Liren Large Software Subsidy 7/07.iso/c/c496/3.img/VID_HELP.WPK/WVIDEO.HLP

Text File | 1991-08-20 | 285.8 KB | 7,269 lines

All help topics must be stored in order of the ASCII collating sequence.
Each topic is identified by a header consisting of a string of 4 colons
followed by the topic name.  Any alphabetic characters must be entered in
upper-case.
::::BREAK
┌──────────────────────────────────────────────────────────────────────┐
│ Break                                                                │
│     /Activate    "*" | index_expr | "/" addr_expr                    │
│     /Deactivate  "*" | index_expr | "/" addr_expr                    │
│     [/Set]       addr_expr  [ cmd_list ]                             │
│     /Clear       "*" | index_expr | "/" addr_expr                    │
└──────────────────────────────────────────────────────────────────────┘

A break point defines a place in an application where we would like
execution to suspend so that we might examine the current environment.
A break point may be defined by using the /Set qualifier or removed by
using the /Clear qualifier, enabled by using the /Activate qualifier or
disabled by using the /Deactivate qualifier.  Up to 7 break points may
be defined by using the /Set qualifier.  /Set is implied when no other
qualifiers are specified.

Example:
   DBG>break/set main_
   DBG>break main_

In the above example, two equivalent commands are shown.  A break point
is defined and automatically activated for the memory location defined
by the global symbol main_.  Only one break point may be specified for a
particular location in memory.  A "set" break point is indicated in the
Source and Assembly windows by a left-pointing arrow (L).

A break point may also be specified in terms of the module name and line
number.

Example:
   DBG>break calendar@36

After the command is entered, an arrow (L), indicating a break point,
appears at the start of the line.

Line numbers are shown in the Source window.  Source line information
must be available in order to show source line numbers.

   1. Either compiler options "d1" or "d2" must have been specified when
      the module was compiled.
   2. The "debug lines" or "debug all" linker option must have preceded
      the name of the object file containing the module when the
      application was linked.

The module name need not be specified when it is the current module
under examination.

Example:
   DBG>break @36

A break point may also be set or cleared with the mouse.  To set a break
point, double-click the mouse on the desired source line or assembly
line.  A subsequent double-click on the same line will clear the break.

When the thread of execution encounters an active break point,
application execution will suspend and the debugger is entered.  If one
or more debugger commands were specified when the break point was
defined, the debugger commands are executed first.  The command list
that follows the address expression in the Break/Set command is defined
as follows:

   cmd_list ::= "{" [cmd] { ";" [cmd] } "}"

This is simply a VIDEO command line placed inside of braces.

Notes:

   1. Execution of the application may be resumed if one of the commands
      was a Go command; otherwise the debugger prompts the user for a
      new command.

      Example:
         DBG>do look_count = 0
         DBG>break/set lookup { do look_count++; go/keep }

      Each time the "lookup" routine is entered, the debugger will
      increment the user-defined variable look_count and resume
      execution (keeping any user-defined temporary break point).  When
      execution of the application terminates, the current value of
      look_count may be examined with the Print command to determine how
      many times the "lookup" routine was executed.

   2. If no arguments are specified to the Break command, the currently
      defined break points will be displayed.  The first one shown is
      break point number 1, the second one shown is break point number
      2, and so on.  These are called the break point indices.  Active
      break points are shown in "active" attributes, inactive ones are
      shown in "plain" attributes.  See the description of the Paint
      command for a discussion of attributes.

   3. When activating, deactivating or clearing a break point, either
      the break point index or the address must be specified.  If "*" is
      specified as the break point index then all break points are
      affected.

      Example:
         DBG>break/set main_; break/deactivate 1
         DBG>break/set main_; break/deactivate /main_

      In both examples, a break point is set and then a break point is
      deactivated.  In the first example, the break point set for
      "main_" is deactivated only if no other break points have been set
      (since it will then be break point number 1).  The second example
      illustrates how the break point for main_ will be deactivated
      under any circumstances.

      Example:
         DBG>break/activate 2; break/deactivate 1

      Breakpoint number 2 is activated and 1 is deactivated.

   4. The specified address need not be the name of a symbol or module
      name and line number.

      Example:
         DBG>break es:di

      A break point is set for the location specified by the contents of
      the ES:DI register pair.

      Example:
         DBG>break/deactivate /bx

      The break point whose address is specified by the contents of the
      CS:BX register pair is deactivated.

   5. The specified address can be "." which corresponds to the line of
      source code or assembly code most recently examined.

      After the command is entered, an arrow (L), indicating a break
      point, appears at the start of the line.

   6. All break points may be removed in a single command.

      Example:
         DBG>break/clear *

      The asterisk refers to all break points.
::::CALL
┌──────────────────────────────────────────────────────────────────────┐
│ Call [/Far | /Interrupt | /Near]                                     │
│         start_addr_expr [ "(" [arg_list] ")" [ "/" | print_list ] ]  │
└──────────────────────────────────────────────────────────────────────┘

The Call command may be used to call any routine present in the system.
The user specifies a starting address expression for the routine that is
to be called.  The expression must evaluate to the segment and offset of
the routine to be called.  The routine may be one of three types:

   /Far start_addr_expr ["(" [arg_list] ")" [ "/" | print_list ]]

       A "far" routine is one that eventually returns to its caller by
       using a "far return" instruction (RETF).  In 16-bit mode, a
       32-bit return address (segment and offset) is placed on the stack
       by the debugger so that the routine will return to the debugger.
       In 32-bit mode, a 64-bit return address (segment and offset) is
       placed on the stack by the debugger so that the routine will
       return to the debugger.  The "far" call and return mechanism is
       used in the big code models (medium, large, and huge).

   /Interrupt start_addr_expr ["(" [arg_list] ")" [ "/" | print_list ]]

       An "interrupt" routine is one that eventually returns to its
       caller by using an interrupt return instruction (IRET, IRETD).
       In 16-bit mode, a 32-bit return address (segment and offset) and
       the current contents of the flags register are placed on the
       stack by the debugger so that the interrupt routine will return
       to the debugger.  In 32-bit mode, a 64-bit return address
       (segment and offset) and the current contents of the flags
       register are placed on the stack by the debugger so that the
       interrupt routine will return to the debugger.  Note that an
       interrupt routine is called by its address, not an interrupt
       number.

   /Near start_addr_expr ["(" [arg_list] ")" [ "/" | print_list ]]
       A "near" routine is one that eventually returns to its caller by
       using a "near return" instruction (RET).  In 16-bit mode, a
       16-bit return address (offset) is placed on the stack by the
       debugger so that the routine will return to the debugger.  In
       32-bit mode, a 32-bit return address (offset) is placed on the
       stack by the debugger so that the routine will return to the
       debugger.  The "near" call and return mechanism is used in the
       small code models (small, compact, flat).


Call Argument List
──────────────────
An argument list may be specified for the routine to be invoked.  If one
is specified, it takes the following form:

   arg_list ::= [ arg_expr { "," arg_expr } ]

   arg_expr ::= [ "/"reg_name | "/"reg_aggregate | "//" ] expr

Example:
   DBG>call rtn0( )
   DBG>call rtn1( arg1 )
   DBG>call rtn5( arg1, arg2, arg3, arg4, arg5 )

The above examples illustrate how arguments may be specified.  By
default, arguments are passed to the routine using the standard argument
passing convention.  In 16-bit mode, the standard argument passing
convention for 16-bit quantities is:

argument 1 passed in register AX

argument 2 passed in register DX

argument 3 passed in register BX

argument 4 passed in register CX

argument N passed on the stack (N >= 5).

In 32-bit mode, the standard argument passing convention for 32-bit
quantities is:

argument 1 passed in register EAX

argument 2 passed in register EDX

argument 3 passed in register EBX

argument 4 passed in register ECX

argument N passed on the stack (N >= 5).

These defaults may be changed by using the Set Call command.
Alternatively, if you wish to specify a different argument passing
convention then the "/reg_name" (register), "/reg_aggregate" (group of
registers) or "//" (stack) modifiers may be used.

Example:
   DBG>call stdrtn(/ax p1,/dx p2,/bx p3,/cx p4,// p5)
           or
   DBG>call stdrtn(/eax p1,/edx p2,/ebx p3,/ecx p4,// p5)

The above examples, in effect, illustrate the placement of arguments in
registers and on the stack according to the standard argument passing
conventions for 16-bit and 32-bit modes.

Example:
   DBG>call longtostr( /[dx ax] long_arg )

The above 16-bit example illustrates that a 32-bit argument can be
passed in a register aggregate.  Register aggregates are described in
the chapter entitled "VIDEO Expression Handling".

Example:
   DBG>call printf( //arg1, //arg2, //arg3 )

The above example illustrates how to pass all arguments on the stack.
The arguments are pushed onto the stack in a right to left order so that
(preceding the actual call) "arg1" will be on the top of the stack,
"arg2" will be next, and so on.

The arguments can be expressions and all expressions are evaluated
before the arguments are assigned to registers or placed on the stack.

Example:
   DBG>call rtn( /ax dx+1, /bx ax-cx, /cx 123)

The expressions "dx+1", "ax-cx" and "123" are evaluated.  The results of
these expressions are then assigned to the AX, BX and CX registers
respectively.  Note that the results would have been quite different if
123 had been assigned to the CX register before the expression "ax-cx"
was evaluated.

All register contents are preserved by the debugger.  Therefore, neither
the choice of argument passing convention nor the called routine can
permanently change the register contents.  The called routine could,
however, have side effects such as modifying memory locations,
performing input/output, etc.


Disposition of the Return Value
───────────────────────────────
One of three possible actions can occur after the called routine returns
to the debugger.

   1. By default, the contents of the AX register (16-bit mode) or EAX
      register (32-bit mode), which is returned by the routine, are
      printed in the Dialogue window.  This default may be changed by
      using the Set Call command.
   2. A "/" may be used to indicate that the routine does not return any
      value in which case nothing is printed.
   3. A formatting string and list of expressions may be specified.  The
      syntax of print_list is similar to that of the Print command.  The
      expressions are evaluated and the results printed in the Dialogue
      window.

Example:
   DBG>call test1() /
   DBG>call test2( s, t ) ax, bx, cx
   DBG>call test3( a,b,c ){Results were %i,%i,%u}dx,ax,tag

In the first line of the above example, the routine does not return any
useful information in the AX register so we suppress the printing of
this register.  In the second line, the contents of the AX, BX and CX
registers are displayed with default formatting.  In the third line, the
contents of the DX and AX registers and the variable "tag" are displayed
using the specified formatting string.  See the description of the Print
command for more information on formatting strings.

Suppose that we want to update some of the registers in our current
register set with values returned by the routine that we call.

Example:
   DBG>call/far test() _ax=ax, _bx=bx;/ax=_ax;/bx=_bx

In the above example, we call the routine "test" using a "far" call.
Since register contents are unaffected by the call, we assign the values
returned in the AX and BX registers to the variables _ax and _bx.
Subsequent debugger commands assign these saved values to the AX and BX
registers in our current register set.  VIDEO allows us to define new
variables simply by specifying a unique name and then assigning a value
to it.

In the next example, we illustrate how to call a BIOS routine in 16-bit
"real" mode.

Example:
   DBG>c/int %0:(4*0x10) (/ah 3, /bh 0) {ct=%x,rc=%x}cx,dx

In the above example, we call the IBM BIOS "Video I/O" interrupt routine
(INT 0x10) to obtain the current cursor type and position (AH=3) for
video page 0 (BH=0).  The % operator yields the segment:offset pair
stored at locations 0:40 through 0:43.  The cursor type is returned in
the "CX" register and the cursor row and column are returned in the "DX"
register; hence we ask the debugger to display the contents of both
registers in hexadecimal format.
::::COMMAND_FILES
The following sections describe the command files that are provided with
VIDEO.

Under DOS or OS/2 systems, you should ensure that the "BINB" directory
of the WATCOM compiler package is included in the PATH environment
variable.  This directory contains the command files provided with
VIDEO.  VIDEO uses the PATH environment variable to locate command
files.

Under QNX, the command files provided with VIDEO are usually located in
the "/etc/wvideo" directory.  The search order for command files is as
follows:

   1. the current directory,
   2. the paths listed in the WVIDEO_PATH environment variable,
   3. the path listed in the HOME environment variable, and, finally,
   4. the "/etc/wvideo" directory.

The INvoke or < command is used to execute the commands within a command
file.  The Set Implicit command can be used to turn automatic command
file invocation "on" or "off".  When it is "on", VIDEO will attempt to
invoke a command file when the command that is entered does not match
one of those in its command set.  For more information on command file
processing, see the description of the INvoke command under the topic
"INVOKE".

───────────────────────────────────────────────────────
Setup for an AutoCAD ADS (or ADI) Application (ads.dbg)
───────────────────────────────────────────────────────
Syntax: ads <symbol_file_name>

Synopsis: This command file sets up a debugging session for an AutoCAD
       ADS (or ADI) application.  The symbolic information is stored in
       "symbol_file_name".  You must make sure that the environment
       variable EXPDEBUG has been set to ADS (or ADI) before starting
       AutoCAD.

       Example:
          C>set expdebug=ads

       You may have to change two lines in the command file if AutoCAD
       loads the application at some location other than where this
       command file expects (CS=0xA4, DS=0x9C).  Change the following
       statement to the code segment address reported by AutoCAD when it
       loads the ADS (or ADI) application.

       Example:
          /_dbg@ads_code = 0xa4

       Change the following statement to the data segment address
       reported by AutoCAD when it loads the ADS (or ADI) application.

       Example:
          /_dbg@ads_data = 0x9c

       Consult the AutoCAD Development System - Programmer's Reference
       for more information on creating ADS applications.


──────────────────────────────────────
Create Large Assembly Window (asm.dbg)
──────────────────────────────────────
Syntax: asm

Synopsis: This command file creates an Assembly window that uses most of
       the screen.  The Register window is placed on the right side of
       the screen.  A Stack window is defined but not placed on the
       screen.  Small Source and Dialogue windows are also created.  The
       debugging level is set to "assembly".

─────────────────────────
Break on Count (bcnt.dbg)
─────────────────────────
Syntax: bcnt <count> <address>

Synopsis: This command file is used to break execution after "count"
       iterations at the specified "address".  The break point is
       cleared afterwards.

Example: bcnt 1000 StageD

       Execution is halted after the routine "StageD" has been called
       1000 times.


──────────────────
Break If (bif.dbg)
──────────────────
Syntax: bif <expr> <address>

Synopsis: This command file is used to break execution at the specified
       "address" when "expr" is true (non-zero result).

Example: bif {ax == 0} malloc

       bif {eax == 0} malloc

       Execution is halted whenever the "malloc" routine is called with
       a request for 0 bytes of storage.  Note that the argument is
       passed in register AX in 16-bit mode or EAX in 32-bit mode.


──────────────────────────
Count Breaks (cntbrks.dbg)
──────────────────────────
Syntax: cntbrks <address>

Synopsis: Count the number of times <address> is executed.

Example: cntbrks StageD

       The name of the variable that is created to tabulate the number
       of iterations is displayed on the screen.  This variable can be
       queried at any time with the VIDEO Print command.  When program
       execution is started with the Go command, each break results in
       the message "cnt$xxxx = n" being printed on the program screen.

──────────────────────────────────
Setup Window Colours (colours.dbg)
──────────────────────────────────
Syntax: colours

Synopsis: This command file sets the colours for the various debugger
       windows.  The selection can be tailored to your own needs.  The
       command file is invoked by the start-up "profile.dbg" command
       file whenever the debugger is run on a colour monitor.


──────────────────────
Fill Memory (fill.dbg)
──────────────────────
Syntax: fill <address> <value> <length>

Synopsis: This command file may be used to fill a region of memory with
       a specific value.  The starting address to fill is specified by
       <address>.  The byte value to fill with is specified by <value>.
       The number of bytes to fill is specified by <length>.

Example: fill es:0 ff 100

       Fill 256 bytes of memory starting at ES:0 with the value 0xFF.  A
       radix of 16 is assumed in this example.


─────────────────────────────────────────────
Setup for a FoxPro External Routine (fox.dbg)
─────────────────────────────────────────────
Syntax: fox <symbol_file_name>

Synopsis: This command file sets up a debugging session for a FoxPro
       External Routine.  The symbolic information is stored in
       "symbol_file_name".

       Make sure that you have coded a call to BreakPoint() in your
       external routine.  This call should be in the first segment.
       When starting VIDEO, specify the "RESERVESYM=nn" option unless
       you are debugging remotely.

       Example:
          C>wvideo /reserve=5 foxpro

Example: Start the external routine (e.g.,?  hello()).  The call to
       BreakPoint() causes entry into debugger.  To start symbolic
       debugging, enter a command similar to the following:

       Example:
          DBG>fox hello.plb

       Consult the FoxPro External Routine API document for more
       information on creating FoxPro External Routines.


────────────────────────────────────────────
Create Assembly and Source Windows (mix.dbg)
────────────────────────────────────────────
Syntax: mix

Synopsis: This command file creates two evenly-sized Source and Assembly
       windows that use up most of the screen.  The Register window is
       placed on the right side of the screen.  A Stack window is
       defined but not placed on the screen.  A small Dialogue window is
       also created.  The debugging level is set to "mix".


───────────────────────────────────────
VIDEO Initialization File (profile.dbg)
───────────────────────────────────────
Syntax: profile

Synopsis: This is the VIDEO initialization file.  It can be customized
       for your own needs.  As distributed, it performs the following
       initialization.

          1. The menu bar is turned on.

          2. The debugging level is set to "mix" which is source level
             debugging whenever possible and assembly level debugging
             when no source line information is available.

          3. The symbol name matching patterns are set to "*", "*_" and
             "_*".

          4. Automatic command file invocation is enabled.  Any time an
             unrecognized command is entered, the debugger will try to
             execute a command file with the same name and extension
             "DBG".

          5. Radix specifiers for decimal (0n), hexadecimal (0x) and
             octal (0) numbers are defined.

          6. Default colours for various windows are set up.

          7. Command, Register, Stack, Fpu, Dialogue, Memory and Thread
             window sizes are defined.  Window sizes are based upon the
             number of screen lines that are available on the screen.

             The "SRC" command file is invoked to place Source and
             Dialogue windows on the screen.

          8. "View", "src", "mix", "asm", and "flip" commands are added
             to the user-definable "User" pop-down menu.  Note that
             "src", "mix" and "asm" are the names of VIDEO command
             files.  For FORTRAN applications, "new;go fmain" is also
             added to the menus.  For C applications, "new;go main" is
             also added to the menus.

          9. Function key "F1" is defined such that a press will cause
             the "help" system to be invoked.

             Function key "F4" is defined to add and remove the FPU
             window to and from the screen with alternate presses.

             Function key "F5" is set to issue a "register -1" command
             when pressed.

             Function key "F6" is set to issue a "register +1" command
             when pressed.

             Function key "F7" is defined such that a press will cause
             an invocation of the "WIND" command file.  This key cycles
             through different sizes for the Source and Assembly windows
             by using the "SRC", "MIX" and "ASM" command files.

             Function key "F8" is defined such that alternate presses
             turn the menu bar on and off.

             Function key "F10" is defined to activate menu selection in
             the same way that pressing and releasing the Alt key would.

             Function key "Alt/F9" is defined such that a press will
             move the cursor to the Source window.

             Function key "Alt/F10" is defined such that a press will
             move the cursor to the Assembly window.

          10. Macro hot keys are defined for the Assembly window.  The
             following keys are defined:

                'G' {g}            Resume execution
                'g' {g dbg$code}   Continue execution to the
                                    currently highlighted line
                'i' {t/a/i}        Single-shot trace "into"
                'n' {t/a/n}        Single-shot trace "next"
                ' ' {t/a/o}        Single-shot trace "over"
                'b' {b dbg$code}   Set a break point at the
                                    currently highlighted line
                'c' {b/c/dbg$code} Remove a break point at the
                                    currently highlighted line

          11. Macro hot keys are defined for the Source window.  The
             following keys are defined:

                'v' {view}         View the source code for the
                                    current module
                'G' {g}            Resume execution
                'g' {g dbg$code}   Continue execution to the
                                    currently highlighted line
                'i' {t/s/i}        Single-shot trace "into"
                'n' {t/s/n}        Single-shot trace "next"
                ' ' {t/s/o}        Single-shot trace "over"
                'b' {b dbg$code}   Set a break point at the
                                    currently highlighted line
                'c' {b/c/dbg$code} Remove a break point at the
                                    currently highlighted line

          12. Macro hot keys are defined for the FPU window.  The
             following keys are defined:

                'b' {set fpu binary} Set the display mode to
                                    hexadecimal
                'd' {set fpu decimal} Set the display mode to
                                    decimal

          13. For FORTRAN applications, VIDEO will issue a "go fmain"
             command.  Otherwise, if the "main" entry point is defined
             then VIDEO will issue a "go main" command.

─────────────────────────────────────────
Set DOS Memory Control Block (resize.dbg)
─────────────────────────────────────────
Syntax: resize <new_size>

Synopsis: (DOS only) This command file sets the DOS memory control block
       containing the PSP to a new size.  The PSP value is recorded in
       the debugger variable _dbg@dbg$psp.  Before an application
       starts, DOS gives it all of the remaining memory.  Normally, the
       application should return to DOS that portion of memory which it
       does not use.  This command file can be used in the event that
       the application does not return unused memory to DOS and you wish
       to start up a subprocess by using the VIDEO SYSTEM command.  In
       this case, memory must be returned to DOS before a subprocess can
       be started.

Example: resize 0x1000

       Reset the memory control block containing the current PSP to 64K
       bytes.

┌──────────────────────────────────────────────────────────────────────┐
│ WARNING!  If an incorrect or inappropriate size is specified, the    │
│ computer system could hang.  Too small values will cause erratic     │
│ operation.                                                           │
└──────────────────────────────────────────────────────────────────────┘


────────────────────────────────────────
Return from Current Routine (return.dbg)
────────────────────────────────────────
Syntax: return

Synopsis: This command file may be used to return from the current
       routine.  Execution of the application is advanced until a RETURN
       instruction is encountered.  Execution is then advanced by an
       additional instruction in order to return to the calling routine.


─────────────────────────────────────
Slow Motion Code Animation (slow.dbg)
─────────────────────────────────────
Syntax: slow <delay>

Synopsis: This command file can be used to perform slow motion execution
       of a program.  The <delay> value must be specified.  The larger
       the value for <delay>, the slower the program will execute.

─────────────────────────────
Save Current Setup (save.dbg)
─────────────────────────────
Syntax: save

Synopsis: Creates a file called setup.dbg which contains the debugger
       commands required to recreate the current debugger configuration.


────────────────────────────────────
Create Large Source Window (src.dbg)
────────────────────────────────────
Syntax: src

Synopsis: This command file creates a Source window that uses most of
       the screen.  A small Dialogue window is also created.  Any
       Register or Stack windows are removed from the screen.  The
       Assembly window is hidden under the Dialogue window.  The
       debugging level is set to "source".  The command file is invoked
       by the start-up "profile.dbg" command file.


───────────────────────────────────────
Define Function Key Toggle (toggle.dbg)
───────────────────────────────────────
Syntax: toggle <pfkey_number> <command_string_1> <command_string_2>

Synopsis: This command file sets up a PF key to alternate between two
       commands.

Example: toggle 10 {set menu on} {set menu off}

       Function key "F10" is defined to toggle the menu bar on and off.


──────────────────────────────────────
View Output from CALL Command (vc.dbg)
──────────────────────────────────────
Syntax: vc <call_address_and_arguments>

Synopsis: This command file uses the View command to examine the
       standard output from a routine called by the Call command.  The
       file "stdout.tmp" is created.

Example: vc DumpTree( HeadNode )

─────────────────────────────────────
View Source Code for Routine (vr.dbg)
─────────────────────────────────────
Syntax: vr <routine_name>

Synopsis: This command file examines the source code for a given routine
       by using the View command.

Example: vr main


─────────────────────────────────────────────
Window Management Utility Function (wind.dbg)
─────────────────────────────────────────────
Syntax: wind

Synopsis: This command file invokes one of the "SRC", "ASM", or "MIX"
       command files depending on the state of the _dbg@dbg$wind_split
       variable.  It is primarily a utility command file that is invoked
       by other command files or function keys.
::::C_OPERATORS
VIDEO supports most C operators and includes an additional set of
operators for convenience.  The WATCOM C Language Reference manual
describes many of these operators.

The syntax for VIDEO expressions is similar to that of the C programming
language.  Operators are presented in order of precedence, from lowest
to highest.  Operators on the same line have the same priority.

                                           Lowest Priority
   Assignment Operators
       =  +=  -=  *=  /=  %=  &=  |=  ^=  <<=  >>=
   Logical Operators
       ||
       &&
   Bit Operators
       |
       ^
       &
   Relational Operators
       ==  !=
       <   <=   <   >=
   Shift Operators
       <<  >>
   Arithmetic Operators
       +  -
       *  /  %
   Unary Operators
       +  -  ~  !  ++  --  &  *  %
       sizeof unary_expr
       sizeof(type_name)
       (type_name) unary_expr
       [type_name] unary_expr
       ?
   Binary Address Operator
       :
                                           Highest Priority

Parentheses can be used to order the evaluation of an expression.

In addition to the operators listed above, a number of primary
expression operators are supported.  These operators are used in
identifying the object to be operated upon.

[]     subscripting, substringing

()     function call

.      field selection

->     field selection using a pointer

The following sections describe the operators presented above.

Assignment Operators for the C Grammar
──────────────────────────────────────

=      Assignment:  The value on the right is assigned to the object on
       the left.

+=     Additive assignment:  The value of the object on the left is
       augmented by the value on the right.

-=     Subtractive assignment:  The value of the object on the left is
       reduced by the value on the right.

*=     Multiplicative assignment:  The value of the object on the left
       is multiplied by the value on the right.

/=     Division assignment:  The value of the object on the left is
       divided by the value on the right.

%=     Modulus assignment:  The object on the left is updated with
       MOD(left,right).  The result is the remainder when the value of
       the object on the left is divided by the value on the right.

&=     Bit-wise AND:  The bits in the object on the left are ANDed with
       the bits of the value on the right.

|=     Bit-wise inclusive OR:  The bits in the object on the left are
       ORed with the bits of the value on the right.

^=     Bit-wise exclusive OR:  The bits in the object on the left are
       exclusively ORed with the bits of the value on the right.

<<=    Left shift:  The bits in the object on the left are shifted to
       the left by the amount of the value on the right.

>>=    Right shift:  The bits in the object on the left are shifted to
       the right by the amount of the value on the right.  If the object
       on the left is described as unsigned, the vacated high-order bits
       are zeroed.  If the object on the left is described as signed,
       the sign bit is propagated through the vacated high-order bits.
       VIDEO treats registers as unsigned items.

Logical Operators for the C Grammar
───────────────────────────────────

&&     Logical conjunction:  The logical AND of the value on the left
       and the value on the right is produced.  If either of the values
       on the left or right is equal to 0 then the result is 0;
       otherwise the result is 1.

||     Logical inclusive disjunction:  The logical OR of the value on
       the left and the value on the right is produced.  If either of
       the values on the left or right is not equal to 0 then the result
       is 1; otherwise the result is 0.  If the value on the left is not
       equal to 0 then the expression on the right is not evaluated
       (this is known as short-circuit expression evaluation).


Bit Operators for the C Grammar
───────────────────────────────

&      Bit-wise AND:  The bits of the value on the left and the value on
       the right are ANDed.

|      Bit-wise OR:  The bits of the value on the left and the value on
       the right are ORed.

^      Bit-wise exclusive OR:  The bits of the value on the left and the
       value on the right are exclusively ORed.


Relational Operators for the C Grammar
──────────────────────────────────────

==     Equal:  If the value on the left is equal to the value on the
       right then the result is 1; otherwise the result is 0.

!=     Not equal:  If the value on the left is not equal to the value on
       the right then the result is 1; otherwise the result is 0.

<      Less than:  If the value on the left is less than the value on
       the right then the result is 1; otherwise the result is 0.

<=     Less than or equal:  If the value on the left is less than or
       equal to the value on the right then the result is 1; otherwise
       the result is 0.

>      Greater than:  If the value on the left is greater than the value
       on the right then the result is 1; otherwise the result is 0.

>=     Greater than or equal:  If the value on the left is greater than
       or equal to the value on the right then the result is 1;
       otherwise the result is 0.

