CU Amiga Super CD-ROM 17/CU Amiga Magazine's Super CD-ROM 17 (1997)(EMAP Images)(GB)[!][issue 1997-12].iso/CUCD/Programming/DiceSource/doc/dice_debugger.doc

Text File | 1994-02-13 | 33KB | 722 lines

Dice/DD                              Dice/DD

 Dice Debugger (DD) User's Manual

 OVERVIEW

 DD is a debugger designed exclusively for the DICE compiler environment.
 In previous versions of DICE, all debugging had to be done with assembly
 language debuggers or by inserting printf() calls in the code.    This is
 no longer the case!   DD takes advantage of many old and many new features
 in the DICE compiler to provide you with the ability to debug on the source
 level.    DD is both command-line and mouse driven.

 DD allows you to examine your program in a variety of display modes and
 using as many windows as you desire.  DD also features ARexx support, the
 ability to replace any of the builtin commands with an Arexx program,
 and user-definable menus with amiga-key equivalents for the commands of
 your choice.  Its point-and-click input capabilities allow you to build
 complex command lines by almost exclusively using the mouse.

 DD is designed to be OS friendly under OS versions 1.3 and 2.0 (and up).
 You may DD as many programs at a time as you like, limited only by the
 memory in your machine.  In fact, DD is so OS friendly, it is one of the
 only debuggers that can actually be used to debug itself!  To further
 enhance the usefulness of DD, full source code (written in DICE 'C'
 and A68K assembler) will be made available - you can add new commands
 and features that you need to solve your particular debugging problems.

 DICE FEATURES

 The DICE features that DD specifically takes advantage of are important
 to consider when writing your programs.  The more you take advantage of
 these great features in DICE, the better DD is able to do its job, too.

 First and foremost, the DICE compiler now supports level 1 DEBUG hunks,
 as does the SAS compiler and many available assemblers.  In order to
 enable source-level debugging capabilities of DD, you need to compile
 with the -d1 option to generate these hunks.  You can then use DICE
 or any other debugger that supports the -d1 hunk format to do source
 level debugging.

 The DICE compiler also generates the standard Amiga SYMBOL hunks.  These
 are used by DD to provide you with symbolic debugging capability.  When
 these symbols are found in the executable by DD, you will be able to
 use your symbolic names to reference subroutines, variables, and so on.
 To cause DICE to generate the symbol hunks, you must use the -s option
 when compiling.

 Lastly, DD will cause the program being debugged to call exit() under
 various circumstances.    If you decide to quit DD while partway debugging
 through a program, your program will immediately exit().  You should take
 advantage of this to have your program clean up any resources it used
 during the debugging session (close your windows, free memory allocated,
 etc.).

 DICE supports the ANSI atexit() function, which allows you to specify
 a subroutine to be executed at exit() time.  You should use the atexit()
 function to specify your cleanup routine.  ADDitionally, DICE supports
 the __autoexit keyword, which allows you to declare subroutines that
 are to be executed at exit() time as well.  Use either method, or a
 combination of both, and DD will help you to minimize the number
 of reboots you will have to do when debugging those difficult bugs.


 THEORY OF OPERATION

 A brief discussion of how DD is implemented will help you to understand
 the capabilities of the debugger more fully.

 DD has its own custom LoadSeg() routine that is used to load the executable
 from disk.  The entire executable is loaded into contiguous memory, and memory
 is allocated for your program's hunks as suggested by the CBM documentation.
 When your program is RESET (see the reset command below), your program's
 hunks are initialized from the originally loaded and relocations then performed.
 This allows you to reset your debugging session and start over without quitting
 and reloading all over again.  The symbolic and debugging information found
 in the original file are kept track of in the original file memory, to conserve
 memory.

