence
	as the AND operator.  However MMD assumes that all unary
	operators have a higher precedence than binary operators.

	All logical Assembler operators return 0FFFFh for a true result
	and 0 for false.

	0digits   Hexadecimal
	digitsH   Hexadecimal
	digitsD   Decimal
	digitsB   Binary
	digitsO   Octal
	digitsQ   Octal
	digitsXH  Hexadecimal
	digitsXD  Decimal
	digitsXB  Binary
	digitsXO  Octal
	digitsXQ  Octal

	The underscore '_' character can be used to separate digits.


    12 Error Messages
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

    12.1 Initialisation Errors

	All error messages MMD displays on the output screen are
	prefixed with the '<MMD>' string to distinguish them from any
	possible target output.

      þ Cannot find target file : "xxx"

	This means that MMD cannot find the target file you specified on
	the command line.  Check that path and file name and try again.

      þ Conflicting command line switches.

	When processing the command line options you supplied
	MegaDebugger found two switches that conflicted.  For example
	specifying Screen mode and DOS mode together (/S /D) or two
	language specifiers.

      þ Failure loading target file in DOS LOADEXEC.

	DOS could not run the target program.  The most common cause of
	this is that the program is too large to fit into the remaining
	free memory.  Other causes are that the file is not a valid EXE
	or COM file, the memory allocation chain is corrupted or MMD has
	insufficient access rights to execute the file.

      þ Internal memory allocation failure.

	This error message should never appear, as MMD makes only one
	call to the DOS memory block.  If this message does appear it is
	likely that your system memory has been corrupted (not unusual
	when debugging an errant program), reboot and try again.

      þ Invalid PIC base interrupt : "xx"

	The valid range for the new PIC base interrupts are from D8-F0h.

      þ Missing or invalid configuration file : "xxx"

	The configuration file specified with the /C command line option
	could not be found or was not a valid MMD configuration file.

      þ PIC has already been reprogrammed by another VCPI client.

	When EMM386 or a similar memory manager is running MMD is
	required to notify the protected mode manager when it reprograms
	the PIC controller to the new interrupt base.  However if
	another program has already changed the settings then MMD is not
	allowed to make any further changes.

      þ Target is not an executable file : "xxx"

	The target file specified in the command line is not a file.

      þ Unknown language type specified.

	Only four languages are supported by MMD /LA; Assembler, /LC; C,
	/LP; Pascal and /L8; A86.

      þ Unknown screen height specified : "xx"

	MMD supports only 25 and 43 line modes on EGA cards and 25,28,43
	and 50 with VGA.  MDA and CGA support only 25 line modes.

      þ Unknown switch : "xx"

	Use MMD /? for a list of valid command line switches.

      þ VCPI did not allow PIC to be reprogrammed.

	For some reason the call to notify the VCPI protected mode
	manager of the changes to the hardware interrupts failed.


    12.2 Command Errors

      þ Bad Expression

	The expression that you have entered cannot be evaluated by MMD.
	This is usually caused when an operator is misplaced or a
	register name is misspelt in the expression.

      þ Bad Flag

	There are two possible causes for this error:

	- The flag string you supplied to the Register command contained
	  a value that was not the name of a flag.

	- The string contained conflicting values for the same flag.

      þ Bad Format Character

	The character supplied after an expression or in the Dump
	command is not one of the format characters MegaDebugger
	recognises.

      þ Bad Register

	The register name given as a parameter to the Register command
	was not a valid 16-bit register name.

      þ Breakpoint Error

	This error occurs when using the Set Breakpoint command, and you
	try to set a new breakpoint at the same address as another
	breakpoint

      þ Closing Quote Character is Missing

	When evaluating either a quoted character constant in an
	expression, or in a set of values MMD reached the end of input
	string before it found a closing quote character.

      þ Divide by Zero

	The value derived for the right hand side of a division or
	modulus operator was equal to zero.  The result of a division by
	zero is mathematically undefined.

      þ Extra Characters on Line

	MMD has fulfilled the parameters for a particular command but
	there are still excess characters remaining on the line.

      þ File Error

	This error occurs when MMD cannot open, write to, or close the
	file given for the W;Write File or WL;Write Listing commands.

      þ MCBs Corrupted

	This occurs when the Memory Information command detects an error
	in the structure of the DOS memory allocation system.  This is a
	serious error and it is unlikely that you will be able to exit
	without the system crashing.

      þ No Free Watches

	MegaDebugger limits the number of watches you can define to 10,
	this error is caused if you attempt to add another watch after
	this limit has been reached.

      þ Syntax Error

	A syntax error occurs when MMD cannot convert the parameters of
	a command into the required format.  There are four conditions
	that will cause this error:

	- The start address in a range is larger than the final address.

	- One of the items in the list cannot be converted, lists can
	  contain only values between 0 and 9.

	- One of the items in a set of values cannot be converted, or
	  the value exceeds one maximum number that can be stored in one
	  byte; 255.

	- An incorrect number of parameters was supplied, usually when a
	  complete range is not given.

      þ Unbalanced Parenthesis

	While evaluating an expression the end of the string was reached
	and there were unclosed parenthesis.  There must be a matching
	closing parenthesis ')' for each opening parenthesis '(' and
	vice versa.