Arithmetic/Logical Shift Operators for the C Grammar
────────────────────────────────────────────────────

<<     Left shift:  The bits of the value on the left are shifted to the
       left by the amount described by the value on the right.

>>     Right shift:  The bits of the value on the left are shifted to
       the right by the amount described by the value on the right.  If
       the object on the left is described as unsigned, the vacated
       high-order bits are zeroed.  If the object on the left is
       described as signed, the sign bit is propagated through the
       vacated high-order bits.  VIDEO treats registers as unsigned
       items.


Binary Arithmetic Operators for the C Grammar
─────────────────────────────────────────────

+      Addition:  The value on the right is added to the value on the
       left.

_      Subtraction:  The value on the right is subtracted from the value
       on the left.

*      Multiplication:  The value on the left is multiplied by the value
       on the right.

/      Division:  The value on the left is divided by the value on the
       right.

%      Modulus:  The modulus of the value on the left with respect to
       the value on the right is produced.  The result is the remainder
       when the value on the left is divided by the value on the right.


Unary Arithmetic Operators for the C Grammar
────────────────────────────────────────────

+      Plus:  The result is the value on the right.

_      Minus:  The result is the negation of the value on the right.

~      Bit-wise complement:  The result is the bit-wise complement of
       the value on the right.

!      Logical complement:  If the value on the right is equal to 0 then
       the result is 1; otherwise it is 0.

++     Increment:  Both prefix and postfix operators are supported.  If
       the object is on the right, it is pre-incremented by 1 (e.g.,
       ++x).  If the object is on the left, it is post-incremented by 1
       (e.g., x++).

_ _    Decrement:  Both prefix and postfix operators are supported.  If
       the object is on the right, it is pre-decremented by 1 (e.g.,
       --x).  If the object is on the left, it is post-decremented by 1
       (e.g., x--).

&      Address of:  The result is the address (segment:offset) of the
       object on the right (e.g., &main).

*      Points:  The result is the value stored at the location addressed
       by the value on the right (e.g., *(ds:100), *string.loc).  In the
       absence of typing information, the value on the right is treated
       as a pointer into the stack segment and a near pointer is
       produced.

                (SS:00FE) = FFFF
          var:  (SS:0100) = 0152
                (SS:0102) = 1240
                (SS:0104) = EEEE

       In the following example, memory locations are displayed starting
       at DS:152 for 16-bit mode and at DS:12400152 for 32-bit mode.

       Example:
          DBG>examine/byte *100

%      Value at address:  The result is the value stored at the location
       addressed by the value on the right (e.g., %(ds:100),
       %string.loc).  In the absence of typing information, the value on
       the right is treated as a pointer into the stack segment and a
       far pointer is produced.

                (SS:00FE) = FFFF
          var:  (SS:0100) = 0152
                (SS:0102) = 1240
                (SS:0104) = EEEE

       In the following example, memory locations are displayed starting
       at 1240:1052 for 16-bit mode and at EEEE:12400152 for 32-bit
       mode.

       Example:
          DBG>examine/byte %100

       Note that this operator is not found in the C programming
       language.


Special Unary Operators for the C Grammar
─────────────────────────────────────────

sizeof unary_expression

       Example:
          DBG>print sizeof tyme
          2 (or 4 in 32-bit mode)
          DBG>print sizeof *tyme
          18

sizeof(type_name)

       Example:
          DBG>print sizeof( struct tm )
          18

(type_name) unary_expression The type conversion operator (type_name) is
       used to convert an item from one type to another.  The following
       describes the syntax of "type_name".

          type_name ::= type_spec { [ "near" | "far" | "huge" ] "*" }
          type_spec ::= typedef_name
                          |   "struct" structure_tag
                          |   "union"  union_tag
                          |   "enum"   enum_tag
                          |   scalar_type { scalar_type }
          scalar_type ::= "char" | "int" | "float" | "double"
                          |   "short" | "long" | "signed" | "unsigned"

       Example:
          DBG>print (float) 4
          4.
          DBG>print (int) 3.1415926
          3

[type_name] unary_expression You can force the debugger to treat a
       memory reference as a particular type of value by using a type
       coercion operator.  A type specification is placed inside
       brackets as shown above.  The basic types are char (character, 8
       bits), short (short integer, 16 bits), long (long integer, 32
       bits), float (single-precision floating-point, 32 bits), and
       double (double-precision floating-point, 64 bits).  Unless
       qualified by the short or long keyword, the int type will be 16
       bits in 16-bit applications and 32 bits in 32-bit applications
       (386 and 486 systems).  The character, short integer and long
       integer types may be treated as signed or unsigned items.  The
       default for the character type is unsigned.  The default for the
       integer types is signed.

       Example:
          [char]                  (default unsigned)
          [signed char]
          [unsigned char]
          [int]                   (default is signed)
          [short]                 (default is signed)
          [short int]             (default is signed)
          [signed short int]
          [long]                  (default is signed)
          [long int]              (default is signed)
          [signed long]
          [unsigned long int]
          [float]
          [double]

       Note that it is unnecessary to specify the int keyword when short
       or long are specified.

?      Existence test:  The "?" unary operator may be used to test for
       the existence of a symbol.

       Example:
          DBG>print ?id

       The result of this expression is 1 if "id" is a symbol known to
       VIDEO and 0 otherwise.  If the symbol does not exist in the
       current scope then it must be qualified with its module name.
       Automatic symbols exist only in the current function.


Binary Address Operator for the C Grammar
─────────────────────────────────────────

:      Memory locations can be referenced by using the binary ":"
       operator and a combination of constants, register names, and
       symbol names.  In the Intel 80x86 architecture, a memory
       reference requires a segment and offset specification.  A memory
       reference using the ":" operator takes the following form:

          segment:offset

       The elements segment and offset can be expressions.

       Example:
          (ES):(DI+100)
          (SS):(SP-20)


Primary Expression Operators for the C Grammar
──────────────────────────────────────────────

[]     Elements of an array can be identified using subscript
       expressions.  Consider the following 3-dimensional array defined
       in the "C" language.

       Example:
          char *ProcessorType[2][4][2] =
              { { { "Intel 8086",   "Intel 8088"  },
                  { "Intel 80186",  "Intel 80188" },
                  { "Intel 80286",  "unknown" },
                  { "Intel 80386",  "unknown" } },

                { { "NEC V30",      "NEC V20" },
                  { "unknown",      "unknown" },
                  { "unknown",      "unknown" },
                  { "unknown",      "unknown" } } };

       This array can be viewed as two layers of rectangular matrices of
       4 rows by 2 columns.  The array elements are all pointers to
       string values.

       By using a subscript expression, specific slices of an array can
       be displayed.  To see only the values of the first layer, the
       following command can be issued.

       Example:
          DBG>print processortype[0]
          {[0]={[0]=0x0024, [1]=0x002F},
           [1]={[0]=0x003A, [1]=0x0046},
           [2]={[0]=0x0052, [1]=0x005E},
           [3]={[0]=0x0066, [1]=0x005E}}

       The values shown are the addresses of the string values.

       To see only the first row of the first layer, the following
       command can be issued.

       Example:
          DBG>print processortype[0][0]
          {[0]=0x0024, [1]=0x002F}

       To see the second row of the first layer, the following command
       can be issued.

       Example:
          DBG>print processortype[0][1]
          {[0]=0x003A, [1]=0x0046}

       To see the value of a specific entry in a matrix, all the indices
       can be specified.

       Example:
          DBG>print {%s} processortype[0][0][0]
          Intel 8086
          DBG>print {%s} processortype[0][0][1]
          Intel 8088
          DBG>print {%s} processortype[0][1][0]
          Intel 80186

       In the above examples, we use the "%s" format specifier to
       display the string values.

()     The function call operators appear to the right of a symbol name
       and identify a function call in an expression.  The parentheses
       can contain arguments.

       Example:
          DBG>print ClearScreen()
          DBG>print PosCursor( 10, 20 )
          DBG>print Line( 15, 1, 30, '-', '+', '-' )

.      The "." operator indicates field selection in a structure.  In
       the following example, tyme2 is a structure and tm_year is a
       field in the structure.

       Example:
          DBG>print tyme2.tm_year

->     The "->" operator indicates field selection when using a pointer
       to a structure.  In the following example, tyme is the pointer
       and tm_year is a field in the structure to which it points.

       Example:
          DBG>print tyme->tm_year
::::DISPLAY

┌──────────────────────────────────────────────────────────────────────┐
│ Display                                                              │
│     Assembly [status] [title] [window_coord]                         │
│     Command  [status] [title] [window_coord] [cmd_list]              │
│     Dialogue [status] [title] [window_coord]                         │
│     Fpu      [status] [title] [window_coord]                         │
│     Memory   [status] [title] [window_coord] [mem_loc]               │
│     Prompt   [status] [title] [line_number]                          │
│     Register [status] [title] [window_coord]                         │
│     SOurce   [status] [title] [window_coord]                         │
│     STack    [status] [title] [window_coord]                         │
│     Thread   [status] [title] [window_coord]                         │
└──────────────────────────────────────────────────────────────────────┘

The Display command is used to create or remove output windows for
various displays that the debugger can provide.  For each window, you
may specify a window status, a title, the starting line number of the
window and, for those windows which may vary in size, the ending line
number.  VIDEO windows are described under the topic "WINDOWS".

When no window name is specified then all windows are updated.  This
command may be used to recreate window displays if the user's
application has overwritten them.  It may also be used in command lists
to update the display.

Window Titles
─────────────
Each window that is created with the Display command may have a title.
The title is specified by placing a string of characters inside curly
braces and is formally described as follows:

   title ::= "{" text "}"

An asterisk (*) may be specified as part of the string and represents a
place holder for the current module name.

Example:
   DBG>display assembly {Assembly: *}

In the above example, the Assembly window is given the title "Assembly:
*".  If the current module name was "hello" then the title would appear
at the top of the Assembly window as follows:

   ==| Assembly: hello |======================

To remove the title from a window, simply specify a pair of empty
braces.

Example:
   DBG>display assembly {}


Window Placement
────────────────
Starting at the top of the screen, output lines are numbered
consecutively starting with 1.  Columns are numbered from left to right
starting with 1.  It is possible to define windows that overlap other
windows thereby partially obscuring the contents of the overlapped
window.

Window coordinates are specified in terms of a top row, a bottom row, a
left column, and a right column.

   window_coord ::= [top][","[bottom][","[left][","right]]]

The top, bottom, left and right items are expressions which are always
evaluated with a radix of 10, regardless of the current default radix
for numbers.

Example:
   DBG>display assembly 3,20,1,80

In the above example, the Assembly window is defined to occupy lines 3
through 20 and columns 1 through 80.

Example:
   DBG>display assembly {Assembly: *} 3,20,1,80

This example is similar to the previous one but a window title is also
specified.

Example:
   DBG>display assembly ,,8,60

In this example, we redefine the starting and ending columns for the
Assembly window to be 8 and 60.


Window Disposition
──────────────────
The disposition of each window that is created with the Display command
may be specified using one of the following status qualifiers.

/Open  The window is created and placed on the screen.

       Example:
          DBG>dis assembly /open {Asm: *} 13,19,1,71

       This is the default action when creating a window hence it is not
       necessary to specify this qualifier.

/Close A window that is currently on the screen can be removed by
       specifying the /Close qualifier.  The debugger will not let you
       remove the Dialogue and Prompt windows but they can be moved to
       different positions on the screen.

       Example:
          DBG>display assembly /close

       In the above example, the Assembly window is removed from the
       screen.

       A window can be created but not placed on the screen.

       Example:
          DBG>display fpu /close {FPU} 3,13,1,64

       It may be placed on the screen at a later time using the Display
       command and it will not be necessary to respecify the window
       title or coordinates.

/Zoom  The window is created and immediately displayed on the screen
       using the full dimensions of the screen.

       Example:
          DBG>display source /zoom

       If the window is already on the screen then its size will
       alternate between its defined size and the full dimensions of the
       screen.


Window Attributes
─────────────────
Various items in the window are displayed with special attributes.  See
the description of the Paint command for a discussion of "plain",
"active", "standout", "title" and "gadget" attributes.


The Assembly Window
───────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Display Assembly [status] [title] [window_coord]                     │
└──────────────────────────────────────────────────────────────────────┘

The debugger displays assembly instructions for the current code
location in this window.  If the Code Segment and Instruction Pointer
registers (CS:IP or CS:EIP) point to an instruction visible in the
Assembly window then the line containing that instruction is displayed
in "active" attributes.  When examining assembly instructions, one line
is designated as the current line and is displayed in "standout"
attributes.  The Source window, if present, is kept synchronized with
the Assembly window provided that source information is available.


The Command Window
──────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Display Command [status] [title] [window_coord] [cmd_list]           │
└──────────────────────────────────────────────────────────────────────┘

The Command window can be used to display the results of one or more
commands which you wish to have evaluated each time control returns to
the debugger.

The command list that follows the command is defined as follows:

   cmd_list ::= "{" [cmd] { ";" [cmd] } "}"

Example:
   DBG>display command 3, 8 {e es:bx,.+10,10,4; reg}

The output from commands such as:

Example:
   DBG>e es:bx,.+10,10,4
   DBG>reg

are normally displayed in other windows.  The list of commands that are
specified when the Command window is created is executed and the results
are displayed in the command window.  The commands are re-executed and
the results are displayed in the Command window whenever:

   1. the debugger is entered,
   2. one of the commands Display or Display Command is issued, or
   3. the Command window is selected (by using the mouse or tab keys).

This facility provides a mechanism for watching the values of one or
more variables change (see also the Print /Window command).


The Dialogue Window
───────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Display Dialogue [status] [title] [window_coord]                     │
└──────────────────────────────────────────────────────────────────────┘

By default, the debugger displays responses to commands in this window.
When one of the other windows is not present on the screen, the output
normally destined for that window is displayed in the Dialogue window.


The FPU Window
──────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Display Fpu [status] [title] [window_coord]                          │
└──────────────────────────────────────────────────────────────────────┘

The contents of the 80x87 numeric data processor (math coprocessor)
registers and status flags are displayed in this window.  When the
contents of a register have changed from the last time that the debugger
was entered, it is displayed in "standout" attributes.


The Memory Window
─────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Display Memory [status] [title] [window_coord] [mem_loc]             │
└──────────────────────────────────────────────────────────────────────┘

A portion of memory is displayed in this window.  When the Memory window
is active, the currently selected memory location is displayed in
"active" attributes.  Memory window "hot spots" (e.g., BYTE ) are
displayed in "standout" attributes.  All other items are displayed in
"plain" attributes.

Example:
   DBG>display memory /open {Low Mem} 3,9,,,ds:36

In the above example, memory starting at location DS:36 is displayed in
a Memory window that runs from lines 3 through 9 and columns 1 through
80.

Example:
   DBG>display memory /close

In the above example, the Memory window is removed from the screen.


The Prompt Window
─────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Display Prompt [status] [title] [line_number]                        │
└──────────────────────────────────────────────────────────────────────┘

The debugger command input prompt "DBG>" is displayed in a window that
is one line high.  The prompt window is used to enter command lines.

In multiple execution thread applications, the "DBG>" prompt is replaced
by a prompt that indicates the current thread.  The form of the prompt
is "ddd>" where "ddd" is the thread identification number.

Example:
   002>


The Register Window
───────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Display Register [status] [title] [window_coord]                     │
└──────────────────────────────────────────────────────────────────────┘

The current contents of the 80x86 registers are displayed in a window.
When the contents of a register have changed from the last time that the
debugger was entered, it is displayed in "standout" attributes.  An
exception to this rule is the Instruction Pointer (IP, EIP) register
which is only displayed in "standout" attributes when its value changes
because some type of branch or call instruction was executed.

If a register set other than register set 0 is displayed, then the
register set number is displayed in brackets (e.g., [1]) with "active"
attributes (see the description of the Register command).


The Source Window
─────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Display SOurce [status] [title] [window_coord]                       │
└──────────────────────────────────────────────────────────────────────┘

If program source code information is available for the current code
location then it will be displayed in this window.  If the Code Segment
and Instruction Pointer registers (CS:IP or CS:EIP) point to a source
line visible in the Source window then the line is displayed in "active"
attributes.  When examining source code, one line is designated as the
current line and is displayed in "standout" attributes.  The Assembly
window, if present, is kept synchronized with the Source window.


The Stack Window
────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Display STack [status] [title] [window_coord]                        │
└──────────────────────────────────────────────────────────────────────┘

A portion of the execution stack is displayed in this window.  If the
Base Pointer (BP or EBP) register points to a visible byte, word, or
doubleword on the stack, the byte, word, or doubleword is displayed in
"standout" attributes.  All other words are displayed in "plain"
attributes.


The Thread Window
─────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Display Thread [status] [title] [window_coord]                       │
└──────────────────────────────────────────────────────────────────────┘

The Thread window is used to display the identification number, state
and name of all program execution threads.  Whenever the debugger is
entered, the currently executing thread is displayed in "active"
attributes.  The currently selected thread is displayed in "standout"
attributes.  All other items are displayed in "plain" attributes.

There are 3 entries in the Thread window.  The first entry is the thread
identification number or thread ID.  The second entry is the thread
state which may be one of "runnable" or "frozen".  The third entry is
the thread name which is applicable to NetWare 386 server tasks only.

Under DOS or QNX, there is only one execution thread so there is only
one entry in the Thread window.  Under OS/2 or NetWare 386, there may be
several execution threads so there may be be several entries in the
Thread window.

Example:
   DBG>display thread /open {Threads} 14,19,20,50

In the above example, execution thread information is displayed in a
Thread window that runs from lines 14 through 19 and columns 20 through
50.

Example:
   DBG>display thread /close

In the above example, the Thread window is removed from the screen.
::::DO
┌──────────────────────────────────────────────────────────────────────┐
│ DO      expr                                                         │
│ /                                                                    │
└──────────────────────────────────────────────────────────────────────┘

The DO or / command evaluates an expression and discards the result.  It
is useful for assigning new values to registers and variables.  The
expression expr can involve registers, application variables and
user-defined variables.  The operations possible are patterned after
those available in the C and FORTRAN 77 programming languages.
Expressions are fully discussed in the chapter entitled "VIDEO
Expression Handling".

Example:
   DBG>do ax=1
   DBG>/ax=1

The above example illustrates two identical ways to set the contents of
the AX register to 1.

Example:
   DBG>/myvar=di-bx+1

The variable myvar is defined with the value resulting from subtracting
the contents of the BX register from the contents of the DI register and
then adding 1.

Example:
   DBG>/oldsi=si++

The variable oldsi is defined with the current contents of the SI
register.  The current contents of the SI register are then incremented
by 1 (the C-like "++" operator increments the value of the variable).
Variables such as oldsi need not be defined within the application.
VIDEO permits the dynamic creation of new variables which will only
exist for the duration of the debug session.  These user-defined
variables can be used to retain information as we have shown in the
above example.
::::DOS_EXTENDER
Debugging 32-bit DOS Extender Applications
──────────────────────────────────────────

Introduction
────────────

VIDEO supports debugging of 32-bit applications developed with WATCOM
C/386, WATCOM FORTRAN 77/386, and assembly language.  A DOS Extender
must be used to run the application.  The following DOS Extenders are
supported.

DOS/4GW
       a DOS extender from Rational Systems, Inc.  DOS/4GW is a subset
       of Rational Systems' DOS/4G product.  DOS/4GW is customized for
       use with WATCOM C/386 and WATCOM FORTRAN 77/386 and is included
       in these packages.

OS/386
       (version 2.1 or later) a DOS Extender from ERGO Computing, Inc.

386|DOS-Extender
       (version 2.2d or later) a DOS Extender from Phar Lap Software,
       Inc.


VIDEO Command Line Format for DOS Extenders
───────────────────────────────────────────

The interface between VIDEO and the operating system/DOS Extender is
contained in a special "trap" file.  The trap file is specified to VIDEO
using the "TRAP" option.

┌──────────────────────────────────────────────────────────────────────┐
│ WVIDEO /TRap=trap_file[;trap_parm] [:sym_file] file_spec [cmd_line]  │
└──────────────────────────────────────────────────────────────────────┘

The TRap option must be specified when debugging applications that
require a 32-bit DOS Extender.  For convenience, this option can be
specified through use of the WVIDEO environment variable.

┌──────────────────────────────────────────────────────────────────────┐
│ set WVIDEO=/TRap#trap_file[;trap_parm]                               │
└──────────────────────────────────────────────────────────────────────┘

When trap_parm is specified and it contains blank characters, the entire
parameter must be placed within braces (e.g., /trap=pls;{-minr 128}).

You must specify the name of one of the DOS Extender "trap" files
provided with VIDEO.  The file extension defaults to ".TRP".

RSI.TRP This interface module supports debugging on the local computer
       system running the Rational Systems, Inc.  "DOS/4GW" DOS extender
       (which is included in the WATCOM C/386 and WATCOM FORTRAN 77/386
       packages).  The optional "trap_parm" is ignored.

ECS.TRP This interface module supports debugging on the local computer
       system running the ERGO Computing, Inc.  "OS/386" DOS Extender.
       The optional "trap_parm" is ignored.

PLS.TRP This interface module supports debugging on the local computer
       system running the Phar Lap Software, Inc.  386|DOS-Extender.
       The optional "trap_parm" is passed on to the DOS Extender
       "RUN386" as command line switches.

┌──────────────────────────────────────────────────────────────────────┐
│ Note:  If you do not specify a trap file, the default trap file      │
│ "STD.TRP" will be loaded.  This interface module supports debugging  │
│ on the local computer system running DOS.  No 32-bit DOS Extender    │
│ debugging is possible.                                               │
└──────────────────────────────────────────────────────────────────────┘

The following diagram illustrates how memory might be organized when
debugging a 32-bit DOS Extender application.

           |                |
           |                |
           +----------------+
           |                |
           |      32-bit    |
           |   Application  |
   109C4   +----------------+
           |                |
           |                |
           |                |
    7E6E   +----------------+
           |  trap handler  |
           |    ECS.TRP<----|--+
    7B27   +-------|--------+  |
           |       |        |  |
           |     WVIDEO     |  |
           |                |  |
    47A4   +----------------+  |
           |                |  |
           |     OS/386     |  |
           |  DOS Extender<-|--+
           |                |
    262C   +----------------+
           |                |
           |                |
           |                |
           |                |
    0000   +----------------+


Using the Rational 32-bit DOS Extender
──────────────────────────────────────

When using the Rational Systems, Inc.  DOS extender, the "DOS4GW.EXE"
file must be located in one of the directories listed in the DOS PATH
environment variable.  The "DOS4GW.EXE" file will usually be stored in
the "BIN" directory of the WATCOM compiler package.

┌──────────────────────────────────────────────────────────────────────┐
│ C>WVIDEO/TRap=RSI [:sym_file] file_spec [cmd_line]                   │
└──────────────────────────────────────────────────────────────────────┘

The /TRap=RSI option must be specified when debugging applications that
are to be run under the "DOS/4GW" DOS extender.  The "RSI.TRP" file will
usually be stored in the "BIN" directory of the WATCOM compiler package.
You should ensure that this "BIN" directory is included in the DOS PATH
environment variable.  Otherwise, you must specify the full path name
for the trap file.

Example:
   C>wvideo /trap=rsi hello
     or
   C>set wvideo=/trap#rsi
   C>wvideo hello


Using the ERGO 32-bit DOS Extender
──────────────────────────────────

When using the ERGO Computing, Inc.  DOS Extender, the "OS386" program
must be run first.

┌──────────────────────────────────────────────────────────────────────┐
│ C>OS386                                                              │
│ C>WVIDEO/TRap=ECS [:sym_file] file_spec [cmd_line]                   │
└──────────────────────────────────────────────────────────────────────┘

The /TRap=ECS option must be specified when debugging applications that
are to be run under the "OS386" DOS Extender.  The "ECS.TRP" file will
usually be stored in the "BIN" directory of the WATCOM compiler package.
You should ensure that this "BIN" directory is included in the DOS PATH
environment variable.  Otherwise, you must specify the full path name
for the trap file.

Example:
   C>wvideo /trap=ecs hello
     or
   C>set wvideo=/trap#ecs
   C>wvideo hello


Using the Phar Lap 32-bit DOS Extender
──────────────────────────────────────

When using the Phar Lap Software, Inc.  DOS Extender, the "RUN386.EXE"
and "PLSHELP.EXP" files must be located in one of the directories listed
in the DOS PATH environment variable.

┌──────────────────────────────────────────────────────────────────────┐
│ C>WVIDEO/TRap=PLS[;trap_parm] [:sym_file] file_spec [cmd_line]       │
└──────────────────────────────────────────────────────────────────────┘

The /TRap=PLS option must be specified when debugging applications that
are to be run under the Phar Lap DOS Extender.  The "PLS.TRP" and
"PLSHELP.EXP" files will usually be stored in the "BIN" directory of the
WATCOM compiler package.  You should ensure that this "BIN" directory is
included in the DOS PATH environment variable.  Otherwise, you must
specify the full path name for the trap file.

The optional "trap_parm" is passed on to the DOS Extender "RUN386" as
command line switches.  When trap_parm is specified and it contains
blank characters, the entire parameter must be placed within braces
(e.g., /trap=pls;{-minr 128}).

Example:
   C>wvideo /trap=pls;{-maxreal 512} hello
     or
   C>set wvideo=/trap#pls;{-maxreal 512}
   C>wvideo hello
::::DOS_STARTUP
┌──────────────────────────────────────────────────────────────────────┐
│ WVIDEO [options] [:sym_file] file_spec [cmd_line]                    │
└──────────────────────────────────────────────────────────────────────┘

The square brackets [ ] denote items which are optional.

WVIDEO is the program name for VIDEO.

options is a list of valid VIDEO options, each preceded by a dash ("-")
       or a slash ("/").  Options may be specified in any order.

sym_file is an optional symbolic debugging information file
       specification.  The specification must be preceded by a colon
       (":").  For DOS, the syntax of sym_file is:

       [d:][path]filename[.ext]

       The default file extension of the symbol file is ".SYM".

       The symbolic information file can be produced by the WATCOM
       Linker WLINK or by the WATCOM Strip Utility WSTRIP.

file_spec is the file name of the file to be loaded into memory.  For
       DOS, the syntax of file_spec is:

       [d:][path]filename[.ext]

       d:     is an optional drive specification such as "A:", "B:",
              etc.  If not specified, the default drive is assumed.

       path   is an optional path specification such as "\UTILS\BIN\".

       filename is the file name of the file to be loaded into memory.

       ext    is the file extension of the file to be loaded into
              memory.  A null file extension may be specified by typing
              the period "." but not the extension.  If no file
              extension is specified (i.e., both the period and
              extension are omitted) then VIDEO will attempt to load an
              executable image file using, in succession, the following
              extensions.

              For DOS, the search order is:  .COM, .EXE

              For the Ergo DOS Extender, the search order is:  .EXP,
              .PLX, .EXE

              For the Phar Lap DOS Extender, the search order is:  .EXP,
              .EXE

              For NetWare 386, the search order is:  .NLM, .DSK, .LAN

cmd_line is an optional command line which will be passed on to the
       application.

If both drive and path are omitted, VIDEO will first attempt to locate
the file in the current directory of the default drive.  If this fails,
VIDEO will search for the file in each path listed in the PATH
environment string.

Command Line Options
────────────────────

┌──────────────────────────────────────────────────────────────────────┐
│                                                                      │
│     [/Monochrome | /Color | /Colour | /Ega43 | /Vga50]               │
│     /Overwrite | /Page | /Swap | /Two                                │
│     /Checksize=space                                                 │
│     /Dynamic=space                                                   │
│     /NOFpu                                                           │
│     /Invoke=file_spec                                                │
│     /NOInvoke                                                        │
│     /NOMouse                                                         │
│     /Registers=number                                                │
│     /REMotefiles                                                     │
│     /REServesym=space                                                │
│     /NOSNow                                                          │
│     /NOSymbols                                                       │
│     /TRap=trap_file[;trap_parm]                                      │
└──────────────────────────────────────────────────────────────────────┘

Options may be specified in any order.  Short forms may be specified for
options and are shown above in capital letters.  If "space" is suffixed
with the letter "K" then "space" refers to multiples of 1K bytes (1024
bytes).  If "space" is suffixed with the letter "B" then "space" refers
to the number of bytes.  If no suffix is specified and "space" is a
number less than 1000 then "space" is assumed to refer to multiples of
1K bytes (1024 bytes); otherwise it refers to the number of bytes.

Display Selection

/Monochrome When two display devices are present in the system, this
       option indicates that the Monochrome display is to be used as the
       debugger's output device.  This option is used in conjunction
       with the Two option described below.