 DD actually shares its process with the program being debugged.  This is done
 in a similar fashion to the Exec Signal Exceptions.  The main difference is that
 DD uses two stacks, one for the program being debugged and one for the debugger
 itself.  This is to eliminate the need for your program to have enough extra
 stack to support the debugger, too.  Only a single signal bit (shared among the
 display windows) and the TC_TrapCode pointer of your Task structure will be
 seen by your program while it is being debugged.  Otherwise, DD is completely
 invisible to the program and it will behave as if it were run from the CLI alone.

 While debugging, your process will be in one of two states - debugger state or
 program state.    When in debugger state, the debugger has full control, responds
 to your inputs, etc.  When in program state, your program is in full control and
 will run until it exits or until you hit a breakpoint or other stoppage (guru)
 of your program.  The debugger is careful NOT to do DOS calls which might cause
 DOS to be entered twice - DOS is not reentrant...


 GETTING STARTED

 The DD executable should be in your DCC:bin directory along with your other
 DICE executables.  DCC:bin should also be on your path.  Note that DD is
 not a PURE program so you can not make it resident!  Now you can go to
 any directory you have a DICE compiled program and debug it.  Remember to
 compile with -s -d1 to get full debugging capability.

 To launch the debugger, just type:
     1> DD myprog parm parm parm ...
 Where myprog is the name of your program (to be debugged) and parm parm parm
 is the typical CLI arguments that you would give to your program.  DD will
 open a console window for you to enter commands.

 If you are debugging a 'C' program (DD works for assembly programs, too), DD
 will automaticall set a breakpoint at _main() or @main(), which is the main()
 routine of your program.  You can quit your debugging session at any time by
 hitting ^C while the debugger is active, and DD will exit after causing your
 program to exit(20).


 DD'S WINDOWS

 You initially start DD and have a single console window to control the debugger
 from.  The top few lines of the window are used to display the CPU registers of the
 current state of your program.    All the standard 68000 Data and ADDress Registers
 are displayed, as well as the PC, and SR registers.  The individual bits of the
 condition codes (CCR) are displayed to the right of the SR.  Also, the program's
 state is displayed.  Many states are possible, but typically your program will be
 stepped, steppedover, at a breakpoint, exited, or crashed (CPU exception).  As
 you maneuver through your program with the debugger, values that change in these
 lines will be highlighted - a visual clue to what's changing.

 If you use the watchpoint features of DD, your watchpoint display will appear
 below the register display.  Below this is a general purpose scrollable display window which
 DD uses to display various information that you ask it to.  To change the information
 in the display area, you change the Display Mode to that of your choice.  Initially,
 the display area is in MIXED MODE, where your program is shown to you as lines of
 source code with disassembly intermixed.  When you start DD, your MIXED MODE
 display will show you where the PC register points.  The lines of source and
 disassembly that represent the current PC location will be highlighted - most likely
 _main or @main.

 Below the general purpose display is the Status: line, where DD will display
 its various status and error messages.    Initially, this line says:
 Status: Ready for command.

 Below the status line is the command line itself.  As you type in your commands,
 they will be displayed on the command line.  The left side of the command line
 is your prompt, which consists of some funny looking sequence of characters
 (described in the mouse input section) and the name of the source file that
 the PC is in.  It is always good to know what file your bug is in...

 And finally, below the command line are two lines reserved for display of the
 current function key bindings.    By default, these are bound to some very common
 commands that you would otherwise have to type.

 DD supports multiple windows - but all share the same command line.  You use
 the "open" command to open a new console window.  You may enter commands into
 any window.  Commands that change a window's mode or display position will affect
 the window you type into.


 MOUSE INTERFACE

 The right mouse button is used, as normal, to operate the Intuition Menus that
 are bound to the window.  The left mouse button is a select button and operates
 differently, depending on where you click.  Clicking on text in the window
 generally causes the word you clicked on to be entered onto the command line
 automatically for you.    That funny character string on the left of the prompt
 is there so you can click to generate those characters.  Clicking to the
 right of the command line is like hitting return to execute the command.
 You can click in any combination of windows to build your command lines.


 COMMAND SUMMARY

 Below is the command summary as found in the help command (help mode display).

