Informática Multimedia 1995 April

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Text File | 1991-06-24 | 13.9 KB | 268 lines

README.DOC File Safe Erase Version 1.61 (C) Copyright by Tom Williams, 1990-1991 Safe Erase version 1.61 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. Safe Erase also will work fine with 4DOS, the command.com replacement. (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.) (4DOS is a trademark of J.P. Software.) 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. 4DOS users will find it very easy to type in erase and del and have killf.exe activated as a result. 4DOS users can use the ALIAS command to achieve this. 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 small Safe File Table on your disk. This is automatically done when the KILLF command is used for the first time on a particular disk. Once the Safe File Table is built, the KILLF command will recognize that it's there the next time it is used to erase a file on that disk. The KILLF command will only build a new Safe File Table on disks that don't have one already. The table is a read-only file. Now when you erase a file using KILLF the first thing that gets done is that the file's cluster numbers get stored in the Safe File Table. Then the file's cluster numbers are removed from the MS-DOS file allocation table. Now the file is erased but its cluster numbers are stored in the Safe File Table. Now if it is decided that the file is really needed or not the intended file to be deleted, the user can simply retrieve the file by typing RETRIEVE in the directory of the deleted file. Safe File Retrieve has a simple task of retrieving the file since its cluster numbers are stored in the Safe File Table. It is a simple procedure to begin using the Safe Erase package. Please read the file install.doc to learn how to begin using the Safe Erase package. The Safe Erase software package consists of the following 6 files: 1) readme.doc - Introduction to Safe Erase and what it offers. 2) install.doc - Instructions for setting up Safe Erase and how to use it. 3) killf.exe - Used to erase files safely instead of erase or del. 4) retrieve.exe - Safe File Retrieve program used to retrieve erased files. 5) buildtab.exe - Puts a Safe File Table on a disk for safe file erasing. 6) killtab.exe - Used to erase a read-only Safe File Table. SHAREWARE NOTICE ---------------- Shareware: Please help distribute Safe Erase by sharing unmodified copies of the software package. Please upload Safe Erase to computer bulletin board systems. Safe Erase Version 2.00 will be available on July 1, 1991. Version 2.00 will allow the user to remove a subdirectory with the Safe Erase command KILLD and have the directory's cluster numbers stored in the Safe File Table in the same way that Version 1.61 stores a file's cluster numbers. This will give the user a 100% recovery success rate if files or subdirectories are erased. If you use Safe Erase version 1.61 please support it by becoming a registered user at a cost of $15. A registered user is entitled to the following benefits: o One upgrade of Safe Erase, version 2.00 or later shipped by mail. o A copy of Safe Erase with your own registration number. Let anyone interested make a copy of your registered version and if they register you get a $5 commission. Your registered copy of Safe Erase could get passed around for years to come. Because of the real need for Safe Erase and its popularity, registered users who share the package could find commission checks trickling in for years to come. To register send a check to: Tom Williams P.O. Box 563 Fayetteville, New York 13066 Please include registration number 0008703 when sending the check to credit the person that shared this copy of Safe Erase. Please also specify 5.25 inch diskettes or 3.5 inch diskettes. ----------------end-of-author's-documentation--------------- Software Library Information: This disk copy provided as a service of Public (software) Library We are not the authors of this program, nor are we associated with the author in any way other than as a distributor of the program in accordance with the author's terms of distribution. Please direct shareware payments and specific questions about this program to the author of the program, whose name appears elsewhere in this documentation. If you have trouble getting in touch with the author, we will do whatever we can to help you with your questions. All programs have been tested and do run. To report problems, please use the form that is in the file PROBLEM.DOC on many of our disks or in other written for- mat with screen printouts, if possible. PsL cannot debug pro- programs over the telephone, though we can answer questions. 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