/Color, /Colour When two display devices are present in the system, this
       option indicates that the Colour display is to be used as the
       debugger's output device.  This option is used in conjunction
       with the Two option described below.

/Ega43 When an Enhanced Graphics Adapter (EGA) is present, 43 lines of
       output are displayed.

/Vga50 When an Video Graphics Array (VGA) is present, 50 lines of output
       are displayed.

Display Operation Modes

/Overwrite specifies that the debugger's output can overwrite program
       output.  In this mode, the application and the debugger are
       forced to share the same display area.

       This option may be used to conserve the amount of memory required
       to run VIDEO.  This option should not be used if you wish to
       debug a screen-oriented application (e.g., a graphics
       application) on the same machine.  See the section entitled
       "Debugging Graphics Applications".

/Page  specifies that page 0 of screen memory is to be used for the
       application's screen and that page 1 of screen memory should be
       used for the debugger's screen.  This option may be selected when
       using a graphics adapter such as the CGA, EGA or VGA.  Use of the
       Page option results in faster switching between the application
       and debugger screens and makes use of the extra screen memory
       available with the adapter.

       This option should not be used if you wish to debug a graphics
       application on the same machine.  See the section entitled
       "Debugging Graphics Applications".

/Swap  specifies that the application's screen memory and the debugger's
       screen memory are to be swapped back and forth using a single
       page.  The debugger allocates an area in its own data space for
       the inactive screen.  This reduces the amount of memory available
       to the application.  It also takes more time to switch between
       the application and debugger screens.

       This option MUST be used when debugging a graphics application on
       the same machine and a second monitor is not available.  See the
       section entitled "Debugging Graphics Applications".

/Two   specifies that a second monitor is connected to the system.  If
       the monitor type (Monochrome, Color, Colour, Ega43, Vga50) is not
       specified then the monitor that is not currently being used is
       selected for the debugger's screen.  If the monitor type is
       specified then the monitor corresponding to that type is used for
       the debugger's screen.

       This option should be used when debugging a graphics application
       on the same machine and a second monitor is available.  See the
       section entitled "Debugging Graphics Applications".

The default display operation is as follows:

   1. If you have a two display system, VIDEO uses both displays with
      the program output appearing on the active monitor and the
      debugger output appearing on the alternate monitor.  In other
      words, the Two option is selected by default.
   2. If you have one of the CGA, EGA or VGA graphics adapters installed
      in your system then VIDEO will select the Page option by default.
   3. Under all other circumstances, VIDEO will select the Swap option
      by default.

/Checksize=space specifies the minimum amount of storage, in kilobytes,
       that VIDEO is to provide to DOS for the purpose of running a
       program via the debugger's SYstem command (this command is
       described under the topic "SYSTEM").  This option is useful when
       the application that is being debugged uses up most or all of
       available storage, leaving insufficient memory to spawn secondary
       programs.  In order to provide the requested amount of free memory
       to DOS, the debugger will checkpoint as much of the application
       as is required.

       Checkpointing involves temporarily storing a portion of the
       memory-resident application on disk and then reusing the part of
       memory that it occupied for the spawned program.  When the
       spawned program terminates, the checkpointed part of the
       application is restored to memory.

       The default amount is 0K bytes.  In this case, the spawned
       program may or may not be run depending on how much free storage
       is available to DOS to run the program.

┌──────────────────────────────────────────────────────────────────────┐
│ WARNING!  If the application being debugged installs one or more     │
│ interrupt handlers, the use of this option could hang your system.   │
│ Your system could lock up if the debugger checkpoints a portion of   │
│ the application's code that contains an interrupt handler.           │
└──────────────────────────────────────────────────────────────────────┘

/Dynamic=space specifies the amount of dynamic storage that VIDEO is to
       reserve for items such as windows, user-defined symbols, etc.
       The default amount that is set aside is 20480 bytes (20
       Kilobytes).

/NOFpu requests that the debugger ignore the presence of a math
       coprocessor.  No memory will be allocated by the debugger for
       saving the context of the 80x87 numeric data processor.  Use this
       option if your application will not use the math coprocessor and
       you wish to reduce the amount of memory required by the debugger.

/Invoke=file_spec may be used to specify an alternate name for the
       debugger command file which is to be automatically invoked at
       start-up time.  The default file name is "PROFILE.DBG".  VIDEO
       command files are found in the current directory or one of the
       directories listed in the DOS PATH environment string.

/NOInvoke specifies that the default debugger command file is not to be
       invoked.

/NOMouse requests that the debugger ignore any attached mouse.  This may
       be necessary if the program being debugged also uses the mouse
       and the mouse driver installed on the system does not support two
       applications sharing the mouse at the same time.  The program
       "CHKMOUSE.COM" will inform you if the mouse driver supports this
       function.  To determine the capabilities of your mouse driver,
       run the CHKMOUSE program at the DOS command prompt.

       Example:
          C>chkmouse

       The program displays a single line telling you that either your
       mouse driver supports applications sharing the mouse, that it
       does not support applications sharing the mouse, or that there is
       no mouse driver installed.  This program is provided with VIDEO.

       In order to use a mouse, you must install the IBM Mouse Driver
       program that is supplied with the IBM Mouse.  Alternatively, you
       may use a mouse and mouse driver that are compatible with the IBM
       Mouse and IBM Mouse Driver.  The IBM Mouse Driver is installed by
       running the "MOUSE.COM" program.

       Example:
          C>\dos\mouse

/Registers=number may be used to specify how many register sets to set
       aside for the recording of register contents.  The default number
       of register sets is 2.  See the description of the Register
       command for more information (this command is described under the
       "REGISTER" topic).

/REMotefiles may be used in conjunction with the remote debugging
       capabilities of the debugger.  Remote debugging involves using
       two personal computers.  One, called the "task machine", is used
       to run the application; the other, called the "debugger machine",
       is used to run the debugger.  When REMotefiles is specified, all
       debugger files (except "trap" files) and application source files
       are opened on the task machine rather than the debugger machine
       (if you are doing local debugging, these two machines are
       actually the same).  The "trap" file must be located on the
       debugger machine because it contains the code to open files on
       the task machine.

       Note that the PATH environment variable on the task machine is
       always used in locating executable image files.  When REMotefiles
       is specified, the debugger also uses the task machine's PATH
       environment variable to locate debugger command files.

/REServesym=space specifies the amount of space that VIDEO is to reserve
       for symbolic information obtained through the NEW /SYmbol
       command.  The default amount that is set aside is 0 bytes.

/NOSNow requests that VIDEO omit the vertical retrace delay on CGA
       adapters when writing to video memory directly.  The omission of
       this delay will speed up display output.

/NOSymbols requests that VIDEO omit all debugging information when
       loading an executable image.  Information regarding global and
       local symbol names, data types, and line numbers is not
       processed.

/TRap=trap_file[;trap_parm] may be specified when debugging an
       application on a remote machine or debugging an application
       running under a 32-bit DOS extender.  It may also be used to disable
       the use of 386/486 Debug Registers.  You must specify the name of
       one of the "trap" files provided with VIDEO.  Under DOS, the file
       extension defaults to ".TRP".  The "BIN" directory contains the
       trap files provided with VIDEO.

       Under DOS, if you do not specify a trap file, the default trap
       file "STD.TRP" will be loaded.  This interface module supports
       debugging on the local computer system running DOS.  No remote
       debugging is possible.
::::ERROR
┌──────────────────────────────────────────────────────────────────────┐
│ ERror  text_string | "{" text_string "}"                             │
└──────────────────────────────────────────────────────────────────────┘

The Error command may be used to display an error message on the screen
which requires an acknowledgement.  This command can be used most
effectively in VIDEO command files.  Currently executing command files
are terminated when the ERror command is issued.

Example:
   DBG>if ~ dbg$fpu {error No 80x87 processor/emulator!}

The message text is displayed in an Error window.
::::EXAMINE
┌──────────────────────────────────────────────────────────────────────┐
│ Examine                                                              │
│     [/Byte]         exam_data                                        │
│     /Word           exam_data                                        │
│     /Dword          exam_data                                        │
│     /Pointer        exam_data                                        │
│     /Assembly       addr_data                                        │
│     /Source         addr_data                                        │
│     /IOByte         port_data                                        │
│     /IOWord         port_data                                        │
│     /IODword        port_data                                        │
└──────────────────────────────────────────────────────────────────────┘

The Examine command is used to display the contents of memory and I/O
ports in one of several different ways.


Examining Memory as Data
────────────────────────
/Byte exam_data When this qualifier is used, the output from the Examine
       command is written to the Dialogue window.  The output is
       formatted into 8-bit values (bytes) using hexadecimal (base 16)
       notation.  The default qualifier is /Byte.

/Word exam_data When this qualifier is used, the output from the Examine
       command is written to the Dialogue window.  The output is
       formatted into 16-bit values (words) using hexadecimal (base 16)
       notation.  The most significant byte of each word is shown first.

/Dword exam_data When this qualifier is used, the output from the
       Examine command is written to the Dialogue window.  The output is
       formatted into 32-bit values (doublewords) using hexadecimal
       (base 16) notation.  The most significant byte of each doubleword
       is shown first.

/Pointer exam_data When this qualifier is used, the output from the
       Examine command is written to the Dialogue window.  The output is
       formatted into segment/offset pairs (segment:offset) using
       hexadecimal (base 16) notation.

   exam_data ::= [start_addr_expr]
                       [ "," [next_addr_expr]
                       [ "," [len_expr]
                       [ "," rpt_expr ] ] ]

The starting address start_addr_expr is any expression that defines a
segment and offset of memory to be displayed.  The next address
next_addr_expr is any expression that defines the next segment and
offset of memory to be displayed.  The length value len_expr is any
expression that defines the amount of memory to be displayed.  The
repetition count rpt_expr may be any expression that defines the number
of times the command is to be repeated.

Example:
   DBG>examine ds:0x0000
   DBG>examine ds:0x0000,.+0x10,0x10

The above two examples are equivalent.  Memory is displayed as a
sequence of bytes starting at the segment defined by the contents of the
DS register and an offset of 0.

The default next_addr_expr is defined as the current starting address
(".") plus 16 (decimal).  The default len_expr is 16 (decimal).

One of the features of the Examine command is its ability to follow
linked lists.  This can be illustrated with an example from the C
programming language.  Imagine that the following structure was defined.

   typedef struct list_entry
     {
       int               entry_number;
       struct list_entry *next;
       int               flags;
       char              *buff_addr;
     } LIST;

   extern LIST *listhead;  /* start of linked list */

The structure definition indicates that the second item in each entry
points to the next entry in the linked list.  To examine the entries in
the linked list (in 16-bit mode), the following command could be issued.

Example:
   DBG>ex/word *listhead,*(.+2),list_entry
   2134:0100 0001 013C 0774 8B55
   2134:013C 0002 011E 0770 8B97
   2134:011E 0003 0142 0074 8B34
   2134:0142 0004 0000 0070 8B55

We use the pointer operator * to indicate memory indirection.  After the
first line is displayed, the current memory location "." is defined to
be "2134:0100".  Hence, ".+2" is "2134:0102" and "*(2134:0102)" is
"013C".  Therefore, the next memory location to be displayed is
2134:013C.  Each time the space bar is pressed, the next memory location
is displayed and the value for "." is updated.

   1. In the above example, we are using type information when we refer
      to list_entry.  In order to specify a type name such as this, the
      "d2" compiler option must have been specified when the module was
      compiled.
   2. In addition, the "debug types" or "debug all" linker option must
      have preceded the name of the object file containing the module
      when the application was linked.


Examining Memory as Instructions
────────────────────────────────
/Assembly addr_data When this qualifier is used, the output from the
       Examine command is written to the Assembly window if one is
       present on the screen; otherwise output is written to the
       Dialogue window.  The output is formatted into Intel machine
       language instructions.  Numeric values are displayed in
       hexadecimal (base 16) notation.  For any locations that are
       displayed as "<symbol_name>+offset", the value for "offset" is
       displayed in the current numeric radix.

/Source addr_data When this qualifier is used, the output from the
       Examine command is written to the Source window if one is present
       on the screen; otherwise output is written to the Dialogue
       window.  If both line number information and the source file are
       available then the source lines are displayed.  If only line
       number information is available then only line numbers are
       displayed.  If no information is available then no lines will be
       displayed in the Source window.

       If present, line number information is extracted from the
       executable image file.  Source lines are extracted from a source
       file provided that the file can be located.  For more
       information, see the description of the Set Source command.

   addr_data ::= [start_addr_expr] [ "," rpt_expr ]

The starting address start_addr_expr is any expression that defines a
segment and offset of memory to be displayed in the form of assembly
instructions and source lines.  The repetition count rpt_expr may be any
expression that defines the number of times the command is to be
repeated.  A positive repetition count is equivalent to that many
presses of the space bar (next).  A negative repetition count is
equivalent to that many presses of the "P" key (previous).

Example:
   DBG>examine/source main_
   DBG>e/s main_

In the above example, two equivalent commands are shown.  The latter is
simply the short form for the former command.  Source lines
corresponding to the application entry point main_ are displayed.

A starting address may also be specified in terms of the module name and
line number.

Example:
   DBG>ex/source calendar@36

The module name need not be specified when it is the current module
under examination.

Example:
   DBG>ex/source @159

Line numbers are shown in the Source window.  Source line information
must be available in order to show source line numbers.

   1. Either compiler options "d1" or "d2" must have been specified when
      the module was compiled.
   2. The "debug lines" or "debug all" linker option must have preceded
      the name of the object file containing the module when the
      application was linked.


Examining Input/Output Ports
────────────────────────────
/IOByte port_data When this qualifier is used, the specified port is
       read and output from the Examine command is written to the
       Dialogue window.  The output is formatted into an 8-bit value
       (byte) using hexadecimal (base 16) notation.

/IOWord port_data When this qualifier is used, the specified port is
       read and output from the Examine command is written to the
       Dialogue window.  The output is formatted into 16-bit values
       (words) using hexadecimal (base 16) notation.  The most
       significant byte of each word is shown first.

/IODword port_data The IODword qualifier is supported on 386 systems or
       higher.  When this qualifier is used, the specified port is read
       and output from the Examine command is written to the Dialogue
       window.  The output is formatted into 32-bit values (doublewords)
       using hexadecimal (base 16) notation.  The most significant byte
       of each doubleword is shown first.

   port_data ::= [start_addr_expr] [ "," rpt_expr ]

The starting address start_addr_expr is any expression that defines an
input/output port at which to begin reading data.  The repetition count
rpt_expr may be any expression that defines the number of times the
command is to be repeated.  A positive repetition count is equivalent to
that many presses of the space bar (next).
::::F77_OPERATORS
VIDEO supports most FORTRAN 77 operators and includes an additional set
of operators for convenience.  The additional operators are patterned
after those available in the C programming language.

The grammar that VIDEO supports is close to that of the FORTRAN 77
language but there are a few instances where space characters must be
used to clear up any ambiguities.  For example, the expression

   1.eq.x

will result in an error since VIDEO will form a floating-point constant
from the "1." leaving the string "eq.x".  If we introduce a space
character after the "1" then we clear up the ambiguity.

   1 .eq.x

Unlike FORTRAN, the parser in VIDEO treats spaces as significant
characters.  Thus spaces must not be introduced in the middle of symbol
names, constants, multi-character operators like .EQ.  or //, etc.

Operators are presented in order of precedence, from lowest to highest.
Operators on the same line have the same priority.

                                           Lowest Priority
   Assignment Operators
       =  +=  -=  *=  /=  %=  &=  |=  ^=  <<=  >>=
   Logical Operators
       .EQV.  .NEQV.
       .OR.
       .AND.
       .NOT.
   Bit Operators
       |
       ^
       &
   Relational Operators
       .EQ.  .NE.  .LT.  .LE.  .GT.  .GE.
   Shift and Concatenation Operators
       <<  >>  //
   Arithmetic Operators
       +  -
       *  /  %
       ** (unsupported)
   Unary Operators
       +  -
       ~  ++  --  &   *   %
       [type_name] unary_expr
       ?
   Binary Address Operator
       :
                                           Highest Priority

Parentheses can be used to order the evaluation of an expression.

In addition to the operators listed above, a number of primary
expression operators are supported.  These operators are used in
identifying the object to be operated upon.

()     subscripting, substringing, or function call

.      field selection

->     field selection using a pointer

The following built-in functions may be used to convert the specified
argument to a particular type.

   INT( )      conversion to integer
   REAL( )     conversion to real
   DBLE( )     conversion to double-precision
   CMPLX( )    conversion to complex
   DCMPLX( )   conversion to double-precision complex

The following sections describe the operators presented above.


Assignment Operators for the FORTRAN Grammar
────────────────────────────────────────────

=      Assignment:  The value on the right is assigned to the object on
       the left.

+=     Additive assignment:  The object on the left is augmented by the
       value on the right.

-=     Subtractive assignment:  The object on the left is reduced by the
       value on the right.

*=     Multiplicative assignment:  The object on the left is multiplied
       by the value on the right.

/=     Division assignment:  The object on the left is divided by the
       value on the right.

%=     Modulus assignment:  The object on the left is updated with
       MOD(left,right).  The result is the remainder when the value of
       the object on the left is divided by the value on the right.

&=     Bit-wise AND:  The bits in the object on the left are ANDed with
       the bits of the value on the right.

|=     Bit-wise inclusive OR:  The bits in the object on the left are
       ORed with the bits of the value on the right.

^=     Bit-wise exclusive OR:  The bits in the object on the left are
       exclusively ORed with the bits of the value on the right.

<<=    Left shift:  The bits in the object on the left are shifted to
       the left by the amount of the value on the right.

>>=    Right shift:  The bits in the object on the left are shifted to
       the right by the amount of the value on the right.  If the object
       on the left is described as unsigned, the vacated high-order bits
       are zeroed.  If the object on the left is described as signed,
       the sign bit is propagated through the vacated high-order bits.
       VIDEO treats registers as unsigned items.


Logical Operators for the FORTRAN Grammar
─────────────────────────────────────────

.EQV.  Logical equivalence:  The logical equivalence of the value on the
       left and the value on the right is produced.

.NEQV. Logical non-equivalence:  The logical non-equivalence of the
       value on the left and the value on the right is produced.

.OR.   Logical inclusive disjunction:  The logical OR of the value on
       the left and the value on the right is produced.

.AND.  Logical conjunction:  The logical AND of the value on the left
       and the value on the right is produced.

.NOT.  Logical negation:  The logical complement of the value on the
       right is produced.


Bit Operators for the FORTRAN Grammar
─────────────────────────────────────

|      Bit-wise OR:  The bits of the value on the left and the value on
       the right are ORed.

^      Bit-wise exclusive OR:  The bits of the value on the left and the
       value on the right are exclusively ORed.

&      Bit-wise AND:  The bits of the value on the left and the value on
       the right are ANDed.


Relational Operators for the FORTRAN Grammar
────────────────────────────────────────────

.EQ.   Equal:  If the value on the left is equal to the value on the
       right then the result is 1; otherwise the result is 0.

.NE.   Not equal:  If the value on the left is not equal to the value on
       the right then the result is 1; otherwise the result is 0.

.LT.   Less than:  If the value on the left is less than the value on
       the right then the result is 1; otherwise the result is 0.

.LE.   Less than or equal:  If the value on the left is less than or
       equal to the value on the right then the result is 1; otherwise
       the result is 0.

.GT.   Greater than:  If the value on the left is greater than the value
       on the right then the result is 1; otherwise the result is 0.

.GE.   Greater than or equal:  If the value on the left is greater than
       or equal to the value on the right then the result is 1;
       otherwise the result is 0.


Arithmetic/Logical Shift Operators for the FORTRAN Grammar
──────────────────────────────────────────────────────────

<<     Left shift:  The bits of the value on the left are shifted to the
       left by the amount described by the value on the right.

>>     Right shift:  The bits of the value on the left are shifted to
       the right by the amount described by the value on the right.  If
       the object on the left is described as unsigned, the vacated
       high-order bits are zeroed.  If the object on the left is
       described as signed, the sign bit is propagated through the
       vacated high-order bits.  VIDEO treats registers as unsigned
       items.


Concatenation Operator for the FORTRAN Grammar
──────────────────────────────────────────────

//     String concatenation:  The concatenation of the character string
       value on the left and right is formed.


Binary Arithmetic Operators for the FORTRAN Grammar
───────────────────────────────────────────────────

+      Addition:  The value on the right is added to the value on the
       left.

_      Subtraction:  The value on the right is subtracted from the value
       on the left.

*      Multiplication:  The value on the left is multiplied by the value
       on the right.

/      Division:  The value on the left is divided by the value on the
       right.

%      Modulus:  The modulus of the value on the left with respect to
       the value on the right is produced.  The result is the remainder
       when the value on the left is divided by the value on the right.

**     Exponentiation:  This operation is not supported by VIDEO.

Unary Arithmetic Operators for the FORTRAN Grammar
──────────────────────────────────────────────────

+      Plus:  The result is the value on the right.

_      Minus:  The result is the negation of the value on the right.

~      Bit-wise complement:  The result is the bit-wise complement of
       the value on the right.

++     Increment:  Both prefix and postfix operators are supported.  If
       the object is on the right, it is pre-incremented by 1 (e.g.,
       ++x).  If the object is on the left, it is post-incremented by 1
       (e.g., x++).

_ _    Decrement:  Both prefix and postfix operators are supported.  If
       the object is on the right, it is pre-decremented by 1 (e.g.,
       --x).  If the object is on the left, it is post-decremented by 1
       (e.g., x--).

&      Address of:  The result is the address (segment:offset) of the
       object on the right (e.g., &main).

*      Points:  The result is the value stored at the location addressed
       by the value on the right (e.g., *(ds:100), *string.loc).  In the
       absence of typing information, the value on the right is treated
       as a pointer into the stack segment and a near pointer is
       produced.

                (SS:00FE) = FFFF
          var:  (SS:0100) = 0152
                (SS:0102) = 1240
                (SS:0104) = EEEE

       In the following example, memory locations are displayed starting
       at DS:152 for 16-bit mode and at DS:12400152 for 32-bit mode.

       Example:
          DBG>examine/byte *100

%      Value at address:  The result is the value stored at the location
       addressed by the value on the right (e.g., %(ds:100),
       %string.loc).  In the absence of typing information, the value on
       the right is treated as a pointer into the stack segment and a
       far pointer is produced.

                (SS:00FE) = FFFF
          var:  (SS:0100) = 0152
                (SS:0102) = 1240
                (SS:0104) = EEEE

       In the following example, memory locations are displayed starting
       at 1240:0152 for 16-bit mode and at EEEE:12400152 for 32-bit
       mode.

       Example:
          DBG>examine/byte %100

       Note that this operator is not found in the FORTRAN 77
       programming language.


Special Unary Operators for the FORTRAN Grammar
───────────────────────────────────────────────

?      Existence test:  The "?" unary operator may be used to test for
       the existence of a symbol.

       Example:
          DBG>print ?id

       The result of this expression is 1 if "id" is a symbol known to
       VIDEO and 0 otherwise.  If the symbol does not exist in the
       current scope then it must be qualified with its module name.
       Automatic symbols exist only in the current subprogram.


Binary Address Operator for the FORTRAN Grammar
───────────────────────────────────────────────

:      Memory locations can be referenced by using the binary ":"
       operator and a combination of constants, register names, and
       symbol names.  In the Intel 80x86 architecture, a memory
       reference requires a segment and offset specification.  A memory
       reference using the ":" operator takes the following form:

          segment:offset

       The elements segment and offset can be expressions.

       Example:
          (ES):(DI+100)
          (SS):(SP-20)


Primary Expression Operators for the FORTRAN Grammar
────────────────────────────────────────────────────

()     Elements of an array can be identified using subscript
       expressions.

.      The "." operator indicates field selection in a structure.  This
       operator is useful in mixed language applications where part of
       the application is written in the C programming language.  In the
       following example, tyme2 is a structure and tm_year is a field in
       the structure.

       Example:
          DBG>print tyme2.tm_year

->     The "->" operator indicates field selection when using a pointer
       to a structure.  This operator is useful in mixed language
       applications where part of the application is written in the C
       programming language.  In the following example, tyme is the
       pointer and tm_year is a field in the structure to which it
       points.

       Example:
          DBG>print tyme->tm_year
::::FLIP
┌──────────────────────────────────────────────────────────────────────┐
│ Flip  [ ON | OFf ]                                                   │
└──────────────────────────────────────────────────────────────────────┘

The Flip command is used to display the application's screen.  Under
DOS, the "Page" or "Swap" options must have been specified when the
debugger was invoked.  To return to the VIDEO display screen, any key
may be pressed or the left mouse button may be clicked.  If neither of
these options were specified then this form of the command will have no
effect.

The "on" and "off" options are used to turn screen switching "on" or
"off".  By default, VIDEO will switch between the application's screen
and the debugger's screen (flip on) unless the remote debugging feature
is used.  To prevent VIDEO from switching between screens, flipping may
be turned "off".
::::GO
┌──────────────────────────────────────────────────────────────────────┐
│ Go         [ start_addr_expr "," ] [ tmp_brk_addr_expr ]             │
│ Go [/Keep] [ start_addr_expr "," ]                                   │
└──────────────────────────────────────────────────────────────────────┘

The Go command is used to start or continue program execution.
Execution resumes at the specified starting address start_addr_expr or,
in the absence of one, the location defined by the current contents of
the CS:IP or CS:EIP register pair.

If a starting address is specified, it must be followed by a comma.  In
the following example, VIDEO is instructed to resume execution at the
start of "rtn1".

Example:
   DBG>go rtn1,

The following example instructs VIDEO to resume execution at the start
of "rtn1" and also sets a temporary break point at "rtn1+73" so that
execution is suspended before executing the instruction at "rtn1+73".

Example:
   DBG>go rtn1,rtn1+73

A temporary break point may be specified without a starting address.  A
temporary break point is similar to a normal break point except that
only one of them is permitted.  Every time you issue a new Go command,
the previous temporary break point (if it exists) is discarded unless
the /Keep sub-command is specified.  If you wish to retain the previous
temporary break point then you may not specify a new one (since you can
have only one).

Example:
   DBG>go rtn1
   DBG>go rtn2

In the above example, the temporary break point at "rtn1" is replaced by
the temporary break point at "rtn2" when the second Go command is
issued.

Example:
   DBG>go rtn1
   DBG>go

In the above example, the temporary break point at "rtn1" is removed
when the second Go command is issued.

Example:
   DBG>go rtn1
   DBG>go/keep

In the above example, the temporary break point at "rtn1" is kept when
the second Go command is issued.

See the description of the Break command for more information on break
points.
::::HELP
┌──────────────────────────────────────────────────────────────────────┐
│ Help   [topic]                                                       │
└──────────────────────────────────────────────────────────────────────┘

The Help command may be used to obtain help on a particular topic.  If
no topic is specified then a default topic is displayed.  The default
topic includes a list of topics for which help is available.

Unique short forms may be specified for the desired topic.

Example:
   DBG>help go

The above example requests help on the VIDEO Go command.

Help information is displayed in the View window.  Manipulation of this
window with keys and mouse is described under the topics "KEYS" and
"MOUSE".
::::IF
┌──────────────────────────────────────────────────────────────────────┐
│ IF  expr  if_cmd_list  [ else_cmd_list ]                             │
└──────────────────────────────────────────────────────────────────────┘

The specified expression expr is evaluated and if it results in a
non-zero value then the list of debugger commands contained in
if_cmd_list is executed; otherwise the list of commands contained in
else_cmd_list is executed.  The two command lists are separated from one
another by the use of curly braces ({}).

Example:
   DBG>break/set gorun { if x>100 {print{done}}{go/keep} }

In the above example, a break point will occur each time the "gorun"
routine is entered.  The IF command is evaluated by the debugger and if
the result is "true" (i.e., not zero) then the message "done" will be
printed in the Dialogue window and the debugger will prompt for another
command; otherwise execution is resumed (keeping any temporary break
point that we may have specified).

A command of the sort presented next is very useful in locating a
problem in an application.  Let us assume that we are trying to discover
which routine calls our "gorun" routine such that the variable "x" has a
zero value after the "gorun" routine has executed.  The example assumes
a 16-bit application.