 NAME
 again            - repeat last command
 alias            - replace command with arexx script
 bp {expr}        - set breakpoint at expression
 bp ALL           - set all breakpoints in table
 breakpoints      - display breakpoint table
 bytes {expr}     - display bytes {at expression}
 changewindow     - move/size current window
 clear expr       - clear breakpoint at expression
 clear ALL        - clear all breakpoints in table
 close            - close a display
 devs             - display Exec Device List
 dism {expr}      - change to dism mode {at expression}
 dosbase          - intelligent display of DOSBase struct
 down             - move display down one line
 eval {expr}      - evaluate an expression
 execbase         - display ExecBase (SysBase)
 fkey             - set function key definition
 go {expr...}     - set {expr...} temp breakpoints & go
 help             - online help
 hunks            - change to hunks mode
 info             - display ThisTask info
 intrs            - display Exec Intrs List
 jump {name}      - jump to public screen
 libs             - display Exec Libs List
 longs {expr}     - display longs {at expression}
 mbar             - add menu bar
 mend             - add menu end mark
 memlist          - display Exec Mem List
 mitem            - add menu item
 mixed {expr}     - change to mixed mode {at expression}
 menus            - activate a new set of user menus
 msub             - add a sub menu item
 mtitle           - add menu title
 offsets          - toggle display address/offsets
 open {type}      - open a new display
 over {range}     - stepover one instruction or range
 pagedown         - move display down one page
 pageup           - move display up one page
 rendlist         - end the arexx list
 rgetbyte {expr}  - get bytes at {expr}
 rgetcom          - get command line input
 rgetdism {expr}  - get the dissembled line
 rgeteval {expr}  - evaluate the expression
 rgetinfo {expr}  - get the program nam
 rgetline {expr}  - return the source/mixed line
 rgetlong {expr}  - get longs at {expr}
 rgetword {expr}  - get words at {expr}
 rgetpc           - return the program counter
 rputlist         - add an item to the arexx list
 rshowlist        - show the arexx list
 rstartlist       - start the arexx list
 rx rexx-script   - execute ARexx macro
 saveprefs        - save DD prefs to disk
 set {addr} {val} - set address to val
 ports            - display Exec Ports List
 process {expr}   - display process {at expression}
 resources        - display Exec Resource List
 quit             - _exit(20) & quit DD
 refresh          - refresh the window
 registers        - toggle the register display
 reset            - _exit(20) & restart program
 rstep            - toggle library call auto stepover flag
 source {expr}    - change to source mode {at expression}
 step             - step program one instruction or range
 symbols {expr}   - display symbol {at expr}
 symlist          - display sorted symbol list
 tasks            - display Exec Task Lists
 unalias          - restore command with arexx script
 up               - move display up one line
 watchbyte {expr} - set/clear (toggle) byte watchpoints
 watchclear       - clear all watchpoints
 watchlong {expr} - set/clear (toggle) long watchpoints
 watchword {expr} - set/clear (toggle) word watchpoints
 words {expr}     - display words {at expression}

 EXPRESSIONS

 The expression evaluator can handle most C style expressions, and can be used
 on the command line to set breakpoints, display source, and so on.


 KEYBINDINGS

 The following keys are bound, as defaults, in DD:

 upcursor = up
 downcursor = down
 shift upcursor = pageup
 shift downcursor = pagedown
 leftcursor = left
 rightcursor = right
 return = execute command
 HELP = toggle to help display (help = help mode, help again = previous mode)


 AREXX SUPPORT

 DD is the base name of DD's ARexx port.  The ARexx commands that are
 supported by DD are identical to those that you type in at the command
 line.  DD also has the rexx command to allow you to run rexx scripts
 as macros from inside DD.  These rexx script files should have the
 .DD extension, so you can identify which scripts are for DD.

