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    Write command

    Purpose:  Writes the data being debugged to disk.

                                              
                 Use this command with care   
                                              

    Format:   W [address [drive sector sector]]

    Remarks:  The maximum number of sectors that can be written with a
              single Write command is 80h (128).

              DEBUG displays a message if a disk write error occurs. You
              can retry the write operation by pressing F3 to redisplay
              the Write command, then press the Enter key.

              The Write command has two format options:

              Option 1                                                    

              Use this option to write data to disk beginning at a speci-
              fied address. For example:

              W address drive sector sector

              The data beginning at the specified address is written to
              the disk in the indicated drive. The data is written start-
              ing at the specified starting relative sector (first sector)
              and continues until the requested number of sectors are fil-
              led (second sector).

              Notes:

              1.  Be extremely careful when you write data to absolute
                  sectors because an erroneous sector specification destroys
                  whatever was on the disk at that location.

              2.  If only an offset is entered for the beginning address,
                  the W command assumes the segment contained in the CS
                  register.

              3.  Remember, the starting sector and the sector count are
                  both specified in hexadecimal.

              4.  Option 1 cannot be used if the drive specified is a net-
                  work drive.

              For example:

              W 1FD 1 100 A

              The data beginning at CS:01FDh is written to the disk in
              drive B, starting at relative sector 100h (256) and conti-
              nuing for 0Ah (10) sectors.


              Option 2                                                    

              This option allows you to use the Write command without spe-
              cifying parameters or only specifying the address parameter.
              For example:

              W
                 or
              W address

              When issued as shown above, the Write command writes the file
              (whose filespec is at CS:80h) to disk.

              This condition is met by specifying the filespec when start-
              ing the DEBUG program, or by using the Name command.

              Note:
              If DEBUG was started with a filespec and subsequent Name
              commands were used, you may need to enter a new Name command
              for the proper filespec before issuing the Write command.

              In addition, the BX and CX registers must be set to the
              number of bytes to be written. They may have been set pro-
              perly by the DEBUG or Load commands, but might have been
              changed by a Go or Trace command. You must be certain the
              BX and CX registers contain the correct values.

              The file beginning at CS:100h, or at the location specified
              by address, is written to the disk in the drive specified in
              filespec or the default drive if none was specified.

              The debugged file is written over the original file that was
              loaded into memory, or into a new file if the filename in the
              FCB didn't previously exist.

              Note:
              An error message is issued if you try to write a file with
              an extension of .EXE or .HEX. These files must be written
              in a specific format that DEBUG cannot support.

              If you find it necessary to modify a file with an extension
              of .EXE or .HEX, and the exact locations to be modified are
              known, use the following procedure:

              1.  RENAME the file to an extension other than .EXE or .HEX.
                  Back up the file first if appropriate.

              2.  Load the file into memory using the DEBUG or Load command.

              3.  Modify the file as needed in memory, but do not try to
                  execute it with the Go or Trace commands. Unpredictable
                  results would occur.

              4.  Write the file back using the Write command.

              5.  RENAME the file to its correct name.