Example:
   DBG>br gorun {br %sp {if x==0 {} {br/cl /.;go/k}}; go/k}

In the above example, the commands

   br %sp {if x==0 {} {br/cl /.;go/k}}
   go/k

are executed each time the "gorun" routine is entered.  This first
command defines a break point at the return address of the calling
routine.  We are assuming that "gorun" was invoked by a "far" call;
hence the stack top contains a 32-bit segment:offset return address in
our 16-bit example.  The second command resumes execution of the
application.  The command

   if x==0 {} {br/cl /.;go/k}

is executed each time a return is made to the calling routine.  If the
value of "x" is zero then no commands are executed and the debugger is
entered (this may be the error case for which we are searching).
Otherwise the break point for this location is cleared and execution is
resumed (keeping any temporary break point that we may have specified).
::::INVOKE
┌──────────────────────────────────────────────────────────────────────┐
│ INvoke  cmd_file { parm | "{" parm "}" }                             │
│ <                                                                    │
└──────────────────────────────────────────────────────────────────────┘

The INvoke or < command is used to invoke a file containing a number of
VIDEO commands.  The file specification cmd_file has an operating system
dependent form.  For DOS and OS/2, the format is:

   [d:][path]filename[.ext]

For QNX, the format is:

   [//node][path]filename[.ext]

If no file suffix or extension is specified (i.e., both the period and
extension are omitted) then the default is ".dbg".

Under DOS or OS/2, the search order for command files is as follows:

   1. If only filename or filename.ext are specified, VIDEO will first
      attempt to locate the file in the current working directory.
   2. It will then search the paths listed in the PATH environment
      variable.  You should ensure that the "BINB" directory of the
      WATCOM compiler package is included in the PATH environment
      variable.  This directory contains the command files provided with
      VIDEO.

Under QNX, the search order for command files is as follows:

   1. If only filename or filename.ext are specified, VIDEO will first
      attempt to locate the file in the current working directory.
   2. the paths listed in the WVIDEO_PATH environment variable,
   3. the path listed in the HOME environment variable, and, finally,
   4. the "/etc/wvideo" directory.  The command files provided with
      VIDEO are usually located in the "/etc/wvideo" directory.

Parameters may be passed to the command file.  If any of the parameters
require the use of a semicolon (";") or a space then you should use "{"
and "}" since the semicolon is interpreted as a command separator and
the space is interpreted as a parameter separator by VIDEO.

The parameters are matched up with sequences of <#> in the command file,
where # is a number from 1 to 9.  The first parameter is substituted for
every occurrence of <1>, the second for every occurrence of <2>, and so
on.  Any occurrences of <0> are replaced by a unique integer value which
is supplied by the debugger each time the file is invoked.  This feature
permits the creation of unique variables with each invocation of the
command file.

A number of command files are provided with VIDEO that provide excellent
examples of the power and flexibility of command files.

In the following example, assume that the file "count.dbg" contains the
following two lines:

   /cnt_<1>=0
   break/set <1> {/cnt_<1>++; go/keep}

If you enter one of the commands:

   invoke count printf
   <count printf

then each appearance of "<1>" is replaced by "printf" and the resultant
commands are executed.

Example:
   DBG>/cnt_printf=0
   DBG>break/set printf {/cnt_printf++; go/keep}

Each time the "printf" routine is entered, the debugger will increment
the user-defined variable cnt_printf and resume execution (keeping any
temporary break point that we may have specified).  When execution of
the application terminates, the current value of cnt_printf may be
examined by using the Print command to determine how many times the
"printf" routine was executed.

Example:
   set pf <1> {
       if !?_dbg@pf_<1> {/_dbg@pf_<1>=0};
       if (++_dbg@pf_<1>)&1 {<2>} {<3>}
   }

In the above example, taken from "toggle.dbg", three parameters are
specified to the command file.

As shown in the previous example, one VIDEO command line may be split
across several lines of a command file.  A line can be split at an
opening brace ("{").  To construct the command line, VIDEO will continue
to read in input lines until the matching closing brace is found ("}").

For additional information on command files, see also the description of
the Set Implicit command.
::::KEYS
Window Manipulation with Keys
─────────────────────────────

The window which contains the text cursor is called the "active" window.
The active window is the window that will respond to keystrokes.  In
general, keys such as the Cursor Up and Down keys perform similar
functions in all windows.  The following keys perform identical
functions in all windows.

Ctrl/Enter may be used to engage a text selection process which will be
       concluded by the appearance of the Action window.  When text
       selection is engaged, a block cursor will appear on the screen.
       The cursor keys may be used to stretch the block cursor to the
       left, right, up and down, thereby highlighting a portion of the
       text visible on the screen.  The Ctrl/Cursor Left and Ctrl/Cursor
       Right keys extend the block cursor to the left or right by a
       token at a time.  A second press of the Ctrl/Enter key causes the
       Action window to pop up on the screen.

When the "Show source" entry is selected, the source/assembly code
corresponding to the selected text is displayed in the Source and
Assembly windows (if present on the screen).

A line appears in the Dialogue window that indicates the address of the
previous source/assembly code and the new source/assembly code under
examination.

Example:
   0x65CB:0x0012 => ClearScreen

You can use this entry to return to the previous location by moving the
text cursor to the Dialogue window using the Tab keys and highlighting
the address that is displayed on the left of the "=>" using the
Ctrl/Enter and cursor keys.  In the above example, this would be the
entry "0x65CB:0x0012" (the segment and offset of the previous location
under examination).

The following keys perform identical functions in all windows except the
View and Error windows.

Tab    may be used to move the text cursor to the next window on the
       screen.

Shift/Tab (Backtab) may be used to move the text cursor to the previous
       window on the screen.

Escape may be used to move directly to the Prompt window.

Ctrl/D may be used to shift the entire active window down on the screen.

Ctrl/U combination may be used to shift the entire active window up on
       the screen.

Ctrl/P may be used to invoke the Paint menu for the active window.

The following keys perform identical functions in all windows except the
Prompt, View and Error windows.

Ctrl/L may be used to move the active window to the left.

Ctrl/R may be used to move the active window to the right.

Ctrl/G may be used to grow the size of the active window.

Ctrl/S may be used to shrink the size of the active window.

Ctrl/N may be used to narrow the size of the active window.

Ctrl/W may be used to widen the size of the active window.

Ctrl/E may be used to erase the active window from the display.

Ctrl/Z may be used to zoom the active window between its normal size and
       the size of the entire screen.

The following sections describe in detail the responses to various keys
when a particular window is active.


Manipulating the Assembly Window with Keys
──────────────────────────────────────────

When the text cursor is positioned in the Assembly window, the Cursor
Left/Right, Cursor Up/Down, Page Up/Down, Home, End, and Enter keys may
be used to move about.

Cursor Left/Right
       may be used to scroll the text in the window left or right when
       the cursor moves to the left or right edge of the window.

Ctrl/Cursor Left/Right
       may be used to scroll the text in the window left or right
       without moving the cursor.

Cursor Up/Down
       may be used to scroll up and down through assembly instructions.

Page Up/Down
       may be used to scroll up and down through assembly instructions
       in increments of the number of lines in the window minus two.

Home   may be used to move to the beginning of the current compilation
       unit.

End    may be used to move to the end of the current module (compilation
       unit).

Enter  may be used to move directly to the assembly instruction
       referenced by the CS:IP (16-bit mode) or CS:EIP (32-bit mode)
       register pair.


Manipulating the Command Window with Keys
─────────────────────────────────────────

When the text cursor is positioned in the Command window, the Enter key
may be used to refresh the window.


Manipulating the Dialogue Window with Keys
──────────────────────────────────────────

When the text cursor is positioned in the Dialogue window, the Cursor
Up/Down, Page Up/Down, Home, End, and Enter keys may be used to move
about.

Cursor Left/Right
       may be used to scroll the text in the window left or right when
       the cursor moves to the left or right edge of the window.

Ctrl/Cursor Left/Right
       may be used to scroll the text in the window left or right
       without moving the cursor.

Cursor Up/Down
       may be used to scroll up and down through Dialogue window output,
       one line at a time.

Page Up/Down
       may be used to scroll up and down through Dialogue window output
       in increments of the number of lines in the window minus two.

Home   may be used to move to the beginning of Dialogue window output.

End    may be used to move to the end of Dialogue window output.

Enter  may be used to move to the end of Dialogue window output.

When the text cursor is positioned in the Prompt window, the Page Up,
Page Down, Ctrl/Page Up and Ctrl/Page Down keys may be used to scroll
the Dialogue window.

Page Up/Down
       may be used to scroll up and down through Dialogue window output,
       one line at a time.

Ctrl/Page Up and Ctrl/Page Down
       may be used to scroll up and down through Dialogue window output
       in increments of the number of lines in the window minus two.


Manipulating the FPU Window with Keys
─────────────────────────────────────

When the text cursor is positioned in the FPU window, the cursor and
Enter keys may be used to position to register (ST(0), ST(1), etc.) or
flag displays and modify register or flag contents.  The Home, End, Page
Up, and Page Down keys may be used to display register sets.  See the
description of the Register command for more information on register
sets.

Cursor Up, Down, Left and Right
       keys may be used to move the text cursor to register/flag content
       displays.

Enter  may used to modify register contents.  If the text cursor is
       positioned on a register when the Enter key is pressed, a
       register modification window is displayed on the screen and a new
       value may be entered.  The register may be left unmodified by
       just pressing the Enter key in response to the prompt for a new
       value.

       If the text cursor is positioned on a flag when the Enter key is
       pressed then its value is complemented.

Home   may be used to move to the oldest register set.

End    may be used to move to the most recent register set.

Page Up
       may be used to move backwards through register sets to the oldest
       register set.

Page Down
       may be used to move forwards through register sets to the most
       recent register set.

Insert
       may be used to switch between binary and decimal display formats.


Manipulating the Memory Window with Keys
────────────────────────────────────────

When the text cursor is positioned in the Memory window, the cursor,
Home, Page Up, Page Down and Enter keys may be used to position to
memory entries and modify their contents.

Cursor Up, Down, Left and Right
       may be used to move the text cursor to individual memory
       locations.

Insert
       may be used to modify the way in which memory locations are
       displayed.  Each subsequent press of the Insert key cycles the
       display through 8-bit bytes, 16-bit words, and 32-bit
       doublewords.  When 8-bit bytes are displayed, their ASCII
       equivalents are also displayed on the right-hand side of the
       window.

Delete
       may be used to select a new memory location to be displayed.  A
       prompt window appears for the new memory location.

Home   may be used to move directly to the original location of memory
       that was requested to be displayed.

Page Up/Down
       may be used to scroll up and down through the memory window in
       increments of the number of lines in the window minus two.

Enter  may used to modify the contents of the memory location upon which
       the text cursor is positioned.  When pressed, a memory
       modification window is displayed on the screen and a new value
       may be entered.  The entry may be left unmodified by just
       pressing the Enter key in response to the prompt for a new value.
       Bytes, words or doublewords may be entered, depending on the way
       in which memory is being displayed.


Manipulating the Prompt Window with Keys
────────────────────────────────────────

VIDEO commands are entered at the "DBG>" input prompt.

   DBG>

In multiple execution thread applications, the "DBG>" prompt is replaced
by a prompt that indicates the current thread.  The form of the prompt
is "ddd>" where "ddd" is the thread identification number.

Example:
   002>

When the text cursor is positioned in the Prompt window, the cursor,
Home, End, Ins, Del, Backspace and Enter keys may be used to recall,
edit and submit commands.

Cursor Up/Down
       may be used to scroll through previously entered commands.

Cursor Left/Right
       may be used to move the cursor left or right through a command
       line to make changes.

Ctrl/Cursor Left and Right
       keys may be used to move the cursor left or right one word at a
       time.

Home   may be used to move to the beginning of the command line.

End    may be used to move to the end of the command line.

Insert
       key may be used to flip between character insertion and
       overtyping modes.

Delete
       may be used to remove the character under the cursor.

Backspace
       (or Rubout) may be used to erase the character to the left of the
       cursor.

Enter  may be used to submit the command.

Command lines that exceed the screen width may be entered.  The command
line will scroll left or right depending on the cursor placement and
direction.

When the text cursor is positioned in the Prompt window, the Page Up,
Page Down, Ctrl/Page Up and Ctrl/Page Down keys may be used to scroll
the Dialogue window (see the earlier section describing Dialogue window
manipulation).


Manipulating the Register Window with Keys
──────────────────────────────────────────

When the text cursor is positioned in the Register window, the cursor
and Enter keys may be used to position to register displays and modify
register contents.  The Home, End, Page Up, and Page Down keys may be
used to display register sets.  See the description of the Register
command for more information on register sets.

Cursor Up, Down, Left and Right
       may be used to move the text cursor to register/flag content
       displays.

Enter  may used to modify register contents.  If the text cursor is
       positioned on a register when the Enter key is pressed, a
       register modification window is displayed on the screen and a new
       value may be entered.  The register may be left unmodified by
       just pressing the Enter key in response to the prompt for a new
       value.

       If the text cursor is positioned on a flag when the Enter key is
       pressed then its value is complemented.

Home   may be used to move to the oldest register set.

End    may be used to move to the most recent register set.

Page Up
       may be used to move backwards through register sets to the oldest
       register set.

Page Down
       may be used to move forwards through register sets to the most
       recent register set.


Manipulating the Source Window with Keys
────────────────────────────────────────

When the text cursor is positioned in the Source window, the Cursor
Up/Down, Page Up/Down, Home, End, and Enter keys may be used to move
about.

Cursor Left/Right
       may be used to scroll the text in the window left or right when
       the cursor moves to the left or right edge of the window.

Ctrl/Cursor Left/Right
       may be used to scroll the text in the window left or right
       without moving the cursor.

Cursor Up/Down
       may be used to scroll up and down through source lines.

Page Up/Down
       may be used to scroll up and down through source lines in
       increments of the number of lines in the window minus two.

Home   may be used to move to the beginning of the current module
       (compilation unit).

End    may be used to move to the end of the current module (compilation
       unit).

Enter  may be used to move directly to the source line referenced by the
       CS:IP (16-bit mode) or CS:EIP (32-bit mode) register pair.

Manipulating the Stack Window with Keys
───────────────────────────────────────

When the text cursor is positioned in the Stack window, the cursor,
Home, End, Page Up, Page Down and Enter keys may be used to position to
stack entries and modify their contents.

Cursor Up, Down, Left and Right
       may be used to move the text cursor to individual stack entries.

Insert
       may be used to modify the way in which stack entries are
       displayed.  Each subsequent press of the Insert key cycles the
       display through 8-bit bytes, 16-bit words, and 32-bit
       doublewords.  When 8-bit bytes are displayed, their ASCII
       equivalents are also displayed on the right-hand side of the
       window.

Home   may be used to move directly to the stack entry referenced by
       SS:SP (16-bit mode) or SS:ESP (32-bit mode).

End    may be used to move directly to the stack entry referenced by
       SS:BP (16-bit mode) or SS:EBP (32-bit mode).

Page Up/Down
       may be used to scroll up and down through the stack in increments
       of the number of lines in the window minus two.

Enter  may used to modify the contents of the stack entry upon which the
       text cursor is positioned.  When pressed, a stack modification
       window is displayed on the screen and a new value may be entered.
       The entry may be left unmodified by just pressing the Enter key
       in response to the prompt for a new value.


Manipulating the Thread Window with Keys
────────────────────────────────────────

When the text cursor is positioned in the Thread window, the cursor,
Page Up, Page Down and Enter keys may be used to position to thread
entries and modify their contents.

Cursor Up, Down, Left and Right
       may be used to move the text cursor to thread fields.

Page Up/Down
       may be used to scroll up and down through the thread window in
       increments of the number of lines in the window minus two.

Enter  may be used to modify the contents of the thread field upon which
       the text cursor is positioned.  When pressed on an "id" field,
       the selected thread becomes the current thread.  The other
       windows on the screen will change to reflect the selection of
       another execution thread.

       When pressed on a "state" field, the selected thread's state is
       changed to either "frozen" or "runnable".


Manipulating the Variable Window with Keys
──────────────────────────────────────────

When the text cursor is positioned in the Variable window, the Cursor
Up/Down, Enter, Backspace and "S" keys may be used.

Cursor Up/Down
       may be used to move up and down through the fields of a
       structure.  Entries that represent structures are displayed by
       using "{...}".  Entries that represent arrays are displayed by
       using "(...)".

Page Up/Down
       may be used to scroll up and down through the Variable window in
       increments of the number of lines in the window.

Enter  can be used to display the contents of a field.

Backspace
       can be used to return to the previous level.

"S"    can be used to display an entry as a string.  The Backspace key
       can be used to return to the original display format.


Manipulating the View Window with Keys
──────────────────────────────────────

When the text cursor is positioned in the View window, the cursor, Page
Up/Down, Home, End, and Enter keys may be used to move about.  The /, ?,
', and " keys may be used to search for text.

Cursor Up/Down
       may be used to move up and down through text lines.  Text lines
       will scroll when the text cursor is moved into the top or bottom
       areas of the window.

Cursor Left/Right
       move the cursor one character left or right.  When the cursor
       moves to the left or right edge of the window, text will be
       scrolled to the right or left.

Ctrl/Cursor Left/Right
       may be used to scroll the text in the window left or right
       without moving the cursor.

Page Up/Down
       may be used to scroll up and down through source lines in
       increments of the number of lines in the window minus two.

Home   may be used to move to the first line of the text being viewed.

End    may be used to move to the last line of the text being viewed.

Enter  may be used to move the text cursor to the start of the next line
       of text.

"/"    may be used to search forwards for a string of text.  A prompt is
       displayed for the string to search.  The Cursor Up key may be
       used to fill in the previous search string.

"?"    may be used to search backwards for a string of text.  A prompt
       is displayed for the string to search.  The Cursor Up key may be
       used to fill in the previous search string.

"'"    (apostrophe) may be used to search forwards for the previously
       specified search string.

"      (quote) may be used to search backwards for the previously
       specified search string.

"."    (period) may be used to repeat the last action.

Escape
       may be used to terminate the viewing function.

"0" through "9"
       may be used to enter a number.  This number is used to repeat the
       next action the specified number of times.  For example, entering
       the number 20 followed by Cursor Down moves the cursor down 20
       lines rather than one.  For the Home and End keys, the number
       moves to "number" lines from the beginning of file and end of
       file, respectively.  To cancel a number without executing a
       command, press the Delete key.

Pressing one of the search keys causes a prompt for a search string to
appear.  If a previous string had been entered, this string may be
recalled using the Cursor Up key.  The recalled string will appear in
the prompt area.  Pressing the Escape key at this point will cancel the
search command.  The Cursor Left and Right keys and the Home, End,
Delete and Backspace keys may be used to edit the search string.  After
the search string has been entered, pressing the Enter key will begin
the search.  The search is done case insensitively, with the file
considered as a ring of text (e.g., if searching forwards and the end of
the file is reached without finding the text, the search continues from
the beginning of the file).  If the string is found, the cursor is
placed under the first matched character and the matched string is
highlighted.
::::LOG
┌──────────────────────────────────────────────────────────────────────┐
│ Log     [/Start | /Append | >] file_name                             │
│ >                                                                    │
└──────────────────────────────────────────────────────────────────────┘

The Log or > command may be used to log Dialogue window output to a
specified file.

/Start file_name This qualifier is used to start logging to the
       specified file.

       Example:
          DBG>log/start dbg.log
          DBG>>/start dbg.log

       The previous contents of the file are lost (overwritten).  When
       file_name is specified and no qualifier is specified then /Start
       is implied.

       Example:
          DBG>log dbg.log

       When neither the qualifier nor filename is specified then any
       currently opened log file is closed.

       Example:
          DBG>log

/Append file_name This qualifier is used to start logging and append
       logging records to the end of the specified file.

       Example:
          DBG>log/append dbg.log
          DBG>>/app dbg.log

> file_name This operator is a synonym for "/append".  Thus it behaves
       identically to the /Append qualifier

       Example:
          DBG>log > dbg.log
          DBG>>> dbg.log

If a log file is currently open, it must be closed before logging can be
done to a different file.  The current log file is closed if a Log
command is entered with no qualifier and filename.  The log file is
automatically closed when the debugger exits (see the description of the
Quit command).

Example:
   DBG>log/start debug.log

Output to the Dialogue window is also written to the file "debug.log".

Example:
   DBG>log/append debug.log
   DBG>log> debug.log
   DBG>>>debug.log
   DBG>>/append debug.log

The above examples are all equivalent forms of the Log/Append command.

Under QNX, a path specification that begins with a "/" could be
interpreted as a qualifier.

Example:
   DBG>log /users/fred/debug.log

In the above example, the "/users" qualifier is not supported and an
error will result.  To resolve this conflict, the /Start or /Append
qualifiers can be used.

Example:
   DBG>log /start /users/fred/debug.log
::::MENUS
VIDEO Menus
───────────

The Set menu on command may be used to cause a menu bar to appear at the
top of the screen.  Menus are provided as an alternative to some of the
more common VIDEO commands.  In the following sections, we explain how
to use menus and provide a brief synopsis of each menu.

Menu Selection
──────────────

Menu selection may be activated by pressing and releasing the Alt key.
The first menu item name or title is highlighted.

The cursor left and right keys may be used to highlight a particular
menu item.  The Enter key may be used to select the highlighted menu
item.  In some cases, the menu item opens up and a list of choices is
usually displayed.  In others, the menu item invokes an immediate
action.  The action menu items are identified by the "!" which is
appended to the menu title (e.g., Go!).  When a list of menu entries is
displayed, the list may be closed up by pressing the Escape key.  A
second press of the Escape key will return you to the Prompt window.

Alternately, direct selection of a menu item is possible by pressing
both the Alt key and the first letter shown in the menu name or title.
For example, the "Control" menu may be activated by pressing both the
"Alt" and "C" keys ("Alt" must already be depressed when you press the
"C" key).  If you have a mouse, you can do the same thing by moving the
mouse cursor to one of the menu items in the menu bar and depressing the
left mouse button.  If you then release the button, the currently
selected item will be performed.

Menus to the left or right of the current menu may be selected by using
the cursor left and right keys.  As you move left or right, only one
menu is activated.  With a mouse, you can do the same thing by dragging
the mouse through the various menu items in the menu bar.

If a menu opens up, one of the choices is highlighted.  This indicates
the current choice for that menu.  The cursor up and down keys may be
used to select a different choice.  With a mouse, different choices may
be selected by dragging the mouse to the desired item.  When an item has
been picked, the "Enter" key may be used to select it.  When using a
mouse, the left mouse button may be released.

The "Esc" key may be used to quit from a menu.  To quit from a menu with
a mouse, you can either:

   1. release the left button in an area outside of the menu, or
   2. click in an area outside of the menu.

The choice depends on the type of menu presented.

Some selections result in yet other menus being displayed.  The process
for making selections is the same.  Use the cursor left and right keys
to move left and right to other menus that may be shown.  Use the cursor
up and down keys to make a selection in each menu.  To signal that you
have made your selection, press the "Enter" key.  With a mouse you can
use the actions of dragging and clicking to make your selections.


The Control Menu
────────────────

Help   This entry is used to invoke VIDEO's "Help" system.

System This entry is used to start the system's command interpreter or
       "shell".  If you are using DOS, for example, then the
       "COMMAND.COM" program is run.  Certain conditions must be met
       before the shell can be run and these are listed in the
       description of the System command.

Restart This entry is used to restart the current application.  The
       application is reloaded into memory and execution is suspended at
       the program's entry point.  At this point, a VIDEO command such
       as "go main" may be entered.  See the description of the New
       /restart command for more information.

View   This entry is used to select a file for viewing.  See the
       description of the View command for more information.

Log    This entry is used to commence logging of VIDEO commands and
       responses to a file.  See the description of the Log command for
       more information.

Quit   This entry is used to quit from the debugger thereby terminating
       the current application.  See the description of the Quit command
       for more information.


The User Menu
─────────────

This is a user-definable list of menu items.  Each entry is created with
the Set menu add command.  An entry is a list of one or more VIDEO
commands.  Each new entry is labelled with a letter from the alphabet.
Thus a particular entry may be selected quickly by pressing the Alt key
and the letter corresponding to the desired entry.  The mouse can also
be used to select an entry.

Up to 20 items can be added to the "User" menu.


The Display Menu
────────────────

The text cursor can be moved directly to a particular window by using
this menu.  Select the window to which you wish to move the text cursor.
See the description of the Display command for more information.

The Paint Menu
──────────────

The colours for all windows or a particular window may be selected by
using menus.

When using a mouse, clicking on the "Sample" window is equivalent to
pressing the Enter key.

See the description of the Paint command for more information.


The Break! Menu
───────────────

Break points may be "set", "cleared", "activated" or "deactivated" when
"Break!" is chosen.  Two windows are displayed, one containing a set of
instructions and one containing a list of the break points currently
set.

You may press one of the keys "S", "C", "A" or "D" to select the desired
action.  The cursor up and down keys may be used to highlight individual
break points.

A mouse can be used on the list with the usual actions, clicking or
dragging to select a break point.  Clicking on the instruction box areas
acts as if the appropriate key has been pressed.  For example, clicking
on the quadrant that contains "s = set" acts as if the "S" key had been
pressed.  See the description of the Break command for more information.


The Watch! Menu
───────────────

Watch points may be "set", "cleared", "activated" or "deactivated" when
"Watch!" is chosen.  Two windows are displayed, one containing a set of
instructions and one containing a list of the watch points currently
set.  You may press one of the keys "S", "C", "A" or "D" to select the
desired action.  The cursor up and down keys may be used to highlight
individual watch points.

A mouse can be used on the list by the ordinary actions, clicking or
dragging to select a watch point.  Clicking on the instruction box areas
acts as if the appropriate key has been pressed.  For example, clicking
on the quadrant that contains "s = set" acts as if the "S" key had been
pressed.  See the description of the Watch command for more information.

The Trace! Menu
───────────────

Selecting the "Trace!" menu causes a Trace command (with default
arguments) to be executed.  Trace prompts appear in the prompt window.

If you have a mouse, you can click on the "hot-spots" in this window
instead of pressing a key.  For example, clicking on the "<i>" hot-spot
is equivalent to pressing the "I" key when selecting the "into" option
of trace.  See the description of the Trace command for more
information.

The Go! Menu
────────────

Selecting the "Go!" menu causes a Go command to be executed.  Program
execution is resumed at the current CS:IP (16-bit mode) or CS:EIP
(32-bit mode) location.  See the description of the Go command for more
information.
::::MODIFY
┌──────────────────────────────────────────────────────────────────────┐
│ Modify                                                               │
│     [/Byte]    [addr_expr] [ "," expr_list ]                         │
│     /Word      [addr_expr] [ "," expr_list ]                         │
│     /Dword     [addr_expr] [ "," expr_list ]                         │
│     /Pointer   [addr_expr] [ "," expr_list ]                         │
│     /IOByte    [port_expr] [ "," expr_list ]                         │
│     /IOWord    [port_expr] [ "," expr_list ]                         │
│     /IODword   [port_expr] [ "," expr_list ]                         │
└──────────────────────────────────────────────────────────────────────┘

The Modify command is used to modify the contents of memory in one of
several different ways.

/Byte [addr_expr] [ "," expr_list ] The starting address addr_expr
       identifies the beginning of a sequence of 8-bit values (bytes).
       Each value that you specify is stored modulo 256 (0x100).

/Word [addr_expr] [ "," expr_list ] The starting address addr_expr
       identifies the beginning of a sequence of 16-bit values (words).
       Each value that you specify is stored modulo 65,536 (0x10000).

/Dword [addr_expr] [ "," expr_list ] The starting address addr_expr
       identifies the beginning of a sequence of 32-bit values
       (doublewords).  Each value that you specify is stored modulo
       4,294,967,296 (0x100000000).

/Pointer [addr_expr] [ "," expr_list ] The starting address addr_expr
       identifies the beginning of a sequence of segment/offset pairs
       (segment:offset).  In 16-bit mode, each value in the pair that
       you specify is stored modulo 65536 (0x10000).  In 32-bit mode,
       each value in the pair that you specify is stored modulo
       4,294,967,296 (0x100000000).  If you do not specify the segment
       value, the current contents of the DS register is used.

/IOByte [port_expr] [ "," expr_list ] The starting port address
       port_expr identifies the beginning of a sequence of 8-bit ports
       (bytes).  Each value that you specify is written to the port
       modulo 256 (0x100).

/IOWord [port_expr] [ "," expr_list ] The starting port address
       addr_expr identifies the beginning of a sequence of 16-bit ports
       (words).  Each value that you specify is written to the port
       modulo 65,536 (0x10000).