 The ALIAS command allows you to replace any of the built in commands
 with an Arexx script of the same name (with an appended .dbug).  DD looks
 first in the current directory, then in dcc:rexx/ for the command.
 UNALIAS cancels a previous alias.  From within the ARexx script, the internal
 command can be called by name.  (as can all internal commands)

 The results of an internal command called by an ARexx program are placed
 in the ARexx result variable.

 NOTE: Aliases are part of the DD preferences saved to disk, and automatically
 loaded on starting DD.

 The Rexx port name of the first port is DD.01  Subsequent ports are named
 DD.02, DD.03, and so on.



 COMMAND DESCRIPTIONS

 AGAIN
     This command repeats the last command entered.  It is
 occasionally useful when a complicated command was entered.

 ALIAS
     This command provides a limited alias function for all internal
 commands.  When an internal command is aliased, DD looks for an AREXX
 program with the same name (with the .DD extension) and executes that
 instead of the internal command.  The internal command is still
 available, however, by specifying the name within the ARexx program.
 This allows you to, for instance, write a replacement pagedown command that
 first sends a message to the AME editor, then calls the built in DD pagedown
 command.  To save the change, the saveprefs command must be used.

 BP {expression}
 The BP command sets a breakpoint.  If the optional
 {expression} is given, DD will set the breakpoint at that address.
 The expression can also be a source line number (indicated by the
 trailing period.) DD will look up the source line specified, and set
 the breakpoint at the start of the code for that source line.  If no
 expression is given, DD sets the breakpoint at address in the Program
 Counter.  A line containing a breakpoint is underlined on the display.
 The mouse can also be used to set (and unset) breakpoints.  Just
 doubleclick on the left (address) column of the display area, and the
 breakpoint is set.  (If you doubleclick on an already set breakpoint,
 it will be unset).  If there is no more room in the breakpoint table,
 and there are unarmed breakpoints, one will be replaced by a newly
 set breakpoint;  otherwise the attempt to set a new breakpoint will
 fail.

 BP ALL
     When a breakpoint is hit, it is automatically unset.  However,
 it is still in the breakpoint table, and can be rearmed.  The bp all
 commnd rearms all breakpoints in the table.

 BREAKPOINTS
     This command displays the table containing the current
 breakpoint list, and current status.  Breakpoints can be set and unset
 directly on the table display itself.

 BYTES {expression}
     The bytes command changes the display mode of the current
 window to the bytes display.  The optional expression allows you to
 specify the start of the byte display.  (DD attempts to keep enforcer
 happy; most illegal accesses are trapped).  If no expression is
 specified, the address of the display remains the same; just the mode
 is changed.

 CHANGEWINDOW
     This command is used to move and size the curren DD window.  It
 only operates under AmigaaOS 2.0 or greater (so, why haven't you
 upgraded yet ?).  The command takes the two coordinates of the upper
 left corner of the window, the width, and the height, and moves the
 window there if possible.

 CLEAR {expression}
     This command clears the breakpoint at the expression.  If no
 expression is given, the breakpoint is cleared at the PC location.
 The breakpoint is not removed from the breakpoint table, and may be
 re-armed by the BP command.

 CLEAR ALL
     Clear all clears the entire breakpoint table.

 CLOSE
     This command closes the current display window.  If the current
 window is the only DD window open, DD exits.

 DEVS
     This command displays the current Exec Device List

 DISM {expression}
     The dism command changes the display mode of the current window
 to the disassembly display.  The optional expression allows you to
 specify the start of the disassembly display.  (DD attempts to keep
 enforcer happy; most illegal accesses are trapped).  If no expression
 is specified, the address of the display remains the same; just the
 mode is changed.

 DOSBASE
     This command displays the pulic fields of the AmigaDOS DOSBase
 structure.

 DOWN
     This command is used to move the cursor down one line.  New
 informtion is displayed at the bottom of the display area if the
 display scrolls.  This command acts the same as pressing the cursor
 down key.

 EVAL {expression}
     This command evaluates an expression, and prints the result to
 the screen.

