Phoenix CD 2.0/Phoenix_CD.cdr/11a/diskprep.zip/DISKPREP.DOC

Text File | 1987-04-23 | 10KB | 182 lines

     From PC-Magazine Volume 5, Number 21, December 9, 1986
     PROGRAMMING/UTILITIES, Jeff Prosise, pages 303-324

     RETROFITTING A DOS SYSTEM

     Every time you get out a new floppy disk, you face the choice of
     whether to format it with or without the DOS system files.  Having the
     system on the disk is often handy, especially at boot time or when the
     transient portion of COMMAND.COM gets overlayed.  But space is
     precious on a 360K disk, and the two hidden system files, together
     with the command processor COMMAND.COM, eat up almost 40K of that
     space in DOS 2.1, 68K in DOS 3.2.

     Inevitably, you occasionally leave off the system files only to wish
     later that you hadn't.  The DOS SYS command doesn't help at this
     point, since it can add a system only if the disk is blank or if
     certain critical areas of the disk were initially reserved by using
     the FORMAT/B option.  Of course, if you'd had the foresight to reserve
     the space, you'd have installed the system to begin with.  (The /B
     switch was included with DOS simply so that non-IBM software vendors,
     who could not legally sell disks with copyrighted system files
     included, could reserve room for users to add the system after
     purchase.)  Usually, your only recourse is to format a fresh disk with
     FORMAT/S and copy everything from the old disk onto the new one.

     DISKPREP.COM provides a better solution.  DISKPREP rearranges the data
     clusters, the file allocation table, and the directory of a nonsystem
     disk so that the SYS command will successfully add the system even if
     some of the disk files presently occupy territory needed by the
     system files.  It also lets you delete existing system files and
     replace them with more current ones.

     Transforming a nonsystem disk into a system disk is a three-step
     process that begins by preparing the disk with DISKPREP.  The syntax
     for DISKPREP is simply

          DISKPREP [d:]

     where d: is an optional drive specifier for use if the target disk is
     not in the default drive.  Up to 44K of free disk space, depending on
     the version of DOS you use, are required for SYS.COM to add the two
     hidden system files.  In addition, at least two entries in your disk's
     root directory must be unused.

     If DISKPREP finds that your disk has less than adequate space, it will
     abort with a message indicating as much.  If that happens, delete one
     or more files to free up some room and try again.  If the disk your're
     prepping is already system formatted, the program will display the
     message "System already installed - Delete old system (Y/N)?" and
     await your keypress.  If you respond with a Y, the old system will be
     erased; if you answer N, execution will terminate harmlessly.  In the
     unlikely event that DISKPREP encounters an error condition such as a
     lost cluster when traversing an allocation chain, it will abort with
     an "Allocation chain error" message and leave you to your own devices.
     Another possible but unlikely occurrence is that DISKPREP will find
     one or more bad sectors in the area of the disk where the system is to
     be installed.  If that happens, the message "Bad sector in system
     area" is issued and execution is aborted.

     Once DISKPREP has finished, you use the SYS.COM program supplied with
     DOS to install the system on the disk.  This simply involves copying a
     pair of hidden system files from one disk to another and ensuring that
     they occupy certain areas in the directory and the data space.
     Fortunately, SYS takes care of that task.  SYS's syntax is almost
     identical to that of DISKPREP and is detailed in your DOS manual.
     Note that if you try to use the disk after DISKPREPing but before
     SYStemizing, DOS will think that it's dealing with a newly formatted
     disk and will respond to a DIR request with a "File not found"
     message.  Likewise, using CHKDSK to analyze a disk that has been
     prepared but not yet SYStemized may produce some strange results.
     Have faith: as soon as SYS.COM is run, your files will reappear intact
     and the disk will be ready for use again.

     The final step in transforming your disk into a complete system disk
     is to copy the file COMMAND.COM from your DOS disk to the target disk.
     This is necessary because, unlike FORMAT/S, SYS does not automatically
     add COMMAND.COM for you.  You simply use the DOS COPY command to
     perform the transfer.

     The three steps involved in the SYStemization process are natural
     candidates for a batch file, and to facilitate just that use, DISKPREP
     terminates with a return code that can be read by the conditional
     parameter ERRORLEVEL.  If the disk prepping process was successful,
     ERRORLEVEL is set to zero.  If the prepping process was not
     successful for any reason, DISKPREP executes its normal abort routine
     complete with a message revealing the nature of the error and sets the
     ERRORLEVEL return code to 1.  A suitable batch file (you might call it
     SYSTEM.BAT) is listed below.  It assumes that the program disk is in
     the default drive and that the target disk is in drive B:

          DISKPREP B:
          IF ERRORLEVEL 1 GOTO END
          SYS B:
          COPY COMMAND.COM B:
          :END

     DISKPREP works on floppy disks of the 40-track variety with one or two
     sides and eight or nine sectors per track.  This covers all four 5 1/4
     inch disk formats supported by versions of DOS prior to 3.0 but
     excludes hard disks, high-capacity (1.2-meg) floppies like those used
     by the AT, and the 3 1/2 inch disk cartridges used by a number of
     laptop portables.  Attempting to process one of the latter types of
     disks isn't harmful: the program will quickly recognize the
     unsupported format and abort with an "Illegal disk format" message.

     Two cautions are in order.  First, do not use DISKPREP on a disk that
     contains subdirectories.  While sometimes subdirectories will not
     interfere with the reallocation process, at other times their presence
     may cause an "Allocation chain error" message, prevent existing system
     files from being deleted (resulting in the error message "Cannot
     delete system files"), or result in a damaged file allocation table.
     Fortunately, there's little use for tree-structured directories on a
     floppy, anyway, so this limitation is not too serious.  Second, it's
     risky to try to prep a copy-protected disk, since many copy protection
     schemes alter the disk format.  DISKPREP should work with any current
     release of DOS but may or may not be compatible with future versions.

     If you run SYS.COM on a nonsystem disk that isn't empty without
     first running DISKPREP, SYS will usually respond with a "No room for
     system on destination disk" message.  In some cases, however, SYS may
     appear to add the files successfully, though you'll find that the disk
     won't boot even though SYS apparently succeeded.  So, check any disk
     you SYStemize by booting your PC with it.  If you have a disk with an
     improperly installed system, DISKPREP can be used to correct it.  The
     program's ability to delete system files works just as well with a
     faulty system as with one added properly.  Even DISKPREP will
     sometimes fail if you delete a system installed under DOS 3.1 and
     resystemized with the DOS 2.1 version of SYS.  If you encounter this
     problem, don't dispair; DISKPREPing the disk a second time and running
     DOS 3.1 SYS will restore it unharmed.  There seems to be no problems
     with replacing system files with a system of the same version of DOS
     or later, which is the normal requirement.

     DISKPREP begins by parsing the command line for a drive specifier.
     If no drive is specified, DISKPREP uses DOS function call 19h to get
     the default drive and thereafter uses the default as the target drive.
     The drive identifier, whether input explicitly or by default, is
     checked, and execution terminates if comething other than drive A: or
     B: is specified.  This provides one measure of assurance that DISKPREP
     won't try to reallocate space on a hard disk.

     Be aware that any program, no matter how extensive its testing and
     use, may fall prey to hidden bugs or anomalies.  [One user has
     cautioned that ProKey should not be loaded in advance of using
     DISKPREP, for example.]  It's always prudent to keep backup copies of
     important files and disks.  But when you need to add a system to a
     disk in use, DISKPREP's the easy way to go.




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