/IODword [port_expr] [ "," expr_list ] The IODword qualifier is
       supported on 386 systems or higher.  The starting port address
       addr_expr identifies the beginning of a sequence of 32-bit ports
       (doublewords).  Each value that you specify is written to the
       port modulo 4,294,967,296 (0x100000000).

If you do not specify a qualifier, the default is /Byte.  If you do not
specify a list of values, VIDEO will prompt for values until an empty
line is entered.  If you do not want to modify a location but want VIDEO
to continue prompting, you can enter a slash ("/") to indicate that the
current value is to be retained.  When specifying a list of values, a
location can be skipped by omitting the value (i.e., a consecutive pair
of commas is entered).

Example:
   DBG>modify 0x200,1,2,3
   DBG>modify/byte 0x200,1,2,3

In the above equivalent examples, memory locations DS:200, DS:201 and
DS:202 are modified with the values 1, 2 and 3.

Example:
   DBG>modify 0x200,1,,3

In the above example, memory locations DS:200 and DS:202 are modified
with the values 1 and 3.

Example:
   DBG>modify/word 304
   2335:0304= 0001 :- 0x100
   2335:0306= 1323 :- 0x101
   2335:0308= 8730 :- 0x102
   2335:030A= 0020 :-

In the above example, VIDEO prompts for new word values to replace
memory locations DS:304, DS:306, DS:308 and DS:30A.  Memory location
DS:30A is left unmodified by simply pressing the Enter key in response
to the prompt.

Example:
   DBG>modify/word 0x304
   2335:0304= 0001 :- 0x100
   2335:0306= 1323 :- /
   2335:0308= 8730 :- 0x102
   2335:030A= 0020 :-

In the above example, VIDEO prompts for new word values to replace
memory locations DS:304, DS:306, DS:308 and DS:30A.  Memory location
DS:306 is left unmodified by simply entering a "/" in response to the
prompt.

Example:
   DBG>modify/pointer _jmptable
   _jmptable= 2223:0602 :- &test1
   _jmptable+04 = 2223:06BE :- &test2
   _jmptable+08 = 2223:0743 :- &test3
   _jmptable+0A = 2223:07B7 :- &test4
   _CMAIN_ = 5756:5153 :-

In the above 16-bit example, VIDEO prompts for new segment:offset values
to replace consecutive memory locations identified by the label
_jmptable.  The values supplied are the addresses of four different
routines (the & operator yields the segment/offset values for the
specified location).  The memory location identified as _CMAIN_ is left
unmodified by simply pressing the Enter key in response to the prompt.

Example:
   DBG>modify/iobyte 0x3F9,0x0D,0x01,0x03,0x0B

In the above example, ports 3F9, 3FA, 3FB and 3FC are modified with the
hexadecimal values 0D, 01, 03 and 0B.

Example:
   DBG>modify/ioword 0x2f8
   02F8= 000D :- 0x000E
   02FA= 0301 :- 0x0302
   02FC= 630B :- 0x630A
   02FE= 0000 :-

In the above example, VIDEO prompts for new word values to store in
ports 2F8, 2FA, 2FC, and 2FE.  Port 2FE is left unmodified by simply
pressing the Enter key in response to the prompt.
::::MOUSE
Window Manipulation with a Mouse
────────────────────────────────

Installing a Mouse Driver Under DOS
───────────────────────────────────

In order to use a mouse with VIDEO, you must install the IBM Mouse
Driver program that is supplied with the IBM Mouse.  Alternatively, you
may use a mouse and mouse driver that are compatible with the IBM Mouse
and IBM Mouse Driver.  The IBM Mouse Driver is installed by running the
"MOUSE.COM" program.

Example:
   C>\dos\mouse


Installing a Mouse Driver Under QNX
───────────────────────────────────

In order to use a mouse with VIDEO, you must install a mouse driver
program.  See your QNX manuals for further information on mouse
installation.


Using a Mouse with VIDEO
────────────────────────

VIDEO supports the use of a mouse in many ways.  Most actions are
selected by "clicking" the mouse at the desired location.  This is done
by moving the mouse cursor, the solid rectangle on the screen, to a
place on the screen and then pressing the left button on the mouse.

The mouse cursor can be positioned to any window.  In some windows, such
as the "Source" and "Assembly" windows, text may be scrolled up or down,
left or right, by "dragging" the mouse.  This is done by moving the
mouse cursor to a line in the window and, while pressing down the left
button on the mouse, repositioning the mouse cursor to another place in
the window.

To scroll text up or down by dragging the mouse, vertical scrolling must
be enabled.  This is done by clicking the mouse on the scroll bar at the
right side of the window where the word "Locked" appears.  If the word
"Locked" does not appear then vertical scrolling is already enabled.
Vertical scrolling can be enabled/disabled by clicking on the scroll bar
again.

To scroll text left or right by dragging the mouse, horizontal scrolling
must be enabled.  This is done by clicking the mouse on the scroll bar
at the bottom of the window where the word "Locked" appears.  If the
word "Locked" does not appear then horizontal scrolling is already
enabled.  Horizontal scrolling can be enabled/disabled by clicking on
the scroll bar again.

The entire window can be repositioned on the screen by dragging the
window's title line to a new place on the screen.

Some actions are accomplished by "double-clicking" the left mouse
button.  Double-clicking is done by rapidly pressing the left mouse
button twice at the same location without moving the mouse cursor.
These actions are described in subsequent sections.

Text selection may be engaged by pressing the right-hand mouse button.
Without releasing the button, the mouse cursor may be moved about the
screen to highlight a sequence of text (characters, words, expressions,
etc.).  When the right-hand mouse button is released, the Action window
appears on the screen.  If the right-hand mouse button is pressed and
released without moving the mouse, the "item" under the mouse cursor is
selected in its entirety and the Action window appears on the screen.

When the "Show source" entry is selected, the source/assembly code
corresponding to the selected text is displayed in the Source and
Assembly windows (if present on the screen).

A line appears in the Dialogue window that indicates the address of the
previous source/assembly code and the new source/assembly code under
examination.

Example:
   0x65CB:0x0012 => ClearScreen

You can use this entry to return to the previous location by
highlighting the address that is displayed on the left of the "=>" using
the right-hand mouse button.  In the above example, this would be the
entry "0x65CB:0x0012" (the segment and offset of the previous location
under examination).

When using a mouse, many windows have "gadgets".

   1. The "scroll up" and "scroll down" gadgets may be used to
      scroll text vertically.

   2. The "scroll left" and "scroll right" gadgets may be used
      to scroll text horizontally.

   3. The "page up" and "page down" gadgets (small triangle shapes at
      the right of the window) perform different actions depending on
      the window.

   4. The "page left" and "page right" gadgets (small triangle shapes at
      the bottom of the window) perform different actions depending on
      the window.

   5. The "window zoom" gadget (the sunburst symbol, in the top, right
      corner of the window) may be used to zoom the active window
      between its normal size and the size of entire screen.

      If you place the mouse cursor on the "zoom" gadget and press the
      right-hand mouse button, the window will temporarily zoom to full
      size.  When you release the button, the window will return to its
      normal size.

   6. The "window resize" gadget (double arrow, in the bottom, right
      corner) may be used to enlarge or shrink a window.

   7. The "window close" gadget (triple bar, in the top, left corner)
      may be used to remove a window from the screen.

If you click on a "scroll" or "page" gadget, the associated action is
performed once.  If you hold the left mouse button down while positioned
on one of these gadgets, the associated action is performed repeatedly.
If you drag the "window resize" gadget, the window to which it belongs
is grown or shrunk.


Manipulating the Assembly Window with a Mouse
─────────────────────────────────────────────

   1. Clicking in the Assembly window causes the text cursor to move to
      this window.  It becomes the "active" window.

   2. Assembly instructions may be scrolled up or down by dragging the
      mouse.  To do this, the right-side scrolling bar must be unlocked.

   3. Assembly instructions may be scrolled left or right by dragging
      the mouse.  To do this, the bottom scrolling bar must be unlocked.

   4. Gadgets are provided for scrolling, resizing, zooming and closing
      the Assembly window.

   5. The "scroll up" and "scroll down" gadgets may be used to move up
      and down through text lines.  When the text cursor moves to the
      top or bottom of the window, text will be scrolled down or up.

   6. The "scroll left" and "scroll right" gadgets move the cursor one
      character left or right.  When the text cursor moves to the left
      or right edge of the window, text will be scrolled to the right or
      left.

   7. The "page up" and "page down" gadgets may be used to scroll up and
      down through assembly instructions in increments of the number of
      lines in the window minus two.

   8. Clicking on an assembly instruction in the Assembly window makes
      it the current assembly instruction.  This line is displayed in
      "standout" attributes.  The value of the VIDEO variable dbg$code
      changes to reflect the change in the current assembly instruction.
      This variable reflects the segment:offset of the most recent code
      location to be examined.  In addition, the "." address is changed
      to point to the assembly instruction.  The "." address is used in
      many VIDEO commands.

      Example:
         do [CS IP] = .
             or
         do [CS EIP] = .

      In the above example, the contents of the CS:IP or CS:EIP register
      pair are modified to point to the current assembly instruction.

   9. Double-clicking on a line will set or clear a breakpoint at the
      assembly instruction.


Manipulating the Command Window with a Mouse
────────────────────────────────────────────

Clicking in the Command window causes the text cursor to move to the
window and the window to be refreshed.  It becomes the "active" window.

Manipulating the Dialogue Window with a Mouse
─────────────────────────────────────────────

   1. Clicking in the Dialogue window causes the text cursor to move to
      this window.  It becomes the "active" window.

   2. Text may be scrolled up or down by dragging the mouse.  To do
      this, the right-side scrolling bar must be unlocked.

   3. Text may be scrolled left or right by dragging the mouse.  To do
      this, the bottom scrolling bar must be unlocked.

   4. Gadgets are provided for scrolling, resizing, and zooming the
      Dialogue window.

   5. The "scroll up" and "scroll down" gadgets may be used to move up
      and down through text lines.  When the text cursor moves to the
      top or bottom of the window, text will be scrolled down or up.

   6. The "scroll left" and "scroll right" gadgets move the cursor one
      character left or right.  When the text cursor moves to the left
      or right edge of the window, text will be scrolled to the right or
      left.

   7. The "page up" and "page down" gadgets may be used to scroll up and
      down through Dialogue window output in increments of the number of
      lines in the window minus two.

Manipulating the FPU Window with a Mouse
────────────────────────────────────────

   1. Clicking in the FPU window causes the text cursor to move to this
      window.  It becomes the "active" window.  The text cursor may be
      positioned to any register contents or flag bits display.

   2. Double-clicking on a register display (ST(0), ST(1), etc.) will
      cause a register modification window to be displayed on the
      screen.  A new value may be entered or the register may be left
      unmodified by just pressing the Enter key in response to the
      prompt.

      Double clicking on a flag causes its value to be complemented.

   3. The "scroll up" gadget may be used to move backwards through
      register sets to the oldest register set.

   4. The "scroll down" gadget may be used to move forwards through
      register sets to the most recent register set.

   5. The "page up" gadget may be used to move backwards through
      register sets to the oldest register set.

   6. The "page down" gadget may be used to move forwards through
      register sets to the most recent register set.


Manipulating the Memory Window with a Mouse
───────────────────────────────────────────

   1. Clicking in the Memory window causes the text cursor to move to
      this window.  It becomes the "active" window.  The text cursor may
      be positioned to any memory entry shown in the window.

   2. Memory entries may be scrolled up or down by dragging the mouse.
      To do this, the right-side scrolling bar must be unlocked.

   3. The "scroll up" and "scroll down" gadgets may be used to scroll up
      and down through memory.

   4. The "page up" and "page down" gadgets may be used to scroll up and
      down through memory in increments of the number of lines in the
      window minus two.

   5. Clicking on the "(Ins)" entry will cause the display to change
      between 8-bit bytes, 16-bit words, and 32-bit doublewords.  When
      8-bit bytes are displayed, their ASCII equivalents are also
      displayed on the right-hand side of the window.

   6. Clicking on the "(Del)" entry may be used to select a new memory
      location to be displayed.  A prompt window appears for the new
      memory location.  A new value may be entered or the memory address
      may be left unmodified by just pressing the Enter key in response
      to the prompt.

   7. Clicking on the "HOME" entry may be used to move directly to the
      original location of memory that was requested to be displayed.

   8. Double-clicking on a memory location will cause a memory
      modification window to be displayed on the screen.  A new value
      may be entered or the memory location may be left unmodified by
      just pressing the Enter key in response to the prompt.


Manipulating the Prompt Window with a Mouse
───────────────────────────────────────────

Clicking in the Prompt window causes the text cursor to move to this
window.  It becomes the "active" window and VIDEO commands may be
entered.

Manipulating the Register Window with a Mouse
─────────────────────────────────────────────

   1. Clicking in the Register window causes the text cursor to move to
      this window.  It becomes the "active" window.  The text cursor may
      be positioned to any register contents or flag bits display.

   2. Double-clicking on a register display will cause a register
      modification window to be displayed on the screen.  A new value
      may be entered or the register may be left unmodified by just
      pressing the Enter key in response to the prompt.

      Double clicking on a flag causes its value to be complemented.

   3. The "scroll up" gadget may be used to move backwards through
      register sets to the oldest register set.

   4. The "scroll down" gadget may be used to move forwards through
      register sets to the most recent register set.

   5. The "page up" gadget may be used to move backwards through
      register sets to the oldest register set (same as "scroll up").

   6. The "page down" gadget may be used to move forwards through
      register sets to the most recent register set (same as "scroll
      down").

Manipulating the Source Window with a Mouse
───────────────────────────────────────────

   1. Clicking in the Source window causes the text cursor to move to
      this window.  It becomes the "active" window.

   2. Source lines may be scrolled up or down by dragging the mouse.  To
      do this, the right-side scrolling bar must be unlocked.

   3. Source lines may be scrolled left or right by dragging the mouse.
      To do this, the bottom scrolling bar must be unlocked.

   4. Gadgets are provided for scrolling, resizing, zooming and closing
      the Source window.

   5. The "scroll up" and "scroll down" gadgets may be used to move up
      and down through text lines.  When the text cursor moves to the
      top or bottom of the window, text will be scrolled down or up.

   6. The "scroll left" and "scroll right" gadgets move the scroll one
      character left or right.  When the text cursor moves to the left
      or right edge of the window, text will be scrolled to the right or
      left.

   7. The "page up" and "page down" gadgets may be used to scroll up and
      down through source lines in increments of the number of lines in
      the window minus two.

   8. Clicking on a source line in the Source window makes it the
      current line.  This line is displayed in "standout" attributes.

      The value of the VIDEO variable dbg$code changes to reflect the
      change in the current line.  This variable reflects the
      segment:offset of the most recent code location to be examined.
      In addition, the "." address is changed to point to the first
      assembly instruction for the source line.  If there are no
      assembly instructions for the source line (as in lines or
      declarative lines) then the "." address is positioned to an
      earlier line (or the first line) in the module which has assembly
      instructions.  The "." address is used in many VIDEO commands.

      Example:
         do [CS IP] = .
             or
         do [CS EIP] = .

      In the above example, the contents of the CS:IP or CS:EIP register
      pair are modified to point to the current source line.

   9. Double-clicking on a line will set or clear a breakpoint at the
      first assembly instruction for the source line.


Manipulating the Stack Window with a Mouse
──────────────────────────────────────────

   1. Clicking in the Stack window causes the text cursor to move to
      this window.  It becomes the "active" window.  The text cursor may
      be positioned to any stack entry.

   2. Stack entries may be scrolled up or down by dragging the mouse.
      To do this, the right-side scrolling bar must be unlocked.

   3. The "scroll up" and "scroll down" gadgets may be used to scroll up
      and down through the stack.

   4. The "page up" and "page down" gadgets may be used to scroll up and
      down through the stack in increments of the number of lines in the
      window minus two.

   5. Clicking on the "(Ins)" entry will cause the display to change
      between 8-bit bytes, 16-bit words, and 32-bit doublewords.  When
      8-bit bytes are displayed, their ASCII equivalents are also
      displayed on the right-hand side of the window.

   6. Clicking on the "HOME" entry may be used to move directly to the
      stack entry referenced by SS:SP (16-bit mode) or SS:ESP (32-bit
      mode).

   7. Double-clicking on a stack entry will cause a stack modification
      window to be displayed on the screen.  A new value may be entered
      or the stack entry may be left unmodified by just pressing the
      Enter key in response to the prompt.


Manipulating the Thread Window with a Mouse
───────────────────────────────────────────

   1. Clicking in the Thread window causes the text cursor to move to
      this window.  It becomes the "active" window.  The text cursor may
      be positioned to any thread entry.

   2. The "scroll up" and "scroll down" gadgets may be used to scroll up
      and down through thread entries.

   3. The "page up" and "page down" gadgets may be used to scroll up and
      down through thread entries in increments of the number of lines
      in the window minus two.

   4. Double-clicking on a thread "id" field will cause that thread to
      become the current thread.  The other windows on the screen will
      change to reflect the selection of another execution thread.

      Double-clicking on a "state" field will cause that thread's state
      to become either "frozen" or "runnable".


Manipulating the Variable Window with a Mouse
─────────────────────────────────────────────

   1. Clicking in the Variable window causes the text cursor to move to
      this window.  It becomes the "active" window.

   2. Fields can be selected and viewed by clicking on them.

   3. If you click on the line of dashes in the window, you will ascend
      to previous levels.

   4. Gadgets are provided for scrolling, resizing, zooming and closing
      the Variable window.

   5. The "scroll up" and "scroll down" gadgets may be used to move up
      and down through the fields of a structure.  Entries that
      represent structures are displayed by using "{...}".  Entries that
      represent arrays are displayed by using "(...)".

   6. The "page up" and "page down" gadgets may be used to scroll up and
      down through the Variable window in increments of the number of
      lines in the window.


Manipulating the View Window with a Mouse
─────────────────────────────────────────

   1. Clicking in the View window causes the text cursor to move to the
      mouse cursor.

   2. Text lines may be scrolled up or down by dragging the mouse.  To
      do this, the right-side scrolling bar must be unlocked.

   3. Text lines may be scrolled left or right by dragging the mouse.
      To do this, the bottom scrolling bar must be unlocked.

   4. Gadgets are provided for scrolling and closing the View window.

   5. The "scroll up" and "scroll down" gadgets may be used to move up
      and down through text lines.  When the text cursor moves to the
      top or bottom of the window, text will be scrolled down or up.

   6. The "scroll left" and "scroll right" gadgets move the scroll one
      character left or right.  When the text cursor moves to the left
      or right edge of the window, text will be scrolled to the right or
      left.

   7. The "page up" and "page down" gadgets may be used to scroll up and
      down through source lines in increments of the number of lines in
      the window minus two.
::::NEW
┌──────────────────────────────────────────────────────────────────────┐
│ NEW                                                                  │
│     [/Restart]     [prog_parms]                                      │
│     /Program       [:sym_file] program_name [prog_parms]             │
│     /STDIn         [file_name]                                       │
│     /STDOut        [file_name]                                       │
│     /SYmbol        sym_file [expr_list]                              │
└──────────────────────────────────────────────────────────────────────┘

The NEW command is used to initialize various items.

/Restart [prog_parms] This qualifier is used to reload the current
       application and place it into an initial state where execution
       may be started over again.  The application may have undergone
       partial or complete execution.  If desired, a new command line
       may be specified for the application.

          prog_parms ::= prog_cmd_line | "{"prog_cmd_line"}"

       You must use "{" and "}" when you have a ";" in the command line
       since VIDEO uses the semicolon as a command separator.

       Example:
          DBG>new {Today is Tuesday}

       The /Restart qualifier is implied when no other qualifier is
       specified.

       Under QNX, a path specification that begins with a "/" could be
       interpreted as a qualifier.

       Example:
          DBG>new /users/fred/test.dat

       In the above example, the "/users" qualifier is not supported and
       an error will result.  To resolve this conflict, the /Restart
       qualifier must be used.

       Example:
          DBG>new/restart /users/fred/test.dat

/Program [:sym_file] program_name [prog_parms] This qualifier is used to
       load a new application and place it into an initial state where
       execution may be started.

       If the symbolic debugging information for the program has been
       placed in a separate file, this file can be specified.  The
       specification must be preceded by a colon (":").  The default
       file extension or suffix of the symbol file is ".sym".  The
       symbolic information file can be produced by the WATCOM Linker or
       by the WATCOM Strip Utility.

       If desired, a command line may be specified for the new
       application.

          prog_parms ::= prog_cmd_line | "{"prog_cmd_line"}"

       You must use "{" and "}" when you have a ";" in the command line
       since VIDEO uses the ";" as a command separator.

       Example:
          DBG>new/prog echo {Today is Tuesday}

       Any break or watch points which may have been active are
       deactivated.

       The specification program_name has the same format as the VIDEO
       command line.  For DOS, OS/2 and NetWare 386 systems, the format
       is:

          [d:][path]filename[.ext]

       For QNX, the format is:

          [//nid] [//node][path]filename

       The semantics for locating and loading a program are identical to
       that described in the chapters dealing with the use of VIDEO
       under a particular operating system.

/STDIn [file_spec] This qualifier can be used to associate the standard
       input file handle with a particular file or device.  This is
       similar to specifying <file_spec on the command line.  When
       file_spec is omitted, the standard input file handle is restored
       to its original state.

       Note that the following command does not produce the effect that
       might be anticipated.

       Example:
          DBG>new/prog testit <input.fil

       Instead, the string "<input.fil" will be passed as a parameter to
       the program.  To accomplish the desired effect, the following two
       commands must be issued.

       Example:
          DBG>new/prog testit
          DBG>new/stdin input.fil

/STDOut [file_spec] This qualifier can be used to associate the standard
       output file handle with a particular file or device.  This is
       similar to specifying >file_spec on the command line.  When
       file_spec is omitted, the standard output file handle is restored
       to its original state.

       Note that the following command does not produce the effect that
       might be anticipated.

       Example:
          DBG>new/prog hello >output.log

       Instead, the string ">output.log" will be passed as a parameter
       to the program.  To accomplish the desired effect, the following
       two commands must be issued.

       Example:
          DBG>new/prog hello
          DBG>new/stdout output.log

/SYmbol sym_file [expr_list] This qualifier is used to load additional
       symbolic debugging information and specify the mapping between
       the linker addresses and the actual execution addresses.  This
       feature is useful when debugging Terminate-and-Stay-Resident
       (TSR) programs under DOS, when debugging FoxPro External
       Routines, when debugging AutoCAD ADS programs, or other similar
       situations.

       The default file extension or suffix of the symbol file is
       ".sym".  The symbolic information file can be produced by the
       WATCOM Linker or by the WATCOM Strip Utility.

       The specification sym_file is system dependent.  For DOS, OS/2
       and NetWare 386 systems, the format is:

          [d:][path]filename[.ext]

       For QNX, the format is:

          [//node][path]filename

       The optional expression list expr_list varies according to the
       type of application that you are debugging.  For 16-bit,
       real-mode applications (e.g., DOS):

          new/symbol sym_file seg1

       seg1 is the base address (segment:offset) of the program.

       For 32-bit, protect-mode "flat model" applications (e.g., DOS
       Extenders, 32-bit Windows, 32-bit OS/2):

          new/symbol sym_file seg1, seg2
        seg1 is the loaded code segment:offset of the program.  seg2 is
       the data/extra/stack segment alias for the loaded code segment
       (in the "flat" model, segments CS, DS, ES, SS all map to the same
       linear address but will have different selector values).

       For 16- or 32-bit, protect-mode segmented applications (e.g.,
       16-bit Windows, 16-bit OS/2, QNX):

          new/symbol sym_file seg1, seg2, seg3, ...
        segN is the loaded segment:offset value for the N'th segment of
       the program.

       If segN is a simple integer (e.g., 5), it is assumed to represent
       a segment value and the offset portion is assumed to be 0.  If
       seg:off is specified (e.g., 5:100) then "seg" is the loaded
       segment value and "off" is added to all symbol address offsets.

       If you do not specify all the required loaded segment values then
       the debugger will begin prompting for the missing values.

       For examples of the NEW /SYmbol command, see the VIDEO command
       file ADS.DBG or FOX.DBG.

       When debugging DOS applications locally, it may be necessary to
       specify the VIDEO "REServesym" option when starting up the
       debugger.  For example, you may get the message "no memory for
       symbolic information".  This indicates that the option must be
       specified.
::::NOTATION
The following notation is used to describe the syntax of VIDEO commands.

Abc    The short form for the item abc is a.  For example, if the item
       is "COMPute", the valid forms are "comp", "compu", "comput" and
       "compute".

[abc]  The item abc is optional.

{abc}  The item abc may be repeated zero or more times.

"abc"  The characters abc are required.

a|b|c  One of a, b or c may be specified.

a ::= b The item a is defined in terms of b.

To test your understanding of the above notation, consider the following
example.

   dec_digit ::= "0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9"

In the above example, a decimal digit (dec_digit) is defined as one of
the characters "0" through "9" (a "0" or a "1" or a "2", etc.).  We
could then define a decimal number to be

   decimal_number ::= dec_digit {dec_digit}

This is read as "a decimal number is defined to be a decimal digit
followed by zero or more decimal digits".  Clearly, "12345" conforms to
our rule whereas "12ABC" and "Hello" do not.

We also use several abbreviated terms in the description of VIDEO
commands.

Short Form Explanation

addr   "address"
arg    "argument"
brk    "break", "break point"
char   "character"
cmd    "command"
expr   "expression"
num    "number"
parm   "parameter"
prog   "program"
reg    "register"
spec   "specifier"
tmp    "temporary"

We also concatenate these abbreviations by using the underscore to
define new abbreviations.

Examples:

addr_expr "address expression"

cmd_spec "command specifier"

Several commands may be entered on one line by separating them with
semicolons.

Example:
   DBG>do myvar=var*2;print myvar

In the above example, the first command sets the variable myvar to twice
the value of var and the second command prints this new value.

Using our notation, we define a command line as follows:

   cmd_line ::= [cmd] { ";" [cmd] }

While such definitions may be quite precise, they often tend to be
somewhat more obscure.  If we analyze the definition carefully, we will
discover that an empty line qualifies as a command.  In the following
sections, we will first present the concise command syntax.  This is
followed by an explanation of both the syntax and semantics of the
command.  A number of examples are also presented so that you may get a
"feel" for the command's syntax.
::::OS2_STARTUP
┌──────────────────────────────────────────────────────────────────────┐
│ WVIDEO [options] [:sym_file] file_spec [cmd_line]                    │
└──────────────────────────────────────────────────────────────────────┘

The square brackets [ ] denote items which are optional.

WVIDEO is the program name for VIDEO.

options is a list of valid VIDEO options, each preceded by a dash ("-")
       or a slash ("/").  Options may be specified in any order.

sym_file is an optional symbolic debugging information file
       specification.  The specification must be preceded by a colon
       (":").  For OS/2, the syntax of sym_file is:

       [d:][path]filename[.ext]

       The default file extension of the symbol file is ".SYM".

       The symbolic information file can be produced by the WATCOM
       Linker WLINK or by the WATCOM Strip Utility WSTRIP.

file_spec is the file name of the file to be loaded into memory.  For
       OS/2, the syntax of file_spec is:

       [d:][path]filename[.ext]

       d:     is an optional drive specification such as "A:", "B:",
              etc.  If not specified, the default drive is assumed.

       path   is an optional path specification such as "\UTILS\BIN\".

       filename is the file name of the file to be loaded into memory.

       ext    is the file extension of the file to be loaded into
              memory.  A null file extension may be specified by typing
              the period "." but not the extension.  If no file
              extension is specified (i.e., both the period and
              extension are omitted), the default is ".EXE".

cmd_line is an optional command line which will be passed on to the
       application.

If both drive and path are omitted, VIDEO will first attempt to locate
the file in the current directory of the default drive.  If this fails,
VIDEO will search for the file in each path listed in the PATH
environment string.


Command Line Options
────────────────────

┌──────────────────────────────────────────────────────────────────────┐
│     /Dynamic=space                                                   │
│     /NOFpu                                                           │
│     /Invoke=file_spec                                                │
│     /Lines=number                                                    │
│     /NOInvoke                                                        │
│     /NOMouse                                                         │
│     /Registers=number                                                │
│     /REMotefiles                                                     │
│     /NOSymbols                                                       │
│     /TRap=trap_file[;trap_parm]                                      │
└──────────────────────────────────────────────────────────────────────┘

Options may be specified in any order.  Short forms may be specified for
options and are shown above in capital letters.  If "space" is suffixed
with the letter "K" then "space" refers to multiples of 1K bytes (1024
bytes).  If "space" is suffixed with the letter "B" then "space" refers
to the number of bytes.  If no suffix is specified and "space" is a
number less than 1000 then "space" is assumed to refer to multiples of
1K bytes (1024 bytes); otherwise it refers to the number of bytes.