 EXECBASE
     This command displays the current contents of the public fields
 of ExecBase.

 FKEY num definition
     This command is used to set one of the ten function key
 definitions.  The command takes the function key number (from 1 to 10)
 and the definition string.

 GO {expression}
     The go command sets all the breakpoints in the breakpoint
 table, and starts execution on the program being debugged.  Execution
 begins at the expression if provided; otherwise execution begins at
 the address contained in the program counter (PC).  The program runs
 at full speed; the debugger does not regain control until either the
 program exits, or the program encounters one of the breakpoints.  If
 more control over the execution is desired, you should use one of the
 single step functions (step or over) instead.

 HELP {command}
     Provide short online help list

 HUNKS
     This command changes the current display to a table of the
 hunks in the progra being debugged.

 INFO
     This command displays information on the current task, taken
 from the task structure.

 INTRS
     The intrs command displays the Exec interrupt list.

 JUMP {name}
     The jump command is used to jump a DD window to another public
 Intuition screen.  With no argument, the jump command jumps the window
 to the next public screen.  If an argument is specified, the jump
 command jumps the window to that public screen.  If the screen does
 not exist (or there is only one public screen, ie Workbench) nothing
 happens.

 LIBS
     This command diplays the Exec library list.

 LONGS {expression}
     The longs command changes the display mode of the current
 window to the longs display.  The optional expression allows you to
 specify the start of the longs display.  (DD attempts to keep enforcer
 happy; most illegal accesses are trapped).  If no expression is
 specified, the address of the display remains the same; just the mode
 is changed.

 MBAR slot
     This command is used when setting up the programmable menu
 system, to add a menubar at the specified slot.  The slot can be a
 positive integer (from 0 to 127) or -1 (which tells DD to append the
 new menu bar to the existing menus) When this command is used, menus
 are automatically turned off, and must be turned on with the menus
 command.

 MEND
     This command is used when setting up the programmable menu
 system, to add a menu end marker at the specified slot. The slot can
 be a positive integer (from 0 to 127) or -1 , which tells DD to append
 the new menu end marker to the existing menus. When this command is
 used, menus are automatically turned off, and must be turned on with
 the menus command.

 MEMLIST
     This command displays the current Exec memory lists

 mitem slot label command shortcutkey
     This command is used when setting up the programmable menu
 system, to add a menu item at the specified slot. The slot can be a
 positive integer (from 0 to 127) or -1 , which tells DD to append the
 new menu item to the end of the existing menus.  The label is what is
 displayed in the menu.  The command is what is executed when the menu
 item is selected.  The optional shortcut key is used to assign a Right
 Amiga key shortcut to the function.  When this command is used, menus
 are automatically turned off, and must be turned on with the menus
 command.

 MIXED {expression}
     The mixed command changes the display mode of the current
 window to the mixed display.  The optional expression allows you to
 specify the start of the longs display.  (DD attempts to keep enforcer
 happy; most illegal accesses are trapped).  If no expression is
 specified, the address of the display remains the same; just the mode
 is changed.  The mixed mode display consists of the source for the
 program being debugged (if available) interspersed with the
 disassembled instructions that each source line compiles to.

 MENUS
     This command activates the DD menus.

 MSUB slot label command shortcutkey
     This command is used when setting up the programmable menu
 system, to add a menu subitem at the specified slot. The slot can be a
 positive integer (from 0 to 127) or -1 , which tells DD to append the
 new menu subitem to the end of the existing menus.  The label is what
 is displayed in the menu.  The command is what is executed when the
 menu item is selected.  The optional shortcut key is used to assign a
 Right Amiga key shortcut to the function.  When this command is used,
 menus are automatically turned off, and must be turned on with the
 menus command.  Sub items are automatically attached to the nearest
 previous menu item.  DD does not support sub items under 1.3.
 Instead, they are treated as menu items.

