Collection of Tools & Utilities/Collection of Tools and Utilities.iso/dskut/safera16.zip/README.DOC

Text File | 1991-06-21 | 12KB | 214 lines

                             README.DOC File

                         Safe Erase Version 1.60

                   (C) Copyright by Tom Williams, 1990-1991

Safe Erase version 1.60 is a new shareware utility that offers a
preferred alternative to the MS-DOS ERASE, DEL, and UNDELETE commands.
Safe Erase provides a new erase command that enhances the erase
procedure so that erased files are 100% recoverable with the Safe Erase
Retrieve program.  Before MS-DOS 5.0, Safe Erase was the only utility
that could ensure that any files that got erased could be retrieved at a
100% success rate.  MS-DOS 5.0 offers its new file deletion-tracking
function which is an approach to 100% recoverability that is very
similar to Safe Erase.  Safe Erase, however, is still very easily the
preferred alternative to this new MS-DOS 5.0 function.

Safe Erase has many advantages over the MS-DOS file deletion-tracking
method.  Both programs use a file to store the allocated clusters of
files just before they are erased.  The problem with the MS-DOS 5.0
method is that it will build a huge file when told that many files will
be erased.  This file will store the names and allocated clusters of
files erased by the next ERASE or DEL command that takes place.
Actually, MS-DOS 5.0 builds three files, two of which are very large.
Safe Erase builds only one file the same size as the File Allocation
Table for that particular disk or diskette, which takes up much less
disk space than the deletion-tracking file that MS-DOS 5.0 builds.  The
following example compares the disk space required by each method to
track the deletion of 999 files.  On a diskette with 1,457,664 bytes
total disk space MS-DOS 5.0 builds a hidden file called PCTRACKR.DEL
that takes up 181,822 bytes.  It also builds a file called MIRROR.FIL
that takes up 13,312 bytes for a total of 195,134 bytes.  Safe Erase
requires only 4,608 bytes of disk space to build its Safe File Table.
Safe Erase needs only two percent of the disk space that MS-DOS requires
in this example.

Another big problem with the deletion-tracking method is that MS-DOS
requires you to tell it how many deleted files to be prepared for,
otherwise it defaults to a small number.  If you tell it 100 and then
erase 125 files with a command such as ERASE *.*, the MS-DOS UNDELETE
program will only be able to retrieve the first 100 files.  This is how
the deletion-tracking file gets so large, the more files you tell it to
be prepared for the larger the deletion-tracking file it builds.  The
Safe File Table that Safe Erase builds will always stay the same size
for a particular disk or diskette.  It doesn't matter how many files you
delete, the table will never need to grow for that particular disk.
Also, 999 files is the maximum number that the deletion-tracking method
can handle.  Safe Erase is prepared for an erasure of any number of
files, even directories with thousands of files.  Safe Erase does not
need to be given a number of deleted files to be prepared for.  It is
prepared for any number of deleted files.

The third big problem with the deletion-tracking method is that when you
tell MS-DOS to build its deletion-tracking file, it builds it as a
hidden file and it makes you really unsure if the file was created or
not.  Safe Erase builds its Safe File Table as a read-only file that is
visible with the DIR command so you know that you have successfully
created a Safe File Table.

The fourth big advantage that Safe Erase has over the DOS deletion-
tracking method is that Safe Erase will automatically build a Safe File
Table on a disk that does not have one before it erases any files.  The
fifth advantage of Safe Erase is that it does not operate as a memory
resident program like the deletion-tracking method, so Safe Erase saves
you valuable RAM.  The sixth and largest advantage of the Safe Erase
method is that Safe Erase version 2.00 (available July 1, 1991) will
offer the same protection for erased subdirectories as it now does for
files.  MS-DOS 5.0 does not deliver this function with its deletion-
tracking method.


          Note:  Safe Erase version 2.00 also will offer the
          very special feature of already knowing the first
          character of each erased file's name.  Just by
          pressing F5 all files will be retrieved without you
          having to know and type in the first characters of
          the erased file names.  The Norton Utilities can't
          do this.  Safe Erase is simply the very best file
          retrieval method available!


Safe Erase will work fine on all systems with MS-DOS versions 2.10 and
higher.

(MS-DOS is a registered trademark of Microsoft Corporation.)
(UNDELETE Copyright (C) 1987-1991 Central Point Software, Inc.)
(Norton Utilities is a trademark of Peter Norton.)

Other software utilities that recover erased files can usually retrieve
most files but many times there are files that cannot be retrieved even
when no new files have been put out on the disk after the erasure.  The
new Safe File RETRIEVE program easily retrieves any files that have been
erased with the Safe Erase KILLF command.  The KILLF.EXE file can be
personalized or renamed to anything you like such as killfile.exe or
mydel.exe, using the DOS RENAME command.  Do not rename killf.exe to be
erase.exe or del.exe.  MS-DOS will think you are trying to use its
internal erase or del command and never call your version of the erase
or del command.

NOTE:  If you're really addicted to typing erase or del when erasing
files request the Safe Erase Install program when registering for Safe
Erase version 2.00.  The Safe Erase Install program will allow you to
use the Safe Erase programs erase.exe and del.exe.  These programs work
the same as killf.exe but are not shipped with Safe Erase version 2.00
unless requested.  The Safe Erase Install program works by replacing 4
bytes in your command.com file.  The patch tells MS-DOS to let you run
the Safe Erase programs named erase.exe, del.exe, rmdir.exe, and rd.exe
instead of the erase, del, rmdir, and rd commands that are internal to
MS-DOS.  Rmdir.exe and rd.exe work exactly like the killd.exe program
that comes with Safe Erase version 2.00.  The Safe Erase Install program
comes with a companion program called De-install that will remove the
patch from your command.com file if you no longer want to use Safe
Erase.  So using the Install patch program is completely harmless.  Once
again, these programs are only shipped with version 2.00 if requested.

The Safe Erase KILLF command is smart enough to know which version of
MS-DOS you are using and will work the same way erase and del have for
your version of DOS.  KILLF can do everything functionally that the MS-
DOS erase and del commands can do.  KILLF can be used at the command
prompt or in batch programs.  Safe Erase works with disks of any size.
Files can be retrieved on disks with partitions greater than 32 mega-
bytes.  KILLF and RETRIEVE will work fine on RAM disks created with
VDISK.SYS and RAMDRIVE.SYS.



                          How Safe Erase Works
                          --------------------

Understanding how Safe Erase works is much easier after a quick
explanation of what the existing MS-DOS erase and del commands do to
erase a file.  When the user erases a file MS-DOS changes the first
character of the file name to the "σ" character and then removes all the
file's cluster numbers from the file allocation table.  When conven-
tional file recovery programs attempt to recover a file, they often must
make a best guess of which available clusters belong to your file.  This
is why sometimes you think you have recovered a file and then you find
that it has some bad data in it.  Safe Erase takes a completely new
approach to file recovery.  Conventional file recovery programs use a
pound of cure in attempting to retrieve erased files.  Safe Erase uses
an ounce of prevention when files are erased so that they can be easily
and accurately retrieved if needed.

Safe Erase works by building a sm