/Dynamic=number specifies the initial amount of dynamic storage that
       VIDEO is to reserve for items such as windows, user-defined
       symbols, etc.  The default amount that is set aside is 20480
       bytes (20 Kilobytes).  As additional storage is required, VIDEO
       will allocate it.

/NOFpu requests that the debugger ignore the presence of a math
       coprocessor.  No memory will be allocated by the debugger for
       saving the context of the 80x87 numeric data processor.  Use this
       option if your application will not use the math coprocessor and
       you wish to reduce the amount of memory required by the debugger.

/Invoke=file_spec may be used to specify an alternate name for the
       debugger command file which is to be automatically invoked at
       start-up time.  The default file name is "PROFILE.DBG".  VIDEO
       command files are found in the current directory or one of the
       directories listed in the OS/2 PATH environment string.

/Lines=number may be used to specify the number of display lines that
       VIDEO is to use.  If this option is not specified, the default
       number of output lines is selected.  When an Enhanced Graphics
       Adapter (EGA) is present, 43 lines of output may be requested.
       When an Video Graphics Array (VGA) is present, 28 or 50 lines of
       output may be requested.

/NOInvoke specifies that the default debugger command file is not to be
       invoked.

/NOMouse requests that the debugger ignore any attached mouse.

/Registers=number may be used to specify how many register sets to set
       aside for the recording of register contents.  The default number
       of register sets is 2.  See the description of the Register
       command for more information (this command is described under the
       "REGISTER" topic).

/REMotefiles may be used in conjunction with the remote debugging
       capabilities of the debugger.  Remote debugging involves using
       two personal computers.  One, called the "task machine", is used
       to run the application; the other, called the "debugger machine",
       is used to run the debugger.  When REMotefiles is specified, all
       debugger files (except "trap" files) and application source files
       are opened on the task machine rather than the debugger machine
       (if you are doing local debugging, these two machines are
       actually the same).  The "trap" file must be located on the
       debugger machine because it contains the code to open files on
       the task machine.

       Note that the PATH environment variable on the task machine is
       always used in locating executable image files.  When REMotefiles
       is specified, the debugger also uses the task machine's PATH
       environment variable to locate debugger command files.

/NOSymbols requests that VIDEO omit all debugging information when
       loading an executable image.  Information regarding global and
       local symbol names, data types, and line numbers is not
       processed.

/TRap=trap_file[;trap_parm] may be specified when debugging an
       application on a remote machine.  You must specify the name of
       one of the "trap" files provided with VIDEO.  Under OS/2, the
       file extension defaults to ".DLL".  The "BINP\DLL" directory
       contains the dynamic link libraries (DLL) provided with VIDEO.
       The OS/2 LIBPATH directive in the "CONFIG.SYS" file must be used
       to identify the location of the "DLL" trap files.

       Under OS/2, if you do not specify a trap file, the default trap
       file "STD.DLL" will be loaded.  This interface module supports
       debugging on the local computer system running OS/2.  No remote
       debugging is possible.
::::PAINT
┌──────────────────────────────────────────────────────────────────────┐
│ PAint (window_name | ["*"]) attr_name [ fg_col ["," bg_col] ]        │
└──────────────────────────────────────────────────────────────────────┘

The PAint command is used to define the colour composition of windows.
The valid window names are:

   Assembly
   Command
   Dialogue
   Fpu
   Memory
   Prompt
   Register
   SOurce
   STack
   Thread

An asterisk ("*") may be used to denote all of them.  If a window name
is omitted then "*" is assumed.

Five different attributes of a window may be individually coloured.  The
attribute attr_name may be one of:

   Plain
   Active
   Standout
   Title
   Gadget

Foreground (fg_col) and background (bg_col) colours may be selected from
the following:

   BLAck
   BLUe
   GREEn
   Cyan
   Red
   Magenta
   BROwn
   White

In addition, the following foreground colour variations may be selected:

   BRIght BLAck
   BRIght BLUe
   BRIght GREEn
   BRIght Cyan
   BRIght Red
   BRIght Magenta
   BRIght BROwn
   BRIght White
   GRAy
   GREY
   Yellow

"GRAy" and "GREY" are synonyms for "BRIght BLAck".  "Yellow" is a
synonym for "BRIght BROwn".  The "BLINking" keyword may be also precede
a foreground colour to specify that the item should also blink when it
is displayed.  Please note that colour attributes on the IBM Monochrome
Display and Printer Adapter will behave as described in the following
table.

Colour Monochrome

black  (invisible)
blue   underlined white
green  white
cyan   white
red    white
magenta white
brown  white
white  white
bright black (invisible)
bright blue bright white
bright green white
bright cyan white
bright red white
bright magenta white
bright brown white
bright white white

When specifying colour attributes for a window item, the foreground
colour is specified first and the background colour last.  If one of the
foreground or background colours is omitted, it will remain unchanged.
Note that the background colour specification is always preceded by a
comma.

Attributes: Description:

Plain  Each window displays "plain" text.  This text usually forms the
       greater part of a window.

       Example:
          DBG>paint * plain white,blue

       In the above example, the plain text of all windows is set to
       white characters on a blue background.

       Example:
          DBG>paint assembly plain bright green,red

       In the above example, the plain text of the Assembly window only
       is set to bright green characters on a red background.

Active Some items in a window may be highlighted in the "active" colour
       combination.  For example, the source line or assembler
       instruction that is about to be executed is displayed in the
       "active" colour attributes.

       Example:
          DBG>paint * active bright white,blue

       In the above example, the "active" text of all windows is set to
       bright white characters on a blue background.

       Example:
          DBG>paint source active cyan,brown

       In the above example, the "active" text of the Source window only
       is set to cyan characters on a brown background.

Standout Some items in a window may be highlighted with the "standout"
       colour combination.  For example, the source line or assembler
       instruction that is displayed by using the Examine /Source
       command is displayed in the "standout" colour attributes.

       Example:
          DBG>paint * standout red,white

       In the above example, the "standout" text for all windows is set
       to red characters on a white background.

       Example:
          DBG>paint source standout brown,cyan

       In the above example, the "standout" text of the Source window
       only is set to brown characters on a cyan background.

Title  Each window may be titled and the colours for the title line may
       be selected.

       Example:
          DBG>paint * title yellow,magenta

       In the above example, the title lines for all windows bearing
       titles are displayed with yellow characters on a magenta
       background.

       Example:
          DBG>paint assembly title magenta,green

       In the above example, if there is a title line for the Assembly
       window then it will be displayed with magenta characters on a
       green background.

Gadget Mouse window gadgets are displayed in the "gadget" colour
       combination.

       Example:
          DBG>paint * gadget black, cyan

       In the above example, the "gadget" colours for all windows is set
       to black characters on a cyan background.
::::PRINT
┌──────────────────────────────────────────────────────────────────────┐
│ Print [/Program] { "{"format_spec"}" expr_list }                     │
│ ?                                                                    │
└──────────────────────────────────────────────────────────────────────┘

The Print or ?  command evaluates one or more expressions and prints the
results in the Dialogue window, or the application's standard error area
(usually the screen of the task machine) if the /Program qualifier is
specified.  The Print command is useful for examining the values of
variables and expressions.  The expressions can involve registers,
application variables and user-defined debugger variables.  The
operations possible are patterned after those available in the WATCOM C
and WATCOM FORTRAN 77 compilers.  Expressions are fully discussed in the
chapter entitled "VIDEO Expression Handling".

By default, integer values are printed in the current default numeric
radix, pointer values are printed in hexadecimal notation, and
floating-point values are printed in floating-point notation.  In
addition, if the expression is an enumerated type, the name of the
enumeration constant corresponding to the numeric value of the
expression is printed.  If the numeric value does not have a
corresponding enumeration constant, the value is printed in the current
default numeric radix.

To print out the value in some other representation, a format string may
also be specified.  Formally, the format specification is defined as
follows:

   format_spec ::= { char | "%"specifier }
   specifier   ::= "i" | "d" | "u" | "x" | "X"
                       | "o" | "p" | "c" | "s" | "%"
                       | "f" | "g" | "G" | "e" | "E"
                       | "r" | "a" | "l"

Text may be included to annotate the output.

Specifiers: Description:

"i"    The corresponding argument is printed out as a signed decimal
       integer value.

"d"    The corresponding argument is printed out as a signed decimal
       integer value.

"u"    The corresponding argument is printed out as an unsigned decimal
       integer value.

"x"    The corresponding argument is printed out as an unsigned
       hexadecimal integer value.  Letter digits are printed in lower
       case (a-f).

"X"    The corresponding argument is printed out as an unsigned
       hexadecimal integer value.  Letter digits are printed in upper
       case (A-F).

"o"    The corresponding argument is printed out as an unsigned octal
       integer value.

"p"    The corresponding argument is printed out as a pointer
       (segment:offset) value in hexadecimal notation.

"c"    The corresponding argument is printed out as a single character
       value.

"s"    The corresponding argument is printed out as a C string value.
       The argument must point to a string of characters terminated by a
       byte whose value is zero.

"%"    To print out a percentage symbol, the "%" must be doubled up
       (i.e.  %%).

"f"    The corresponding argument is printed out in floating-point
       representation.  If the floating-point value has a very large or
       small magnitude, you should use one of "g", "G", "e" or "E"
       formatting.

"g"    The corresponding argument is printed out in floating-point
       representation.  Numbers of very large or small magnitude are
       printed out in scientific "E" notation (e.g., 1.54352e+16).  The
       exponent letter is printed in lower case.

"G"    The corresponding argument is printed out in floating-point
       representation.  Numbers of very large or small magnitude are
       printed out in scientific "E" notation (e.g., 1.54352E+16).  The
       exponent letter is printed in upper case.

"e"    The corresponding argument is printed out in scientific "E"
       notation (e.g., 1.23456e+02).  The exponent letter is printed in
       lower case.

"E"    The corresponding argument is printed out in scientific "E"
       notation (e.g., 1.23456E+02).  The exponent letter is printed in
       upper case.

"r"    The corresponding argument is printed out in the current default
       numeric radix.

"a"    The corresponding argument is printed out as a symbol reference
       (symbol_name+offset) when possible; otherwise it is printed out
       as a pointer (segment:offset) value in hexadecimal notation.

"l"    The corresponding argument is printed out as a line number
       reference (module_name@line_number+offset) when possible;
       otherwise it is printed out as a pointer (segment:offset) value
       in hexadecimal notation.

Example:
   DBG>print ax
   DBG>? ax

The value of the AX register is displayed in hexadecimal format
(assuming a default numeric radix of 16) in the Dialogue window.

Example:
   DBG>? [dx ax]

The contents of the DX and AX registers are treated as a single 32-bit
long integer and displayed in hexadecimal format (assuming a default
numeric radix of 16).  This grouping of registers is called an
aggregate.

Example:
   DBG>? {%i} [cx bx]

The aggregate formed by concatenating the CX and BX registers is treated
as a 32-bit long integer and displayed in decimal integer format.

Example:
   DBG>? (float) [ax bx]

By employing type casting, the long integer value in this register
aggregate is converted to a floating-point value and displayed in
floating-point format.

Example:
   DBG>? [float] [ax bx]

By employing the type "pun" operator, the 32-bit value in this register
aggregate is treated as a floating-point value and displayed in
floating-point format.  By default, the 32-bit quantity would have been
treated as a long integer.

Example:
   DBG>? [ax bx cx dx]

The aggregate formed from the AX, BX, CX and DX registers is treated as
a 64-bit floating-point entity and displayed in floating-point format.
By default, 64-bit register aggregates are treated as double precision
floating-point values.

Example:
   DBG>print {The answer is %d (0x%x)} ans=foo/2, ans

The result of dividing the value of foo by 2 is displayed in the
Dialogue window in both decimal and hexadecimal format.

Example:
   DBG>? &main_

The address of main_ (segment:offset) is displayed in the Dialogue
window.

Example:
   DBG>? {The address of "main" is %p} &main_

The address of main_ (segment:offset) is displayed as part of a string
of text in the Dialogue window.

Example:
   DBG>? ax=dx

The contents of the DX register are assigned to the AX register and the
result is displayed in the Dialogue window.

Example:
   DBG>print {%c-%c-%c-%c}3,4,5,6

The "heart", "diamond", "club" and "spade" characters are displayed in
the Dialogue window separated by hyphens.

Example:
   DBG>print {%f} flt_val1

The variable flt_val1 is displayed in floating-point notation.

Example:
   DBG>? {%i} (int) 3.1415926

The argument is displayed as the decimal integer value 3.

Example:
   DBG>? (char *) 256

The argument (a pointer) is displayed as a pointer value in hexadecimal
notation (e.g., "0100").  This is the default formatting for pointers.

Example:
   DBG>? {%r} (char *) 256

The argument (a pointer) is displayed in the current default radix
("0256" if the current default radix is decimal).

Consider the following 16-bit example.

Example:
   DBG>? {%x,%x} 65536, (int) 65536

The first argument, the long integer 65536, is displayed as "10000".
The second argument is converted to a short integer and is displayed as
"0" since 65536 exceeds the range of 16-bit unsigned values by 1.


Printing Array Slices
─────────────────────
When the appropriate type information is available, VIDEO can print out
the contents of an array.  By default, the debugger will print out the
contents of the entire array.  Consider the following 3-dimensional
array defined in the C programming language.

Example:
   char *ProcessorType[2][4][2] =
       { { { "Intel 8086",   "Intel 8088"  },
           { "Intel 80186",  "Intel 80188" },
           { "Intel 80286",  "unknown" },
           { "Intel 80386",  "unknown" } },

         { { "NEC V30",      "NEC V20" },
           { "unknown",      "unknown" },
           { "unknown",      "unknown" },
           { "unknown",      "unknown" } } };

This array can be viewed as two layers of rectangular matrices of 4 rows
by 2 columns.  The array elements are all pointers to string values.

To examine the contents of the array, the following command can be
issued.  The response to the command is also shown.

Example:
   DBG>?processortype
   {[0]={[0]={[0]=0x0024, [1]=0x002F},
         [1]={[0]=0x003A, [1]=0x0046},
         [2]={[0]=0x0052, [1]=0x005E},
         [3]={[0]=0x0066, [1]=0x005E}},
    [1]={[0]={[0]=0x0072, [1]= 0x007A},
         [1]={[0]=0x005E, [1]=0x005E},
         [2]={[0]=0x005E, [1]=0x005E},
         [3]={[0]=0x005E, [1]=0x005E}}}

The values shown are the addresses of the string values.

By using dimension specifiers, specific slices of an array can be
displayed.  To see only the values of the first layer, the following
command can be issued.

Example:
   DBG>?processortype[0]
   {[0]={[0]=0x0024, [1]=0x002F},
    [1]={[0]=0x003A, [1]=0x0046},
    [2]={[0]=0x0052, [1]=0x005E},
    [3]={[0]=0x0066, [1]=0x005E}}

Note that this corresponds to the first half of the addresses displayed
in the previous example.

To see only the first row of the first layer, the following command can
be issued.

Example:
   DBG>?processortype[0][0]
   {[0]=0x0024, [1]=0x002F}

To see the second row of the first layer, the following command can be
issued.

Example:
   DBG>?processortype[0][1]
   {[0]=0x003A, [1]=0x0046}

To see the value of a specific entry in a matrix, all the indices can be
specified.

Example:
   DBG>?{%s} processortype[0][0][0]
   Intel 8086
   DBG>?{%s} processortype[0][0][1]
   Intel 8088
   DBG>?{%s} processortype[0][1][0]
   Intel 80186

In the above examples, we use the "%s" format specifier to display the
string values.
::::PRINT_WINDOW
┌──────────────────────────────────────────────────────────────────────┐
│ Print /Window expr                                                   │
│ ?                                                                    │
└──────────────────────────────────────────────────────────────────────┘

The Print /Window command may be used to display the results of a Print
command in a Variable Display window that is created dynamically.

A Variable Display window is placed on the screen showing the variable
including fields if it is a structure.  The window is updated each time
the debugger is entered.  The window may be manipulated in the same
manner as other windows.  When the Variable Display window is created,
it inherits the colour attributes of the Dialogue window.  The Ctrl/P
(paint) key may be used to redefine the window's colour attributes.  It
may be resized using the Ctrl/N (narrow), Ctrl/W (widen), Ctrl/S
(shrink), and Ctrl/G (grow) keys or by manipulating the "resizer" gadget
with a mouse.  It may be moved using the Ctrl/U (up), Ctrl/D (down),
Ctrl/L (left) and Ctrl/R (right) keys or by dragging the title line with
a mouse.  The window may be removed using the Ctrl/E (erase) key or by
clicking on the "close" gadget.

If a structure is displayed, the cursor up and down keys may be used to
move up and down through fields.  To display the contents of a field,
the Enter key can be pressed.  To return to the previous level, the
Backspace key can be pressed.  Entries that represent structures are
displayed by using "{...}" and entries that represent arrays are
displayed by using "(...)" Essentially, the Enter key permits you to
"descend" to nested structures and the Backspace key permits you to
"ascend" to a previous level.

If an entry represents a string, the "S" key can be used to display the
entry as a string.  The Backspace key can be used to return to the
original display format.

The top entry in the window displays the current structure nesting
level.  You can move the cursor to this entry and edit it.  If the entry
represents a field in a structure, you can ascend to the previous level
by removing the trailing field.  By adding new fields, you can descend
to nested levels.

A mouse can be used to select and view fields by clicking on them.  If
you click on the line of dashes in the window, you will ascend to
previous levels.

The Escape key or the mouse can be used to move to the Prompt window.
::::QNX_STARTUP
┌──────────────────────────────────────────────────────────────────────┐
│ wvideo [options] [:sym_file] [//nid] pid                             │
│    or                                                                │
│ wvideo [options] [:sym_file] [//nid] file_spec [cmd_line]            │
└──────────────────────────────────────────────────────────────────────┘

The square brackets [ ] denote items which are optional.

wvideo is the program name for VIDEO.

options is a list of valid VIDEO options, each preceded by a dash ("-").
       Options may be specified in any order.

sym_file is an optional symbolic debugging information file
       specification.  The specification must be preceded by a colon
       (":").  When specifying a symbol file name, a path such as
       "//5/etc/" may be included.  For QNX, the default file suffix of
       the symbol file is ".sym".

       The symbolic information file can be produced by the WATCOM
       Linker wlink or by the WATCOM Strip Utility wstrip.

nid    is an optional network node identification (nid) on which to
       locate or run the process.  If omitted, the process will be
       located or run on the current node.

pid    is a process identification number of a currently executing
       process.  If a process id is given then VIDEO will attempt to
       attach the specified process.  If a "nid" was also given then
       VIDEO will attempt to attach the specified process on the
       specified node.

file_spec is the file name of the file to be loaded into memory.  When
       specifying a file name, a path such as "//5/etc/" may be
       included.  If a path is omitted, VIDEO will first attempt to
       locate the file in the current directory.  If this fails, VIDEO
       will search for the file in each path listed in the PATH
       environment string.

cmd_line is an optional command line which will be passed on to the
       application.

Example 1:
   % wvideo -reg=4 myapp

VIDEO is invoked with 4 register sets and loads the application called
"myapp".

Example 2:
   % wvideo -reg=4 //5 //7/usr/fred/myapp -x test.dat

VIDEO is invoked with 4 register sets and loads the application called
"myapp", located on node 7 of the network, onto node 5 of the network.
The command line "-x test.dat" is passed to "myapp".

Example 3:
   % wvideo //5 0342

VIDEO is invoked to attach a process identified by pid "0342" running on
node 5.

Command Line Options
────────────────────

┌──────────────────────────────────────────────────────────────────────┐
│     -Console=number                                                  │
│     -Dynamic=space                                                   │
│     -NOFpu                                                           │
│     -Invoke=file_spec                                                │
│     -Lines=number                                                    │
│     -NOInvoke                                                        │
│     -NOMouse                                                         │
│     -Registers=number                                                │
│     -REMotefiles                                                     │
│     -NOSymbols                                                       │
│     -TRap=trap_file[;trap_parm]                                      │
└──────────────────────────────────────────────────────────────────────┘

Options may be specified in any order.  Short forms may be specified for
options and are shown above in capital letters.  If "space" is suffixed
with the letter "K" then "space" refers to multiples of 1K bytes (1024
bytes).  If "space" is suffixed with the letter "B" then "space" refers
to the number of bytes.  If no suffix is specified and "space" is a
number less than 1000 then "space" is assumed to refer to multiples of
1K bytes (1024 bytes); otherwise it refers to the number of bytes.

-Console=number specifies the virtual console number to use for debugger
       windows.  By default, VIDEO will use the first "free" virtual
       console.

-Dynamic=number specifies the initial amount of dynamic storage that
       VIDEO is to reserve for items such as windows, user-defined
       symbols, etc.  The default amount that is set aside is 20480
       bytes (20 Kilobytes).  As additional storage is required, VIDEO
       will allocate it.

-NOFpu requests that the debugger ignore the presence of a math
       coprocessor or emulator.  No memory will be allocated by the
       debugger for saving the context of the 80x87 numeric data
       processor.  Use this option if your application will not use the
       math coprocessor and you wish to reduce the amount of memory
       required by the debugger.

-Invoke=file_spec may be used to specify an alternate name for the
       debugger command file which is to be automatically invoked at
       start-up time.  The default file name is "profile.dbg".  See the
       section entitled "Search Order for VIDEO Support Files" for
       information on how command files are located.

-Lines=number may be used to specify the number of display lines that
       VIDEO is to use.  If this option is not specified, the default
       number of output lines is selected.  When an Enhanced Graphics
       Adapter (EGA) is present, 43 lines of output may be requested.
       When an Video Graphics Array (VGA) is present, 50 lines of output
       may be requested.

-NOInvoke specifies that the default debugger command file is not to be
       invoked.

-NOMouse requests that the debugger ignore any attached mouse.

-Registers=number may be used to specify how many register sets to set
       aside for the recording of register contents.  The default number
       of register sets is 2.  See the description of the Register
       command for more information (this command is described under the
       "REGISTER" topic).

-REMotefiles may be used in conjunction with the remote debugging
       capabilities of the debugger.  Remote debugging involves using
       two personal computers that are connected by means other than the
       network.  One, called the "task machine", is used to run the
       application; the other, called the "debugger machine", is used to
       run the debugger.  When REMotefiles is specified, all debugger
       files (except "trap" files) and application source files are
       opened on the task machine rather than the debugger machine (if
       you are doing local debugging, these two machines are actually
       the same).  The "trap" file must be located on the debugger
       machine because it contains the code to open files on the task
       machine.

       Note that the PATH environment variable on the task machine is
       always used in locating executable image files.  When REMotefiles
       is specified, the debugger also attempts to locate VIDEO's
       support files (command files, trap files, etc.) on the task
       machine.

-NOSymbols requests that VIDEO omit all debugging information when
       loading an executable image.  Information regarding global and
       local symbol names, data types, and line numbers is not
       processed.

-TRap=trap_file[;trap_parm] may be specified when debugging an
       application on a remote machine.  You must specify the name of
       one of the "trap" files provided with VIDEO.  For QNX, the
       default file suffix of the trap file is ".trp".  Trap files are
       usually located in the "/etc/wvideo" directory.  See the section
       entitled "Search Order for VIDEO Support Files" for information
       on how trap files are located.

       If trap_parm is specified, it may be necessary to escape the ";"
       depending on the command shell in use.
::::QUIT
┌──────────────────────────────────────────────────────────────────────┐
│ QUIT                                                                 │
└──────────────────────────────────────────────────────────────────────┘

The QUIT command is used to terminate VIDEO and return to the operating
system.  Any application which may have partially executed is also
terminated.
::::REGISTER
┌──────────────────────────────────────────────────────────────────────┐
│ Register [expr]                                                      │
└──────────────────────────────────────────────────────────────────────┘

The Register command is used to select a VIDEO register set.

Whenever VIDEO is entered, it saves the current register values in a
ring of register sets.  The size of this ring is determined at start-up
time with the Registers option (the default is 2, the maximum is 100).
When the expression result is negative, a previous register set is
selected.  When the expression result is positive, a more recent
register set is selected.  When the expression is omitted, the current
register set is selected.

If the Register window is not present on the screen, the register
display is written to the Dialogue window.  A Register window is created
by using the Display Register command.  The top right hand corner of the
Register window will contain a number in square brackets if you are not
at the most recent register set.  This number represents the number of
register sets that are more recent than the one that is currently being
displayed.  When you issue a Go or Trace command, the currently
displayed register set becomes the "current" register values.  This
feature provides the user with a "checkpoint/restart" capability.

Example:
   DBG>register -1

In the above example, we back up to the previous register set.
::::REMARK
┌──────────────────────────────────────────────────────────────────────┐
│ REMark   comment_line                                                │
│ *                                                                    │
└──────────────────────────────────────────────────────────────────────┘

The REMark or * command provides a means for documenting VIDEO command
files.

Example:
   * Count the number of times a routine is executed
     /cnt_<1>=0
   * Remove the break point definition
   * just in case one already exists
     break/clear /<1>
   * Set the new break point
     break/set <1> {/cnt_<1>++; go/keep}
::::SET
┌──────────────────────────────────────────────────────────────────────┐
│ Set                                                                  │
│   Assembly { Lower | Upper | Inside | Outside }                      │
│   Bell     ON | OFf                                                  │
│   Call     [dflt_call] [dflt_parms] [dflt_return]                    │
│   Dclick   expr                                                      │
│   Fpu      Binary | Decimal                                          │
│   Implicit ON | OFf                                                  │
│   INput    window_name                                               │
│   LAnguage lang_name                                                 │
│   Level    Assembly | Mix | Source                                   │
│   MAcro    window_name key_expr [cmd_list]                           │
│   Menu     ON | OFf | Add cmd_list | ACtivate                        │
│   Pfkey    expr (string | "{" string "}")                            │
│   Radix    expr | ("/"radix_spec [expr])                             │
│   SOurce   [/Add] { "{" {char} "*" {char} "}" }                      │
│   SYmbol   [/Add] { [/(Respect|Ignore)] "{" {char} "*" {char} "}" }  │
│   Tab      expr                                                      │
│   Visible  Assembly | Source [top][,[bot][,bias]]                    │
└──────────────────────────────────────────────────────────────────────┘

The Set command is used to establish operational defaults for other
VIDEO commands.


Disassembly Options
───────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Assembly { Lower | Upper | Inside | Outside }                    │
└──────────────────────────────────────────────────────────────────────┘

These options control how assembly instructions and operands are
displayed.  The "lower" option causes opcodes and registers to be
displayed in lowercase.  The "upper" option causes opcodes and registers
to be displayed in uppercase.  The "inside" option causes register
indexing displacements to be shown inside brackets (e.g., [BP-2],
[EBP-2]).  The "outside" option causes register indexing displacements
to be shown outside brackets (e.g., -2[BP], -2[EBP]).


Warning Bell
────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Bell ON | OFf                                                    │
└──────────────────────────────────────────────────────────────────────┘

The warning beep issued by VIDEO may be turned "on" or "off".  A beep is
issued whenever an error message is printed by the debugger.


Default Call
────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Call [dflt_call] [dflt_parms] [dflt_return]                      │
└──────────────────────────────────────────────────────────────────────┘

The default call type (Far, Interrupt or Near) and the default argument
passing mechanism to be used by the VIDEO Call command may be set.

   dflt_call ::= /(Far | Interrupt | Near)
   dflt_parms ::= "(" [ dflt_loc { "," dflt_loc } ] ")"
   dflt_return ::= "/" | print_list
   dflt_loc ::= reg_name | reg_aggregate

In the following example, we define WATCOM's default calling conventions
for the Call command.

Example:
   DBG>set call /far (ax, dx, bx, cx) ax

To change the default calling convention to one in which "near" calls
are used and all parameters are passed on the stack, we could issue the
following command.

Example:
   DBG>set call /near () ax

See the description of the Call command for more information on argument
passing.


Setting Double-click Rate
─────────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Dclick expr                                                      │
└──────────────────────────────────────────────────────────────────────┘

This command sets the maximum amount of time, in milliseconds, that is
allowed between two presses of the mouse button, for the two clicks to
be recognized as a double-click and not two single clicks.  The default
value is 250 milliseconds (1/4 of a second).