 MTITLE slot label
     This command is used when setting up the programmable menu
 system, to add a menu title at the specified slot.  The slot can be a
 positive integer (from 0 to 127) or -1 (which tells DD to append the
 new menu title to the existing menus) Each menu title must have at
 least one menu item following it.  The label is used as the menu
 title.  When this command is used, menus are automatically turned off,
 and must be turned on with the menus command.

 OFFSETS
     This command toggles the display of addresses as either offsets
 from a listed symbol name or plain hex addresses.

 OPEN {type}
     This command is used to open a new DD display.  If no type is
 specified, a new window is opened with the same display as the current
 window.  Otherwise, a display of the specified type is opened.  The
 displys are somewhat independent ... each can display a different
 address, but share breakpoints, the registers, Rexx port name, etc.

 OVER {range}
     This command is used to single step the program under debug,
 stepping over subroutines.  The subroutine is executed, and control
 returns to the debugger at the instruction immediately following.
 The optional range parameter allows you to set up an address range
 for execution.  Control returns to the debugger if the program
 under debug leaves the range.

 PAGEDOWN
     This command is used to move the cursor down one page.  New
 informtion is displayed at the bottom of the display area if the
 display scrolls.  This command acts the same as pressing the shifted cursor
 down key.

 PAGEUP
     This command is used to move the cursor up one page.  New
 informtion is displayed at the top of the display area if the
 display scrolls.  This command acts the same as pressing the shifted cursor
 up key.

 RENDLIST
     This command is used to signal completion of a buffer list creation
 by an external ARexx program.  DD allows external commands to create an
 information list through its ARexx port.  The list is then available for
 display;  DD handles scrolling, refresh of the list, and so on.  This command
 tells DD that the list is complete and ready for display.

 RGETBYTE {expression}
     This command is used to get one line of bytes at expression.  If no
 expression is provided, the bytes will be fetched from the location specified
 by the PC.  The bytes are returned in the ARexx RESULT variable.

 RGETCOM
     This command is used to get the command line.  The command line
 is returned in the ARexx RESULT variable.

 RGETDISM {expr}
     This command is used to get one line of disassembly at expression.  If no
 expression is provided, the disassembly will be fetched from the location
 specified by the PC.  The bytes are returned in the ARexx RESULT variable.

 RGETEVAL {expr}
     This command evaluates the expression, and passes it back in the
 ARexx RESULT variable.

 RGETINFO {expr}
     This command is used to get the program name and current line number
 of the expression.  If no expression is provided, the information will be
 fetched from the location specified by the PC.  The results are returned in
 the ARexx RESULT variable.

 RGETLINE {expr}
     This command is used to get one line of mixed display at expression.
 If no expression is provided, the disassembly will be fetched from the location
 specified by the PC.  The lines are returned in the ARexx RESULT variable.

 RGETLONG {expr}
     This command is used to get one line of long words at expression.  If no
 expression is provided, the long words will be fetched from the location specified
 by the PC.  The bytes are returned in the ARexx RESULT variable.

 RGETWORD {expr}
     This command is used to get one line of words at expression.  If no
 expression is provided, the words will be fetched from the location specified
 by the PC.  The bytes are returned in the ARexx RESULT variable.

 RGETPC
     This command is used to get the value if the current Program
 Counter (PC).  The bytes are returned in the ARexx RESULT variable.

 RPUTLIST
     This command is used to add a line of text to the buffer list being
 created by an external ARexx program.  DD allows external commands to create an
 information list through its ARexx port.  The list is then available for
 display;  DD handles scrolling, refresh of the list, and so on.  This command
 gives a line for DD to add to the list.

 RSHOWLIST
     This command is used to display the external buffer list previously
 created with the rputlist commands.

 RSTARTLIST
     This command is used to signal the start of creation of a buffer list
 by an external ARexx program.  DD allows external commands to create an
 information list through its ARexx port.  The list is then available for
 display;  DD handles scrolling, refresh of the list, and so on.  This command
 initializes the buffer list.