      þ Unknown Command

	The first non space character on the command line did not match
	any of MMD's command names.


    13 Known Bugs
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	/KP does have occasional problems with memory manages such as
	EMM386 and QEMM.

	Dual monitor support has not been used with two actual monitors,
	but has been thoroughly tested as far as possible on a single
	monitor.

	MMD does not install its own critical error handler so when
	writing files from MMD the target's handler will be invoked if a
	DOS error occurs.

	Swapping does not support Hercules graphics mode and cannot
	properly handle text modes which use custom (non-BIOS) fonts.

	Not all 286 instructions are support by the A; Assemble command,
	namely the extended shift instructions, 3 operand MUL and all
	protected mode instructions.  Maths coprocessor instructions are
	also not supported.

	MegaDebugger does not restore the entire hardware state.  If the
	target program is using any critical system interrupts when the
	Reload Target Program or Quit commands are used then these
	interrupts will be left containing addresses that point to
	unused memory locations that will be overwritten when next file
	is loaded.  In order to avoid crashing the computer when using
	this command always ensure that either:

	- The target program has terminated or has not begun execution.
	  When the target program exits it should always return the
	  system to a safe state.

	- If the target program is still executing then ensure that it
	  is not using any of the critical interrupts.	This can be done
	  using the Memory Information command, if any block that is
	  owned by the target program is using any of the interrupts
	  between 00f and 2Fh then it is unsafe to use the Reload Target
	  Program or Quit commands.


       When comparing MMD to commercial debuggers (TurboDebugger 3.00
       and CodeView 2.00) it was interesting to see how poorly they
       handle fundamental debugging operations:

	- MMD can handle breakpoints at normalised addresses (same
	  physical address, but different segment:offset address). Both
	  CodeView and TurboDebugger will crash if a breakpoint is
	  executed when set a normalised address, MMD does all its
	  internal address comparisons with 32 bit physical address
	  values.

	- MMD handles graphics modes much better then TD and CV,
	  especially ModeX.  TurboDebugger has a stupid 'smart' screen
	  swapping which will swap unnecessarily.  CodeView does not
	  have smart swapping.

	- MMD handles the interaction between WatchPoints and all forms
	  of breakpoint consistently.  For example: CodeView will not
	  update breakpoints with pass counts when watchpoints are set;
	  TurboDebugger will not acknowledge a true watchpoint if a
	  breakpoint exists on the line which makes the watchpoint true.


    14 Registering
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	I really want MMD to be the most useful debugger tool available
	and so would very much like to hear all comments, suggestions,
	criticisms you have.

	You can contact me at the following addresses:

	Internet:

	n1360906@student.fit.qut.edu.au [until December 1994]

	No Net Address:

	Mark Thomas
	8 Herronbee Street
	Toowoomba, Queensland
	Australia  4350.


	Other software by the same author:

      2OBJ110

	2Obj v1.10: Converts binary files directly to OBJ files.  Can
	decode GIF, PCX, LBM and CEL files and their palettes.	Freeware.

      DIV0

	Divide by Zero: the first demo by Sivris.

      DNC100

	DOOM Network Copier: Copies DOOM files from a single computer to
	up to four other machines simultaneously.

      MCD100

	MegaChangeDirectory: Replacement for Norton's CD.  Can create
	NCD compatible TreeInfo files.	Configurable.  Extended directory
	matching.  To Be Released Soon.


    15 Future Enhancements
    ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

	While this version of MMD is complete there is still a great
	deal I wish to add, which will require almost a complete rewrite
	of all the current code.  This list is in approximate order of
	priority:

	- 386 support.	The first priority is simply adding 386
	  instruction and register support.  Of course adding 386
	  debugging register and v86 mode support is very important.
	  (I have only recently upgraded from a 286)

	- Commands: I have a long list of commands to be included in the
	  next version.  The main areas are searching (forward and
	  backward global searches, case-insensitive string searches,
	  instruction searches) and debugging commands (Breakpoint on
	  entry or exit into interrupts, Go to RET, Trace into
	  Interrupt).

	- Improved memory management.  Most important is allowing MMD to
	  use high memory to free more memory under 640k but also to use
	  XMS and EMS.

	- Remote debugging.  I have already written the communications
	  drivers for serial, parallel, NETBIOS and IPX links but all
	  the MMD commands will have to be re-written to work with the
	  remote link interface.

	- Better interface: pull down menus, mouse support, resizing etc
	  (and stack and memory and output screen windows).  I
	  personally prefer to have a command line interface for
	  debugging so it will still be available.

	- Symbolic Debugging.  The original idea of MMD was to provide a
	  alternative to the large symbolic debuggers but now it seems a
	  waste not to include it.  MMD will still be primarily a
	  low-level debugger.


	I am looking for information on the following:

	- The EXE debug information format used by CodeView and
	  TurboDebugger (and Watcom, Symantec etc) and details of any
	  debugging hooks placed in executables.

	- Detecting and using 8 bit interrupt driven parallel I/O.

	- Interfacing with the NMI, particularly about building a cheap
          and safe NMI breakout switch that plugs into the bus.

	- System Management Mode.  One of the most interesting ideas I
	  have seen is to use the SMM of 386SL and 486SL for a debugger.
	  SL chips are used mainly in laptops but apparently all new
	  i486 CPUs have this mode.

[END]