Example:
   DBG>set dclick 750

The above example will cause two mouse presses separated by more than
750 milliseconds (3/4 of a second) to be regarded as two separate clicks
rather than a double-click.

The command show set dclick will show the current value.


Format of Numeric Data Processor Display
────────────────────────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Fpu Binary | Decimal                                             │
└──────────────────────────────────────────────────────────────────────┘

The contents of the 80x87 Numeric Data Processor (NDP, math coprocessor)
registers ST(0), ST(1), etc.  can be displayed in hexadecimal (binary)
format or scientific notation (decimal).  The registers and flags of the
math coprocessor are displayed in the FPU window.

The command show set fpu will show the current setting.

Automatic Command File Invocation
─────────────────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Implicit  ON | OFf                                               │
└──────────────────────────────────────────────────────────────────────┘

When "implicit" is "on", VIDEO will treat an unknown command as the name
of a command file and automatically attempt to invoke it.  When
"implicit" is "off", the INvoke command must be used.

Example:
   DBG>set implicit on
   DBG>* invoke "mix" command file
   DBG>mix

Under QNX, it is possible for a conflict to arise when "implicit" is on.
If a path is specified for a command file name, it will be confused with
the short form of the DO command which is "/".

Example:
   DBG>/etc=1
   DBG>/etc/wvideo/mix

The first example assigns the value 1 to the variable etc.  The second
example attempts to run the "mix" command file from the "/etc/wvideo"
directory but a syntactical error results.  To resolve this conflict,
you can use either the INvoke command or the local file specifier prefix
"@l".

Example:
   DBG>invoke /etc/wvideo/mix
   DBG>@l/etc/wvideo/mix

A similar problem arises under DOS or OS/2 when a drive specifier forms
part of the file name.

Example:
   DBG>d:\\watcom\binb\mix
   DBG>invoke d:\\watcom\binb\mix
   DBG>@ld:\\watcom\binb\mix

The first example results in a syntactical error ("d" is interpreted as
the short form of the Display command).  The second and third examples
resolve the problem.

Local and remote file specifier prefixes are described in the chapter
entitled "Remote Debugging".

Current Window
──────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set INput window_name                                                │
└──────────────────────────────────────────────────────────────────────┘

The Set INput command is used to move the text cursor directly to the
specified window.  The valid window names are:

   Assembly
   Command
   Dialogue
   Fpu
   Memory
   Prompt
   Register
   SOurce
   STack
   Thread

The Tab and Shift Tab keys can also be used to move the text cursor to
the following or previous window.  The selected window becomes the
active window.  Keys and the mouse react in the manner described in the
help topics "KEYS" and "MOUSE".


Expression Syntax
─────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set LAnguage lang_name                                               │
└──────────────────────────────────────────────────────────────────────┘

The debugger expression processor can be set to understand the syntax of
certain programming languages.  The operand lang_name represents the
name of an expression syntax or "parse" file.

C      The file "c.prs" describes the ANSI C programming language
       expression syntax supported by VIDEO.

FORTRAN The file "fortran.prs" describes the ANSI FORTRAN 77 programming
       language expression syntax supported by VIDEO.

Under DOS and OS/2, the "prs" files are usually located in the "BINB"
sub-directory of the directory that VIDEO is installed in.  You should

ensure that the "BINB" directory is included in the PATH environment
variable.

Under QNX, the "prs" files are usually located in the "/etc/wvideo"
directory.  The search order for language parsing files is as follows:

   1. the current directory,
   2. the paths listed in the WVIDEO_PATH environment variable,
   3. the path listed in the HOME environment variable, and, finally,
   4. the "/etc/wvideo" directory.

Example:
   DBG>set language fortran

The debugger will load the expression syntax for FORTRAN 77 from the
file "fortran.prs".

The command show set language will show the current setting.


Debugging Level
───────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Level Assembly | Mix | Source                                    │
└──────────────────────────────────────────────────────────────────────┘

The Set Level command is used to set the default debugging level.

Assembly VIDEO will display debugging information at the assembly
       language level.

       Example:
          DBG>set level assembly

Mix    VIDEO will display debugging information at the source language
       level whenever possible, or at the assembly language level when
       no source line information is available.

       Example:
          DBG>set level mix

       This is the default mode of VIDEO.

Source The source language level is similar to the mix language level
       except that modules for which no source line information is
       available are not traced unless explicitly requested.

       Example:
          DBG>set level source


Macro Hot Keys
──────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set MAcro window_name key_expr [cmd_list]                            │
└──────────────────────────────────────────────────────────────────────┘

The Set MAcro command may be used to define "hot" keys for various
windows.  The valid window names are:

   Assembly
   Command
   Dialogue
   Fpu
   Memory
   Register
   SOurce
   STack
   Thread

The value for key_expr must fall within the range 32 (space) to 126
(tilde).  These are the ASCII printable characters.  One or more
debugger commands can be specified for cmd_list.

Example:
   DBG>set macro source 'v' {view}

In the above example, the command view will be invoked if a lowercase
"v" is pressed when the Source window is active (i.e., when the text
cursor is in the Source window).

Example:
   DBG>set macro assembly 'b' {break dbg$code}

In the above example, the command break dbg$code will be invoked if a
lowercase "b" is pressed when the Assembly window is active (i.e., when
the text cursor is in the Assembly window).  A break point will be set
at the currently highlighted line.

Example:
   DBG>set macro source ' ' {trace/source/over}

In the above example, the command trace/source/over will be invoked if
the space bar is pressed when the Source window is active (i.e., when
the text cursor is in the Source window).  A single-shot trace command
will be executed.

┌──────────────────────────────────────────────────────────────────────┐
│ Note:  The Prompt window is the only window where hot keys cannot be │
│ defined since text must be entered in this window.                   │
└──────────────────────────────────────────────────────────────────────┘


Menu Bar
────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Menu ON | OFf | Add cmd_list | ACtivate                          │
└──────────────────────────────────────────────────────────────────────┘

The Set Menu ON and Set menu OFf commands turn the menu bar display "on"
or "off".

The Set Menu Add command permits the creation of command entries in the
"User" pop-down menu.  An entry is a list of one or more VIDEO commands.
Each new entry is labelled with a letter from the alphabet.  An entry
may be selected by pressing Alt/U to engage the "User" pop-down menu and
then Alt/<letter> where <letter> corresponds to the letter beside the
desired entry.  The mouse can also be used to select an entry.  When an
entry is selected, the commands listed in that entry are executed.  Up
to 20 items can be added to the "User" menu.

The Set Menu ACtivate command emulates the action of pressing and
releasing the Alt key.

Example:
   DBG>set pfkey 10 {set menu activate}

In the above example, we bind the Set Menu ACtivate command to
programmable function key 10.

For a description of VIDEO menus, see the "MENUS" topic.

Programmable Function Keys
──────────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Pfkey expr (string | "{" string "}")                             │
└──────────────────────────────────────────────────────────────────────┘

One or more VIDEO commands can be assigned to a programmable function
(PF) key.  Each time that key is pressed, the commands are executed.
You must use "{" and "}" when you have a ";" in the string since VIDEO
uses the semicolon as a command separator.  If the string is omitted
then the current assignment for the specified PF key is removed.  PF
keys are numbered from 1 to 40.

F1-F10 PF keys 1 through 10 are obtained by pressing one of the keys F1
       through F10 (on some keyboards, these may be labeled PF1 through
       PF10).

F11-F20 PF keys 11 through 20 are obtained by pressing both the Shift
       key and one of keys F1 through F10.

F21-F30 PF keys 21 through 30 are obtained by pressing both the Ctrl key
       and one of keys F1 through F10.

F31-F40 PF keys 31 through 40 are obtained by pressing both the Alt key
       and one of keys F1 through F10.

The expression expr is always evaluated with a radix of 10, regardless
of the current default radix for numbers.

Example:
   DBG>set pfkey 1 go/keep

In the above example, function key F1 is defined with a go/keep command.
Each time the F1 key is pressed, VIDEO will execute this command.  This
form of the "go" command keeps any temporary break point that may have
been specified in a previous "go" command.

Example:
   DBG>set pf 1 {go/keep;?ax}

The above example is similar to the previous except that a second
command has been added.  Now, whenever F1 is pressed, two commands will
be executed.  When a break point occurs, the contents of the AX register
are displayed in the Dialogue window.  This example demonstrates the
importance of the braces.

Example:
   DBG>set pf 1 go/keep;?ax

If omitted as shown above, VIDEO will first execute a Set command and
then it will execute a Print (?) command.  This is equivalent to issuing
the two commands on two separate command lines.

Example:
   DBG>set pf 1 go/keep
   DBG>?ax

Example:
   DBG>/k1=-1
   DBG>set pf 1 if ++k1%3==0{<src}{if k1%3==1{<asm}{<mix}}

The user-defined symbol k1 is set to -1 and programmable function key 1
is assigned a command which may be used to cycle through each one of the
"src.dbg", "asm.dbg" and "mix.dbg" command files.

Example:
   DBG>set pf 1

The current assignment to programmable function key 1 is removed.


Default Numeric Radix and Specifiers
────────────────────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Radix expr | ("/"radix_spec [expr])                              │
└──────────────────────────────────────────────────────────────────────┘

This command may be used to define both the default radix of numbers
entered by the user and what character strings are to be interpreted as
radix specifiers.  The expression expr is always evaluated with a radix
of 10, regardless of the current default radix for numbers.


Setting Default Radix
─────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Radix expr                                                       │
└──────────────────────────────────────────────────────────────────────┘

Example:
   DBG>set radix 10
   DBG>set radix 16
   DBG>set radix 8

The above examples illustrate the setting of a default radix for numeric
values input by the user.  In the first example, we set the default
radix to decimal (i.e., base 10); in the second example, to hexadecimal
(i.e., base 16); and in the third example, to octal (i.e., base 8).  The
minimum radix that you may specify is 2 and the maximum is 36.  The
digits that may be used to form numeric values are taken from the set of
digits (0-9) and the letters of the alphabet (A-Z or a-z).

Suppose that the default radix was set to 36.  In terms of decimal
values, 'A' represents the value 10, 'B' represents the value 11, and so
on up to 'Z' which represents the value 35.

In the absence of a radix specifier, only characters which are valid for
the default radix may appear in a numeric value.  For example, if the
default radix is 16 then you cannot use the letters 'G' through 'Z'.

When a numeric constant could legitimately be interpreted as a symbol
name, VIDEO will first try to find a symbol by that name and, if the
search was unsuccessful, it will treat the string as a constant.

Example:
   DBG>/abc=1
   DBG>?abc

In the above example, the user defines a variable called "abc" and
assigns it the value 1.  In the second statement, the debugger is asked
to print the value of "abc".  If the default radix was 16, this could
represent a numeric value (10*16**2 + 11*16 + 12).  However, VIDEO will
first attempt to locate the symbol "abc".  Since this will succeed, the
value displayed in the Dialogue window is 1.  Note that we could quite
easily form a numeric constant by preceding the letters by a '0' digit.

Example:
   DBG>?0abc

Any time a constant begins with one of the digits '0' through '9', VIDEO
will interpret the item as a numeric value.  Thus a symbol name must not
begin with one of the numeric digits (0-9).

Setting A Radix Specifier
─────────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Radix "/"radix_spec [expr]                                       │
└──────────────────────────────────────────────────────────────────────┘

The second feature of the Set Radix command is the ability to define one
or more radix specifiers.

Example:
   DBG>set radix /0x 16

In the above example, the string "0x" is defined to introduce
hexadecimal (base 16) numbers.  Thus 0x12 represents a hexadecimal
constant.

If the expression is omitted then the string is removed from the set of
current defined radix specifiers.

Example:
   DBG>set radix /0x

In the above example, the string "0x" is removed from the set of radix
specifiers.  Now 0x12 is an illegal construct.

Example:
   DBG>set radix /# 10

In the above example, the string "#" is defined to introduce decimal
(base 10) numbers.  Thus #12 represents a decimal constant.

By defining a selection of radix specifiers, we can enter numeric values
in any radix of our choosing and remain independent of the current
default radix.


Source File Search Patterns
───────────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set SOurce [/Add] { {char} "*" {char} }                              │
└──────────────────────────────────────────────────────────────────────┘

This command is used to define patterns to be applied to module names
when VIDEO searches for a corresponding source file.  VIDEO will first
attempt to open the source file by using the file specification used to

compile the file.  We require a mechanism for specifying other
candidates for the source file in the following cases.

   1. A relative path specification was given at compile time and the
      directory from which you are running the program is different from
      the directory from which the file was compiled.
   2. The source file has been moved to a different directory since it
      was compiled.

The following examples use file name specifications from DOS or OS/2.
To construct equivalent QNX examples, the path separator "\" should be
replaced by "/" and all file specifications should be in lowercase
letters.

Suppose the current directory is "\TEST\O" and the source file
("HELLO.C") is contained in the directory "\TEST\C".  Suppose we use the
following command to compile "HELLO.C".

Example:
   C>wcc ..\c\hello -d2

The compiler will place the string "..\C\HELLO.C" in the object file.
Suppose that we move up a level in the directory and link our program.
We then use VIDEO to load and run the program while in the "\TEST"
directory.  The debugger will not be able to locate the source file
since it will use the file specification "..\C\HELLO.C".

Example:
   DBG>set source *.c

In the above example, we specify that VIDEO should also try to locate a
source file by appending ".c" to the module name.  The asterisk is used
as a place holder for the module name.  The module name in the previous
example is "HELLO".  Thus, after unsuccessfully trying to locate
"..\C\HELLO.C", an attempt will be made to locate the file "HELLO.C".
This attempt will also fail.

Example:
   DBG>set source \test\c\*.c

In the above example, we revise the pattern to include the path
specification for the source file.  Now an attempt will be made to
locate the file "\TEST\C\HELLO.C" and this attempt will succeed.

Example:
   DBG>set source *.c \test\c\*.c

In the above example, we add a second pattern to the list of possible
names for the source file.  If VIDEO is unsuccessful at locating the
source file in the current directory as "HELLO.C", it will also try
"\TEST\C\HELLO.C" as a possibility.

To indicate that we wish to add more patterns to the currently defined
pattern set, we can specify the /Add qualifier.  Without this qualifier,
VIDEO will replace the current pattern set with the one that we specify.
The following example is equivalent to the previous one.

Example:
   DBG>set source *.c
   DBG>set source /add \progs\src\*.c

Under QNX, a path specification that begins with a "/" could be
interpreted as a qualifier.

Example:
   DBG>set source /users/fred/*.c

In the above example, the "/users" qualifier is not supported and an
error will result.  To resolve this conflict, the local file specifier
prefix "@l" can be used.

Example:
   DBG>set source @l/users/fred/*.c

Local and remote file specifier prefixes are described in the chapter
entitled "Remote Debugging".


Symbol Name Pattern Matching
────────────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set SYmbol [/Add] {[/(Respect | Ignore)] {char} "*" {char}}          │
└──────────────────────────────────────────────────────────────────────┘

This command is used to control the manner in which VIDEO will look up a
symbol.  By default, symbol names match if they agree in case (both
upper and lower case characters) and in spelling.  This command can be
used to loosen those restrictions.

Language compilers often prefix or suffix a user-defined global symbol
with one or more special characters such as underscores "_" or currency

symbols "$".  Sometimes all the characters in the name are converted
entirely to upper case or lower case.  To simplify the specification of
symbol names, you can define a series of patterns which VIDEO will use
when looking up a symbol.

Example:
   DBG>set symbol *_

The above pattern indicates that an underscore could be suffixed to the
name you specify.  For example, main might actually be spelled main_.
The asterisk is used as a place holder for the user-specified name.

We can specify several patterns.

Example:
   DBG>set symbol *_ _*

In this example, we are stating that possible alternatives for the
spelling of main are main_ and _main.  VIDEO will search for a symbol by
using the specified patterns.  Patterns are processed in the order they
were given.  If no patterns exist, VIDEO will look for an exact match.

Curly braces may be used to delimit a pattern.

Example:
   DBG>set symbol {*_} {_*}

Within braces, space characters are significant.  Therefore, you would
normally not include them except in the rare case where symbol names
could contain space characters.

To indicate that we wish to add more patterns to the currently defined
pattern set, we can specify the /Add qualifier.  Without this qualifier,
VIDEO will replace the current pattern set with the one that we specify.

To indicate whether the case of the name is important in the process of
looking up the name, we can specify one of /Respect or /Ignore in front
of the list of patterns.

Example:
   DBG>set symbol /ignore *_ _*

In the above example, we indicate for each pattern substitution that the
case of the name is not important.  In this case, the user-specified
name main could match many possible spellings such as main_, Main_,
MAIN_, _MaiN, and so on.

In the previous example, we did not include MAIN as a possible match for
the user-specified main.  To include this case, we could issue the
following command:

Example:
   DBG>set symbol /add /ignore *

VIDEO will now also look for an exact spelling with no regard to case.

We could invent more complicated rules for pattern matching based on
case.

Example:
   DBG>set symbol /ignore * *_ _* /respect _*_

In the above example, we indicate for the first three patterns that the
case of the name is not important but that the case must match for the
last pattern.  If the user-specified name is cmain and the actual
spelling is _CMAIN_ then the debugger will not produce a match.
However, if the user specified CMAIN then the debugger would match it
with _CMAIN_.


Setting the Tab Interval
────────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Tab expr                                                         │
└──────────────────────────────────────────────────────────────────────┘

This command controls how the debugger will display text files with
embedded TAB characters.  A TAB character causes the text following it
to start at the next tab stop.  By default, tab stops are set for every
8 columns.  You can alter this default using the Set Tab command.

Example:
   DBG>set tab 4

The above example will set tab stops for every 4 columns.

The command show set tab will show the current value.

Source and Assembly Window Line Context
───────────────────────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ Set Visible Source | Assembly [top][,[bot],[bias]]                   │
└──────────────────────────────────────────────────────────────────────┘

This command controls how the debugger will display source text in the
Source window or assembly code in the Assembly window.  In these two
windows, the debugger can be instructed to leave so many lines above
(top) and below (bot) the current line when scrolling text or assembly
lines.  The debugger can also be instructed to display lines beginning
at some column other than 1 (bias).

Example:
   DBG>set visible source 1,2,9

In the above example, the debugger is instructed to display at least one
line above the current line, to display at least 2 lines below the
current line, and to not display the first 8 columns of source text.  If
the window is too small for the debugger to adhere to these constraints,
it will do the best it can.

The command show set visible will show the current settings for the
Source and Assembly windows.
::::SHOW
┌──────────────────────────────────────────────────────────────────────┐
│ SHow                                                                 │
│     Calls   [expr]                                                   │
│     Display {window_name}                                            │
│     Flip                                                             │
│     Modules [name]                                                   │
│     Paint   {window_name}                                            │
│     Set     {Assembly | Bell | Call | Dclick | Fpu | Implicit |      │
│             INput | LAnguage | Level | MAcro | Menu | Pfkey |        │
│             Radix | SOurce | SYmbol | Tab | Visible}                 │
└──────────────────────────────────────────────────────────────────────┘

The SHow command may be used to display information about the currently
executing application and various VIDEO settings.

Show Calling Sequence
─────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ SHow Calls [expr]                                                    │
└──────────────────────────────────────────────────────────────────────┘

This command is used to display an execution trace-back of the calling
sequence.  In order to display the execution trace-back, local symbol
information is required for all functions in the trace-back.  VIDEO will
list all functions up to the first for which no local symbol information
is available.  For information on generating local symbol information,
see the book entitled "WATCOM Linker User's Guide" ("The DEBUG
Directive").

If an expression is specified, it is evaluated and only that many levels
of the calling sequence are displayed.

In the following example, we show a calling sequence in the C "Calendar"
program.

Example:
   DBG>show calls
   at          PosCursor+32(calendar@160)
   called from Line+68(calendar@147)
   called from Box+39(calendar@121)
   called from Calendar+43(calendar@79)
   called from main+70(calendar@40)

In the following example, we show a calling sequence in the FORTRAN 77
"Calendar" program.

Example:
   DBG>show calls
   at          POSCURSOR+22(calendar@149)
   called from LINE+234(calendar@124)
   called from BOX+65(calendar@101)
   called from CALENDAR+107(calendar@63)
   called from FMAIN+120(calendar@22)
   DBG>log


Show Window Settings
────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ SHow Display {window_name}                                           │
└──────────────────────────────────────────────────────────────────────┘

This command is used to display the settings for all or some windows.
The valid window names are:

   Assembly
   Command
   Dialogue
   Fpu
   Memory
   Prompt
   Register
   SOurce
   STack
   Thread

Example:
   DBG>show display assembly register
   display assembly /open {Assembly: *} 20,24,1,80
   display register /close {CPU} 3,22,72,80

If no window name is specified then the settings for all windows are
displayed.


Show Flip Setting
─────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ SHow Flip                                                            │
└──────────────────────────────────────────────────────────────────────┘

This command is used to show the current setting for screen flipping.
See the description of the Flip command for more information.


Show Module Names
─────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ SHow Modules [name]                                                  │
└──────────────────────────────────────────────────────────────────────┘

This command is used to display the names of modules in the current
application.  If name is specified, only those module names that begin
with "name" are displayed.

Example:
   DBG>show module fp
   FPRTF FPUTC

In the above example, any module names that begin with the letters "fp"
are displayed in the Dialogue window.


Show Window Attributes
──────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ SHow Paint {window_names}                                            │
└──────────────────────────────────────────────────────────────────────┘

This command is used to display the settings of attributes for all or
some windows.  The valid window names are:

   Assembly
   Command
   Dialogue
   Fpu
   Memory
   Prompt
   Register
   SOurce
   STack
   Thread

If no window name is specified then the settings of attributes for all
windows are displayed.  To display a subset, specify only those window
names in which you are interested.

Example:
   DBG>show paint source dialogue
   paint source  plain cyan,black
   paint source  active black,cyan
   paint source  standout brown,black
   paint source  title bright brown,black
   paint source  gadget black,white
   paint dialogue  plain white,black
   paint dialogue  active bright brown,black
   paint dialogue  standout bright magenta,black
   paint dialogue  title bright brown,black
   paint dialogue  gadget black,white

Show Debugger Settings
──────────────────────
┌──────────────────────────────────────────────────────────────────────┐
│ SHow Set {item_names}                                                │
└──────────────────────────────────────────────────────────────────────┘

This command is used to display the current settings of various VIDEO
parameters.  Valid item names are:

   Assembly
   Bell
   Call
   Dclick
   Fpu
   Implicit
   INput
   LAnguage
   Level
   MAcro
   Menu
   Pfkey
   Radix
   SOurce
   SYmbol
   Tab
   Visible

If no argument is specified then all settings are displayed.  To display
a subset, specify only those items in which you are interested.

Example:
   DBG>show set pfkey radix
   set pfkey 1 {help}
   set pfkey 4 {if !?_dbg@pf_4 {/_dbg@pf_4=0};
       if (++_dbg@pf_4)&1 {disp fpu /o} {disp fpu /c}}
   set pfkey 5 {reg -1}
   set pfkey 6 {reg +1}
   set pfkey 7 {/++_dbg@dbg$wind_split;<wind}
   set pfkey 8 {if !?_dbg@pf_8 {/_dbg@pf_8=0};
       if (++_dbg@pf_8)&1 {set menu off;<wind}
       {set menu on;<wind}}
   set pfkey 9 {set input source}
   set pfkey 10 {set input assembly}
   set radix /0n 10
   set radix /0x 16
   set radix /0 8
   set radix 10

In the above example, the current settings of the programmable function
keys and the default radix and radix specifiers are displayed.
::::SUMMARY
BREAK     - set a break point
CALL      - call a routine
DISPLAY   - create and remove VIDEO windows
DO        - assign values to variables, registers, etc.
ERROR     - report an error to the screen
EXAMINE   - examine memory contents
FLIP      - flip to the application's output screen
GO        - resume execution
HELP      - request the interactive help facility
IF        - conditionally execute one or more VIDEO commands
INVOKE    - execute a VIDEO command file
LOG       - log VIDEO output to a file
MODIFY    - modify memory locations
NEW       - reload a task, respecify the command line, or redirect the
            standard input and output files
PAINT     - establish colour attributes for VIDEO windows
PRINT     - display variable contents
QUIT      - quit debugging the application and leave VIDEO
REGISTER  - restore a specific register set
REMARK    - document a VIDEO command file
SET       - establish various VIDEO operating parameters (disassembly
            format, warning bell, "Call" command conventions, mouse double
            click rate, math coprocessor display, command file invocation,
            current window, expression grammar, language level, macro hot
            keys, menu display, programmable function keys, numerical radix,
            source file location and naming patterns, symbol name case
            sensitivity and naming conventions, source file tab expansion
            factor, source and assembly window text display boundaries)
::::SYMBOLS
VIDEO defines a number of symbols which have special meaning.  Each of
the registers is designated by a special name.

eax    32-bit EAX register (32-bit mode only)
ax     16-bit AX register
al     8-bit AL register
ah     8-bit AH register
ebx    32-bit EBX register (32-bit mode only)
bx     16-bit BX register
bl     8-bit BL register
bh     8-bit BH register
ecx    32-bit ECX register (32-bit mode only)
cx     16-bit CX register
cl     8-bit CL register
ch     8-bit CH register
edx    32-bit EDX register (32-bit mode only)
dx     16-bit DX register
dl     8-bit DL register
dh     8-bit DH register
eip    Instruction pointer register (32-bit mode only)
ip     Instruction pointer register
esi    Source index register (32-bit mode only)
si     Source index register
edi    Destination index register (32-bit mode only)
di     Destination index register
esp    Stack pointer register (32-bit mode only)
sp     Stack pointer register
ebp    Base pointer register (32-bit mode only)
bp     Base pointer register
cs     Code segment register
ds     Data segment register
es     Extra segment register
fs     Segment register (32-bit mode only)
gs     Segment register (32-bit mode only)
ss     Stack segment register
fl     Flags register
efl    Flags register (32-bit mode only)
fl.flg_bit_name Individual bits in Flags register

          flg_bit_name ::= "c" | "p" | "a" | "z" | "s" | "i" | "d" | "o"

efl.flg_bit_name Individual bits in Flags register

          flg_bit_name ::= "c" | "p" | "a" | "z" | "s" | "i" | "d" | "o"

       The following table lists the full name for each of the flags
       register bits:

       fl.o, efl.o overflow flag
       fl.d, efl.d direction flag
       fl.i, efl.i interrupt flag
       fl.s, efl.s sign flag
       fl.z, efl.z zero flag
       fl.a, efl.a auxiliary carry flag
       fl.p, efl.p parity flag
       fl.c, efl.c carry flag

st0 - st7 Numeric Data Processor registers (math coprocessor registers)
cw     NDP control word (math coprocessor control word)
cw.cw_bit_name Individual bits in the control word

          cw_bit_name ::= "ic" | "rc" | "pc" | "iem" | "pm" |
                                  "um" | "om" | "zm" | "dm" | "im"

       The following table lists the full name for each of the control
       word bits:

       cw.ic  infinity control

                 0 = projective
                 1 = affine

       cw.rc  rounding control (2 bits)

                 00 = round to nearest or even
                 01 = round down (towards negative infinity)
                 10 = round up (towards positive infinity)
                 11 = chop (truncate toward zero)

       cw.pc  precision control (2 bits)

                 00 = 24 bits
                 01 = reserved
                 10 = 53 bits
                 11 = 64 bits

       cw.iem interrupt enable mask (8087 only)

                 0 = interrupts enabled
                 1 = interrupts disabled (masked)

       cw.pm  precision (inexact result) mask
       cw.um  underflow mask
       cw.om  overflow mask
       cw.zm  zero-divide mask
       cw.dm  denormalized operand mask
       cw.im  invalid operand mask

sw     NDP status word (math coprocessor status word)
sw.sw_bit_name Individual bits in the status word

          sw_bit_name ::=  "b" | "c3" | "st" | "c2" | "c1" |
                                  "c0" | "es" | "sf" | "pe" | "ue" |
                                  "oe" | "ze" | "de" | "ie"

       The following table lists the full name for each of the status
       word bits:

       sw.b   busy
       sw.c3  condition code bit 3
       sw.st  stack stop pointer (3 bits)

                 000 = register 0 is stack top
                 001 = register 1 is stack top
                 010 = register 2 is stack top
                     .
                     .
                     .
                 111 = register 7 is stack top

       sw.c2  condition code bit 2
       sw.c1  condition code bit 1
       sw.c0  condition code bit 0
       sw.es  error summary (287, 387 only)
       sw.sf  stack fault (387 only)
       sw.pe  precision (inexact result) exception
       sw.ue  underflow exception
       sw.oe  overflow exception
       sw.ze  zero-divide exception
       sw.de  denormalized operand exception
       sw.ie  invalid operation exception

VIDEO permits the manipulation of register contents using any of the
operators described under the topics "C_OPERATORS" and "F77_OPERATORS".
By default, these predefined names are accessed just like any other
variables defined by the user or the application.  Should the situation
ever arise where the application defines a variable whose name
conflicts with that of one of these debugger variables, the module
specifier _dbg may be used to resolve the ambiguity.  For example, if
the application defines a variable called cs then _dbg@cs can be
specified to resolve the ambiguity.  The "_dbg@" prefix indicates that
we are referring to a VIDEO defined symbol rather than an application
defined symbol.