 RX rexx-script
     This command executes an external ARexx script file.  DD will treat any
 command given by the user which is not an internal command as an ARexx
 command;  the rx command is to execute scripts with the same name as
 internal commands, or the same name as a symbol from the program under debug.

 SAVEPREFS
     This command saves the configuration file for DD to dcc:config/dd.config.
 This file contains information on which commands are aliased, window position
 information, etc.

 SET {address} {value}
     This command is used to set the address to the specified value.  If the
 value is not given, a 0 will be used.  This command can also change the value
 of the registers  (A register is denoted by the trailing :, ie A0: or PC:).

 PORTS
     This command is used to display the Exec port list.

 PROCESS {expression}
     This command is used to display process information for the process
 at {expression}.  If no expression is given, the address contained in the
 Program Counter will be used instead.

 RESOURCES
     This command is used to display the Exec resources list.

 QUIT
     This command calls the exit routine (_exit or @exit) of the program
 under debug with a 20 in D0, then exits from the DD program.

 REFRESH
     Refresh the current window display.

 REGISTERS
     This command toggles the register display.  Some windows contain the
 register display by default (the mixed mode display, for instance).  Others
 do not (the source display).  The registers command changes this for a
 particular window.  Once the registers command has been executed in a
 window, the register display is on 'manual', and just obeys the register
 command.

 RESET
     This command calls the exit routine (_exit or @exit) of the program
 under debug with a 20 in D0, then restarts the it.

 RSTEP            - toggle library call auto stepover flag
     This command toggles the auto stepover flag for libraries.  If rstep
 is on, then DD will automatically use OVER when asked to STEP into an
 Amiga rom routine.

 source {expression}
     The source command changes the display mode of the current window
 to the source display.  The optional expression allows you to
 specify the start of the source display.  (DD attempts to keep
 enforcer happy; most illegal accesses are trapped).  If no expression
 is specified, the address of the display remains the same; just the
 mode is changed.

 STEP
     This command is used to single step the program under debug.
 The optional range parameter allows you to set up an address range
 for execution.  Control returns to the debugger if the program
 under debug leaves the range.

 SYMBOLS {expression}
     This command is used to display the symbol table for the program
 under debug.  Breakpoints can be set from this table.  This table is
 ordered by address.

 SYMLIST
     This command is used to display the symbol table for the program
 under debug.  This table is sorted.

 TASKS
     This command will display the Exec task list.

 UNALIAS
     This command removes a previously set alias.  To save the change,
 the saveprefs command must be used.

 UP
     This command is used to move the cursor up one line.  New
 informtion is displayed at the top of the display area if the
 display scrolls.  This command acts the same as pressing the cursor up key.

 WATCHBYTE {expression} - set/clear (toggle) byte watchpoints
     This command is used to see the values of bytes at the specified
 expression.  This command  sets or clears a watchbyte.  If there are any
 watchbytes,  the display is added to the current DD window;  otherwise there is
 no watchbyte display.  The expression can be an address, or a symbol.

 WATCHCLEAR       - clear all watchpoints
     This command removes all watchbytes, watchwords, and watchlongs.

 WATCHLONG {expr} - set/clear (toggle) long watchpoints
     This command is used to see the values of longss at the specified
 expression.  This command  sets or clears a watchlong.  If there are any
 watchlongs,  the display is added to the current DD window;  otherwise there is
 no watchlong display.  The expression can be an address, or a symbol.

 WATCHWORD {expr} - set/clear (toggle) word watchpoints
     This command is used to see the values of words at the specified
 expression.  This command  sets or clears a watchword.  If there are any
 watchwords,  the display is added to the current DD window;  otherwise there is
 no watchword display.  The expression can be an address, or a symbol.

 WORDS {expression}
     The dism command changes the display mode of the current window
 to the word display.  The optional expression allows you to
 specify the start of the word display.  (DD attempts to keep
 enforcer happy; most illegal accesses are trapped).  If no expression
 is specified, the address of the display remains the same; just the
 mode is changed.