The flags register, the NDP control word, and the NDP status word can be
accessed as a whole or by its component status bits.

Example:
   /fl.c=0
   /cw.um=0
   ?sw.oe

In the above example, the "carry" flag is cleared, the NDP underflow
mask of the control word is cleared, and the NDP overflow exception bit
of the status word is printed.

The low order bit of the expression result is used to set or clear the
specified flag.

Example:
   fl.c=0x03a6

In the above example, the "carry" flag is cleared since the low order
bit of the result is 0.

VIDEO also defines some other special names.

dbg$32 This debugger symbol represents the mode in which the processor
       is running.

       0      16-bit mode
       1      32-bit mode

dbg$bottom This debugger symbol represents the number of the last line
       on the screen which may be used for windows (see also dbg$top,
       dbg$left, dbg$right).

dbg$bp This debugger symbol represents the register pair SS:BP (16-bit
       mode) or SS:EBP (32-bit mode).

       Example:
          ? dbg$bp

dbg$code This debugger symbol represents the current code location under
       examination.  The dot address "." is either set to dbg$code or
       dbg$data, depending on whether you were last looking at code or
       data.

dbg$cpu This debugger symbol represents the type of central processing
       unit which is in your personal computer system.

       0      Intel 8088, 8086 or compatible processor
       1      Intel 80188, 80186 or compatible processor
       2      Intel 80286 or compatible processor
       3      Intel 80386 or compatible processor
       4      Intel 80486 or compatible processor

dbg$ctid This debugger symbol represents the identification number of
       the current execution thread.  Under DOS, the current thread ID
       is always 1.  The current execution thread can be selected using
       the Thread window or the Thread command.

dbg$data This debugger symbol represents the current data location under
       examination.  The dot address "." is either set to dbg$code or
       dbg$data, depending on whether you were last looking at code or
       data.

dbg$etid This debugger symbol represents the identification number of
       the thread that was executing when the debugger was entered.
       Under DOS, the executing thread ID is always 1.

dbg$fpu This debugger symbol represents the type of numeric data
       processor (math coprocessor) that is installed in your personal
       computer system.

       -1     An 80x87 emulator is installed
       0      No coprocessor is installed
       1      An Intel 8087 is installed
       2      An Intel 80287 is installed
       3      An Intel 80387 is installed
       4      An Intel 80486 processor, supporting coprocessor
              instructions, is installed

dbg$ip This debugger symbol represents the register pair CS:IP (16-bit
       mode) or CS:EIP (32-bit mode).

       Example:
          ? dbg$ip

dbg$left This debugger symbol represents the number of the first column
       on the screen which may be used for windows (see also dbg$right,
       dbg$top, dbg$bottom).

dbg$monitor This debugger symbol represents the type of monitor adapter
       which is in use.

       0      IBM Monochrome Adapter
       1      IBM Colour Graphics Adapter (CGA)
       2      IBM Enhanced Graphics Adapter (EGA)
       3      IBM Video Graphics Array (VGA)

dbg$os This debugger symbol represents the operating system that is
       currently running the application.

       1      DOS
       2      OS/2
       3      386|DOS-Extender from Phar Lap Software, Inc.
       4      OS/386 from ERGO Computing, Inc.
       5      NetWare 386 from Novell, Inc.
       6      QNX from Quantum Software Systems Ltd.
       7      DOS/4GW from Rational Systems, Inc.
       8      Microsoft Windows

dbg$pid (OS/2, NetWare 386, QNX only) This debugger symbol contains the
       process identification value for the program being debugged.

dbg$psp (DOS only) This debugger symbol contains the segment value for
       the DOS "program segment prefix" of the program being debugged.

dbg$radix This debugger symbol represents the current default numeric
       radix.

dbg$remote This debugger symbol is 1 if the "REMotefiles" option was
       specified and 0 otherwise.

dbg$right This debugger symbol represents the number of the last column
       on the screen which may be used for windows (see also dbg$left,
       dbg$top, dbg$bottom).

dbg$sp This debugger symbol represents the register pair SS:SP (16-bit
       mode) or SS:ESP (32-bit mode).

       Example:
          ? dbg$sp

dbg$top This debugger symbol represents the number of the first line on
       the screen which may be used for windows (see also dbg$left,
       dbg$right, dbg$bottom).

dbg$view This debugger symbol is set by the View command.  It represents
       the segment and offset of the code corresponding to the line
       where the cursor was last positioned when viewing a module of the
       current application.  This variable has several uses.  For
       example, it can be used in a Break command to set a break point.

       Example:
          break dbg$view
::::SYSTEM
┌──────────────────────────────────────────────────────────────────────┐
│ SYstem[/(Remote | Local)] [ system_cmd | "{" system_cmd "}" ]        │
│ !                                                                    │
└──────────────────────────────────────────────────────────────────────┘

The SYstem or !  command may be used to run other commands or programs
without destroying the debugging environment.  If system_cmd is entered,
that command is executed by the operating system and control returns to
VIDEO.

If system_cmd is omitted, the operating system command interpreter or
shell is invoked.  Commands may be entered until an "exit" command is
entered.  The shell is terminated and control returns to the debugger.

The /Remote and /Local qualifiers may be specified when using the remote
debugging feature.  If the /Remote qualifier is specified, the command
is run on the task machine.  If the /Local qualifier is specified, the
command is run on the debugger machine.  If neither qualifier is
specified then "local" is assumed unless the Remotefiles option was
specified on the command line.  For more information on remote
debugging, see the chapter entitled "Remote Debugging".

Under QNX, a path specification that begins with a "/" could be
interpreted as a qualifier.

Example:
   DBG>system /users/fred/myapp

In the above example, the "/users" qualifier is not supported and an
error will result.  To resolve this conflict, the /Local qualifier must
be used.

Example:
   DBG>system/local /users/fred/myapp

┌──────────────────────────────────────────────────────────────────────┐
│ Note:  There must be enough unused memory in the computer to run the │
│ specified program or shell.  Under DOS, the program being debugged   │
│ must have released some memory back to the system so that there is   │
│ room to load system_cmd.  For DOS, you can use the "RESIZE" command  │
│ file to set the size of the memory control block containing the      │
│ Program Segment Prefix (PSP) of the program being debugged.  See the │
│ topic "COMMAND_FILES" for more information on this command file.     │
│                                                                      │
│ You can also use the VIDEO "Checksize" option.  See the topic        │
│ "DOS_STARTUP" for more information on this option.                   │
└──────────────────────────────────────────────────────────────────────┘

Example:
   DBG>system c:\cmds\cset.com

In the above DOS example, the program "CSET.COM" is invoked from the "C"
disk and directory "\CMDS".

Example:
   DBG>system

The command shell is invoked.  The shell will not return to the debugger
until an "exit" command is executed.

Example:
   DBG>sys chdir \asmsrc

For DOS only, the shell is invoked to change the current directory to
"\ASMSRC".  Control is then immediately returned to VIDEO.

Example:
   DBG>! edit hello.c

An editor is invoked to edit the file "hello.c".  Corrections to the C
source code could be applied while the "HELLO" program is being
debugged.  When the editor exits, control is returned to VIDEO.

Example:
   DBG>! edit fftc.for

An editor is invoked to edit the file "fftc.for".  Corrections to the
FORTRAN source code could be applied while the "FFTC" program is being
debugged.  When the editor exits, control is returned to VIDEO.
::::THREAD
┌──────────────────────────────────────────────────────────────────────┐
│ THread                                                               │
│ ~                                                                    │
│         /Change   [id_num]                                           │
│         /Freeze   [id_num] | ["*"]                                   │
│         /Show     [id_num] | ["*"]                                   │
│         /Thaw     [id_num] | ["*"]                                   │
└──────────────────────────────────────────────────────────────────────┘

The THread or ~ command is used to manipulate the threads of execution
of a multi-threaded application under OS/2 or NetWare 386.  An execution
thread may be selected for examination by VIDEO (/Change), an execution
thread may be made not runnable (/Freeze), an execution thread may be
made runnable (/Thaw), or the status of execution threads may be
displayed (/Show).

In an application that has multiple threads of execution, a particular
thread may be selected for examination by specifying its thread
identification number or thread ID using the Change option.

Example:
   001>thread/change 2

In the above example, execution thread "2" is selected using the Change
option.  The debugger prompt will change to "002" if an execution
thread, whose ID is "2", exists.  Other windows on the screen will
change to reflect the selection of another execution thread.  In
particular, any Assembly, Source, FPU, and Register windows that are
present on the screen will change.

The Change option need not be specified since it is the default when
only a thread ID is specified.

Example:
   001>thread 2

In the above example, execution thread "2" is selected.

A particular thread may be "frozen" (i.e., made not runnable) by
specifying its thread ID using the Freeze option.

Example:
   002>thread/freeze 3

In the above example, execution thread "3" is made not runnable.

All threads may be frozen by specifying "*" for the thread ID.

Example:
   002>~/f *

The current thread may be frozen by omitting the thread ID.

Example:
   002>thread/freeze

A particular thread may be "thawed" (i.e., made runnable) by specifying
its thread ID using the Thaw option.

Example:
   002>thread/thaw 3

In the above example, execution thread "3" is made runnable.

All threads may be thawed by specifying "*" for the thread ID.

Example:
   002>thread/thaw *

The current thread may be thawed by omitting the thread ID.

Example:
   002>~/th

The status of a particular thread may be displayed by specifying its
thread ID using the Show option.

Example:
   002>thread/show 1

In the above example, the status of execution thread "1" is displayed.

The status of all threads may be displayed by specifying "*" for the
thread ID.

Example:
   002>th/sh *

Alternately, the status of all threads may be displayed by specifying
the Thread command without any arguments.

Example:
   002>thread

The status of the current thread may be displayed by specifying Show and
omitting the thread ID.

Example:
   002>~/s
::::TRACE
┌──────────────────────────────────────────────────────────────────────┐
│ Trace                                                                │
│     [/Assembly] [/Over | /Into | /Next] [start_addr_expr]            │
│     [/Mix]      [/Over | /Into | /Next] [start_addr_expr]            │
│     [/Source]   [/Over | /Into | /Next] [start_addr_expr]            │
└──────────────────────────────────────────────────────────────────────┘

The Trace command is used to step through the execution of a program.
Execution may be viewed one source line at a time (/Source), one
assembly instruction at a time (/Assembly), or a combination of both
source and assembly lines (/Mix).  The latter mode will display source
lines when they are available and switch to assembly instructions when
source line information is not available.

Source line numbers are displayed in the Source window when source line
information is included in the executable image (for additional
information, see the description of the compiler's "d1" option and the
WATCOM Linker "DEBUG" directive).  If the source file can be accessed
then the corresponding source text is also displayed.  For a discussion
of how VIDEO locates the source files that correspond to the modules in
your application, see the description of the Set Source command.
Assembly instructions are displayed in the Assembly window.

When source line information is available, both the Source and Assembly
windows are synchronized.

/Assembly [/Over | /Into | /Next] [start_addr_expr]
       VIDEO will trace execution of the application one assembly
       instruction at a time.

       Example:
          DBG>trace /assembly

/Mix [/Over | /Into | /Next] [start_addr_expr]
       VIDEO will trace execution of the application one source
       statement at a time, or one instruction at a time when no source
       text is available.

       Example:
          DBG>trace /mix

/Source [/Over | /Into | /Next] [start_addr_expr]
       VIDEO will trace execution of the application one source
       statement at a time.  Source line information must be available
       at the time that this command is issued.

       Example:
          DBG>trace /source

When none of the /Assembly, /Mix or /Source qualifiers is specified,
VIDEO will use a default trace mode.  Initially, the default is /Mix but
this default can be set with Set Level command.

By default, VIDEO will enter a tracing mode in which one source
statement or assembly instruction is executed each time one of the SPACE
bar or "I" or "N" keys is pressed.

If the SPACE bar is used to advance execution, the tracing of called
routines is skipped.  Tracing continues with the statement or
instruction following the routine invocation.

Example:
   C Programming Example
          8 int main()
          9   {
         10      printf( "Hello world\n" );
         11      return( 0 );
         12   }

   FORTRAN Programming Example
          8       PROGRAM DEMO
          9       EXTERNAL PRINTF
         10       CALL PRINTF( 'Hello world' )
         11       END

In the above example, we skip the trace of the execution of the "printf"
routine by pressing the SPACE bar when the "printf" statement is about
to be executed.

If the "I" or "into" key is used to advance execution, the execution of
called routines is traced.

Example:
   main_         mov    AX,0002
   main_+03      push   AX
   main_+04      call   printf
   main_+07      add    SP,2
   main_+0A      xor    AX,AX

In the above example, we can trace the execution of the "printf" routine
by pressing the "I" key when the "call" instruction at "main_+04" is
about to be executed.

The "N" or "next" key may be used to advance tracing to the next
sequential statement or instruction immediately following the current
statement or instruction.  In situations where you are at the bottom of
a loop, this permits you to skip over the tracing of statements or
instructions which might be repeated many times.

Example:
   _CSTART_+66   sub    SI,SI
   _CSTART_+68   cmp    BYTE PTR [SI],00
   _CSTART_+6B   movsb
   _CSTART_+6C  *jne    _CSTART_+68
   _CSTART_+6E   cmp    BYTE PTR [SI],00

In the above example, we can skip tracing of the loop from "_CSTART_+68"
to "_CSTART_+6C" by pressing the "N" key when the "jne" instruction at
"_CSTART_+6C" is about to be executed.  The "*" preceding the "jne"
indicates that the branch to "_CSTART_+68" will be taken.  The next
instruction to be traced will be the "cmp" at "_CSTART_+6E".

When using the "N" key, care must be taken to ensure that the execution
path will eventually reach the next statement or instruction.  If
execution fails to reach this point then the program may continue to
execute until completion.  This situation is akin to setting a break
point at a statement or assembly instruction which will never be
executed and then issuing a Go command.  In this situation, the
application would execute to completion.

Tracing can be discontinued by pressing any other key.

The /Over, /Into and /Next modifiers may be used to continue execution
to the "next" statement or instruction after which VIDEO will prompt for
another command.  This is often referred to as "single-step" mode.

/Over  This qualifier may be used to continue execution to the "next"
       statement or assembly instruction.  If the current statement or
       instruction invokes a routine then the "next" statement or
       instruction is the one which follows the invocation of the
       routine.

/Into  This qualifier may be used to continue execution to the "next"
       statement or assembly instruction.  If the current statement or
       instruction invokes a routine then the "next" statement or
       instruction is the first one in the called routine.

/Next  This qualifier may be used to continue execution to the "next"
       statement or assembly instruction which immediately follows the
       current statement or instruction in memory.  If the current
       statement or instruction is one that branches, care must be taken
       to ensure that the execution path will eventually reach the
       statement or instruction which follows.  If execution fails to
       reach this point then the program may continue to execute until
       completion.
::::VIEW
┌──────────────────────────────────────────────────────────────────────┐
│ View[/Binary]  [module_or_file_spec]                                 │
└──────────────────────────────────────────────────────────────────────┘

The View command invokes a simple file browser (i.e., you cannot make
changes to the file, only look at it).  If module_or_file_spec is not
specified then the current module name is assumed.

The argument module_or_file_spec is treated first as a possible module
name and then as a file name.  The debugger attempts to locate the
source file that corresponds to the module in the same manner as that
used when displaying source lines in the Source window.  VIDEO searches
for the file in the devices and paths that you specify in the Set Source
command.

In cases where there is a conflict between a module name and a file
name, a drive (DOS, OS/2), path or file extension can be specified to
resolve the ambiguity.  For example, suppose that you had a data file
called "printf".  If you entered the command view printf then VIDEO
would attempt to locate the file "printf.c".  On the other hand, if you
entered the command view printf.  then VIDEO would attempt to locate the
file "printf".

If /Binary is specified then the file contents are displayed in
hexadecimal notation.  A file name must be specified when this qualifier
is used.

The manipulation of the View window with keys and a mouse is described
under the topics "KEYS" and "MOUSE".

Under QNX, a path specification that begins with a "/" could be
interpreted as a qualifier.

Example:
   DBG>view /users/fred/test.dat

In the above example, the "/users" qualifier is not supported and an
error will result.  To resolve this conflict, the local file specifier
prefix "@l" can be used.

Example:
   DBG>view @l/users/fred/test.dat

Local and remote file specifier prefixes are described in the chapter
entitled "Remote Debugging".
::::WATCH
┌──────────────────────────────────────────────────────────────────────┐
│ Watch                                                                │
│     [/Set]       addr_expr [ cmd_list ]                              │
│     /Byte        addr_expr [ cmd_list ]                              │
│     /Word        addr_expr [ cmd_list ]                              │
│     /DWord       addr_expr [ cmd_list ]                              │
│     /Activate    "*" | index_expr | "/" addr_expr                    │
│     /Deactivate  "*" | index_expr | "/" addr_expr                    │
│     /Clear       "*" | index_expr | "/" addr_expr                    │
└──────────────────────────────────────────────────────────────────────┘

A watch point defines a memory location which, if modified, causes
execution of the application to suspend.  A watch point may be defined
for:

/Byte  a byte (8 bits)

/Word  a word (16 bits), and

/DWord a doubleword (32 bits)

/Set is implied when no other qualifier is specified.  If /Set or no
qualifier is specified, a watchpoint is set for a word or doubleword
depending on whether you are debugging a 16-bit or 32-bit application.
A watchpoint may be removed with the /Clear qualifier.  Watchpoints may
be enabled with the /Activate qualifier or disabled with the /Deactivate
qualifier.  Up to 7 watch points may be defined.  When an instruction
modifies a location guarded by an active watch point, application
execution is suspended and the debugger is entered.

Example:
   DBG>watch/set _listhead
   DBG>watch _listhead

In the above example, two equivalent commands are shown.  A watch point
is defined and automatically activated for the 16-bit memory location
defined by the global symbol _listhead.  Only one watch point may be
specified for a particular location in memory.

When the executing application modifies a memory location guarded by an
active watch point, application execution is suspended and the debugger
is entered.  If one or more debugger commands were specified when the
watch point was defined, the debugger commands are executed first.  The
command list that follows the address expression in the /Set, /Byte,
/Word, or /DWord qualifiers is defined as follows:

   cmd_list ::= "{" [cmd] { ";" [cmd] } "}"

This is simply a VIDEO command line placed inside of braces.

Notes:

   1. Execution of the application may be resumed if one of the commands
      was a Go command; otherwise the debugger prompts the user for a
      new command.

      Example:
         DBG>watch _listhead {if _listhead != 0 {go/keep}}

      Each time the "listhead" variable is modified, its value is
      compared with zero and execution is resumed only if the value is
      not zero.

   2. If no arguments are specified to the "Watch" command, the
      currently defined watch points will be displayed.  The first one
      shown is watch point number 1, the second one shown is watch point
      number 2, and so on.  These are called the watch point indices.
      Active watch points are shown in "active" attributes, inactive
      ones are shown in "plain" attributes.  See the description of the
      Paint command for a discussion of attributes.

   3. When activating, deactivating or clearing a watch point, either
      the watch point index or the address must be specified.  If "*" is
      specified as the watch point index then all watch points are
      affected.

      Example:
         DBG>watch/set _listhead; watch/deac 1
         DBG>watch/set _listhead; watch/deac /_listhead

      In both examples, a watch point is set and then a watch point is
      deactivated.  In the first example, the watch point set for
      _listhead is deactivated only if no other watch points have been
      set (since it will then be watch point number 1).  The second
      example illustrates how the watch point for _listhead will be
      deactivated under any circumstances.

      Example:
         DBG>watch/activate 2; watch/deactivate 1

      Watch point number 2 is activated and 1 is deactivated.

   4. The specified address need not be the name of a symbol.

      Example:
         DBG>watch/byte es:di

      A watch point is set for the 8-bit location specified by the
      contents of the ES:DI register pair.

      Example:
         DBG>watch/deactivate /bx

      The watch point whose address is specified by the contents of the
      DS:BX register pair is deactivated.

   5. All watch points may be removed in a single command.

      Example:
         DBG>watch/clear *

      The asterisk refers to all watch points.
::::WHILE
┌──────────────────────────────────────────────────────────────────────┐
│ WHile <expr> cmd_list                                                │
└──────────────────────────────────────────────────────────────────────┘

The WHile command permits execution of a list of commands while the
specified expression is true (i.e., evaluates to a non-zero result).
The command list that follows the command is defined as follows:

   cmd_list ::= "{" [cmd] { ";" [cmd] } "}"

Example:
   DBG>/ax=0; while ax!=25 {/ax++;print ax}

The above example prints the numbers from 1 to 25 in the Dialogue
window.  It first sets the AX register to 0.  While the content of the
AX register is not equal to 25, the debugger will increment the value in
the AX register and print the new value.

There are more complex scenarios in which the WHile command can be put
to good use.  For example, it could be used to follow a linked list
which is terminated by a NULL pointer.
::::WINDOWS
VIDEO Windows
─────────────

Windows are rectangular areas on the screen which are devoted to
displaying a particular type of debugging information such as source
lines, machine language instructions, and register contents.  Not all
windows need be present on the screen.  Windows are placed on the screen
with the VIDEO Display command.  The same command can be used to remove
windows from the screen.  The attributes of lines displayed in a window
are defined with the VIDEO Paint command.

Action Window
─────────────

The debugger places this window on the screen after a text selection
sequence has been engaged and completed.  Using the keyboard, text
selection is engaged using the Ctrl/Enter key.  When the Ctrl/Enter key
is pressed a second time, the Action window appears on the screen.

Using the mouse, text selection is engaged when the right-hand mouse
button is pressed.  When the right-hand mouse button is released, the
Action window appears on the screen.

The entries in the Action window allow you to

   1. show the source code pertaining to the selected text,

   2. display the contents of the variable represented by the selected
      text,

   3. evaluate the selected text as an expression,

   4. examine the memory location represented by the selected text,

   5. set a break point at the location represented by the selected
      text,

   6. set a watch point on the location represented by the selected
      text,

   7. or copy the selected text to the Prompt window where it can be
      manipulated as part of some command.

The use of keys and mouse in the text selection process is described
later on in the sections entitled "Window Manipulation with Keys" and
"Using a Mouse with VIDEO".


Assembly Window
───────────────

The debugger displays assembly instructions for the current code
location in this window.  If the Code Segment and Instruction Pointer
registers (CS:IP, CS:EIP) point to an instruction visible in the
Assembly window then the line containing that instruction is displayed
in "active" attributes.  When examining assembly instructions, one line
is designated as the current line and is displayed in "standout"
attributes.  The Source window, if present, is kept synchronized with
the Assembly window provided that source information is available.

Command Window
──────────────

The debugger will display output from one or more commands that can be
bound to this window.  In the illustration above, the sample command
window is titled "date/time structure".


Dialogue Window
───────────────

By default, the debugger displays responses to commands in this window.
When one of the other windows is not present on the screen, the output
normally destined for that window is displayed in the Dialogue window.


FPU Window
──────────

The contents of the 80x87 numeric data processor (math coprocessor)
registers and status flags are displayed in this window.  When the FPU
window is active, the currently selected item is displayed in "active"
attributes.  When the contents of a register have changed from the last
time that the debugger was entered, it is displayed in "standout"
attributes.

Memory Window
─────────────

A portion of memory is displayed in this window.  When the Memory window
is active, the currently selected memory location is displayed in
"active" attributes.  Memory window "hot spots" (e.g., BYTE ) are
displayed in "standout" attributes.  All other items are displayed in
"plain" attributes.


Prompt Window
─────────────

The debugger command input prompt "DBG>" is displayed in a window that
is one line high.  The prompt window is used to enter command lines.

In multiple execution thread applications, the "DBG>" prompt is replaced
by a prompt that indicates the current thread.  The form of the prompt
is "ddd>" where "ddd" is the thread identification number.

Example:
   002>


Register Window
───────────────

In 16-bit mode, the current contents of the 8086 registers are displayed
in the Register window.

In 32-bit mode, the current contents of the 32-bit registers are
displayed in the Register window.

When the Register window is active, the currently selected item is
displayed in "active" attributes.  When the contents of a register have
changed from the last time that the debugger was entered, it is
displayed in "standout" attributes.  An exception to this rule is the
Instruction Pointer (IP, EIP) register which is only displayed in
"standout" attributes when its value changes because some type of branch
or call instruction was executed.

If a register set other than register set 0 is displayed, then the
register set number is displayed in brackets (e.g., [1]) with "active"
attributes (see the description of the Register command).

Source Window
─────────────

If program source code information is available for the current code
location then it will be displayed in this window.  If the Code Segment
and Instruction Pointer registers (CS:IP, CS:EIP) point to a source line
visible in the Source window then the line is displayed in "active"
attributes.  When examining source code, one line is designated as the
current line and is displayed in "standout" attributes.  The Assembly
window, if present, is kept synchronized with the Source window.

Stack Window
────────────

A portion of the execution stack is displayed in this window.  If the
Base Pointer (BP, EBP) register points to a visible byte, word or
doubleword on the stack, that item is displayed in "standout"
attributes.  When the Stack window is active, the currently selected
stack location is displayed in "active" attributes.  All other items are
displayed in "plain" attributes.

Thread Window
─────────────

The Thread window is used to display the identification number, state
and name of all program execution threads.  Whenever the debugger is
entered, the currently executing thread is displayed in "active"
attributes.  When a new thread entry has been selected, it is displayed
in "active" attributes.

Each entry in the Thread window has 3 fields.  The first field is the
thread identification number or thread ID.  The second field is the
thread state which may be one of "runnable" or "frozen".  The third
field is the thread name which is applicable to NetWare 386 server tasks
only.  The currently selected field is displayed in "standout"
attributes.  All other items are displayed in "plain" attributes.

Under DOS and QNX, there is only one execution thread so there is only
one entry in the Thread window.  Under OS/2 and NetWare 386, there may
be several execution threads so there may be be several entries in the
Thread window.

Variable Window
───────────────

This window is created by the Print /Window command.  The debugger will
display output from a Print command in this window.  The window is
updated each time the debugger is entered or a VIDEO command is
executed.  In the illustration above, the sample Variable window is
titled "Variable Display".


View Window
───────────

This window is created by the Help and View commands.  The View window
occupies the entire display area when it is active.  When the command
completes, the View window is removed and other windows are redisplayed.


Error Window
────────────

In addition to the windows described in earlier sections, an "error"
window may appear in the middle of the screen when VIDEO wishes to issue
an error message.  This window will disappear when any key is pressed.
::::~~~DEFAULT
      ┌──────────────────────────────────────────────────────────┐
      │                      W V I D E O                         │
      │  WATCOM Visual Interactive Debugging Execution Overseer  │
      └──────────────────────────────────────────────────────────┘

   Help is available on the following topics.  To obtain help on a
   particular topic, enter a command of the following form:

        HELP topic

    <BREAK>          <CALL>           <COMMAND_FILES>  <C_OPERATORS>
    <DISPLAY>        <DO>             <DOS_EXTENDER>   <DOS_STARTUP>
    <ERROR>          <EXAMINE>        <F77_OPERATORS>  <FLIP>
    <GO>             <HELP>           <IF>             <INVOKE>
    <KEYS>           <LOG>            <MENUS>          <MODIFY>
    <MOUSE>          <NEW>            <NOTATION>       <OS2_STARTUP>
    <PAINT>          <PRINT>          <PRINT_WINDOW>   <QNX_STARTUP>
    <QUIT>           <REGISTER>       <REMARK>         <SET>
    <SHOW>           <SUMMARY>        <SYMBOLS>        <SYSTEM>
    <THREAD>         <TRACE>          <VIEW>           <WATCH>
    <WHILE>          <WINDOWS>

   Short forms for the topic name may be specified.