GDISK v1.0f-BETA is the second Beta release of the GDISK product. We have received a lot of feedback from users after GDISK 1.0e was released and have now modified the product in response to those suggestions. The following list details the changes made to GDISK since the previous Beta release:

• In the default display mode (/STATUS), GDISK displays a list of all installed fixed disks if no fixed disk number is specified.
• A new /WIPE switch may be used in conjunction with the /MBR switch which will cause all existing partitions to be deleted when the Master Boot Record is reinitialized.
• Error messages reporting failures to read, write, or verify sectors on disk now also identify the fixed disk on which the error was encountered.
• Compaq diagnostic partitions are recognized and displayed in the list of partitions in the same order as they are displayed by FDISK.
• For newly installed fixed disks that do not yet have a Master Boot Record, the MBR is initialized automatically when the first partition is created to match the behavior of FDISK.
• And lastly, the most popular request: Logical DOS drives may now be hidden and unhidden.

GDISK is intended as a complete replacement for the DOS/Windows 95 FDISK utility. Everything you can do with FDISK you can do with GDISK. The partitions created with GDISK are indistinguishable from those created using FDISK.

GDISK is command-line driven – unlike FDISK which uses interactive menus and prompts – so it is much quicker for configuring a disk’s partition table and does a few extra things that FDISK does not.

GDISK has six main modes of operation, the first four of which correspond to the menu options in FDISK’s main menu.

1. Creating partitions - Primary DOS partitions, Extended DOS partitions, Logical DOS drives.
2. Deleting partitions of any type, including Non-DOS partitions.
3. Listing current partition information and installed fixed disks.
4. Activating a partition (nominating it as the bootable partition).
5. Making existing partitions invisible and visible again.
6. Reinitializing the Master Boot Record.

GDISK provides some added capabilities that FDISK does not – such as on-the-fly formatting – and provides a safer alternative in situations where known problems with FDISK can cause data loss and hardware damage.

1. Command-line driven and much quicker than FDISK. Allows standard configurations to be defined in a batch file and applied to multiple computers.
2. Gives better disk space utilization. It is much more aggressive in finding free space on the disk for new partitions, and in virtually every case will find space ignored by FDISK (this space can vary between 0.5MB and 16MB). Alternatively the /-CE switch may be specified when creating partitions to force FDISK-compatibility.
3. Reduces slack space (disk wastage). GDISK is more aggressive than the FORMAT utility provided with Windows 95 in attempting to keep cluster sizes small. For some partition sizes, GDISK is able to format partitions with cluster sizes half the size that FORMAT would select resulting in an effective 10-35% increase in drive capacity.
4. Allows partitions to be hidden. This can be used to have more than one Primary DOS partition with different versions of DOS/Windows 95 in each partition. Normally it is not possible to have more than one DOS or Windows 95 installation on the same computer. The ability to hide partitions allows the computer to be used to boot into any selected bootable partition ignoring other installations of the same operating system in other partitions.
5. The FDISK supplied with Windows 95 has a bug that can cause overlapping partitions to be created that will almost certainly lead to corruption of existing partitions. The same bug can also result in partitions that extend past the end of the disk, which can cause permanent damage to the drive when the partition is formatted. This is the one situation in which GDISK does not imitate the exact behavior of FDISK – even with the compatibility switch turned on.
6. The FDISK supplied with Windows 95 has a bug that means that it is not possible to delete newly created partitions if the drive letter that was provisionally assigned to the new drive matches a drive letter currently assigned to a CD-ROM device. GDISK allows the partitions to be deleted even if the new drive letter is currently assigned.
7. Useful as a diagnostic tool – extensive integrity verification checks are performed on the partition tables before any operations are performed on the drive.
8. GDISK can display the partition information in a raw cylinder/head/sector format that may be of use to technicians investigating problems with a computer's partition table.

GDISK has five main modes of operation – creating partitions, deleting partitions, displaying partition information, activating partitions, and hiding partitions. The mode that GDISK operates in is denoted by the switches /CRE, /DEL, /STATUS (the default), /ACT, and /HIDE.

An overview of these modes and their switches may be displayed by using the help switch as follows:

An additional switch not shown here in the help text is the /VERSION switch which displays the version information for the GDISK executable.

More detailed help may be accessed by qualifying the help request with the switch for one of the modes:

C:\> GDISK /? /CRE
Creates fixed disk partitions and logical drives.

GDISK disk /CRE {/PRI|/EXT|/LOG} [/SZ:mbytes] [/FOR [/Q] [/V[:label]]]
      [/-32] [/-CE] [/X] [/Y]

  disk         The physical fixed disk (1-8).
  /CRE         Create a DOS partition or logical DOS drive.
  /PRI         Create a primary DOS partition.
  /EXT         Create an extended DOS partition.
  /LOG         Create a logical DOS drive in the extended DOS
               partition.
  /SZ:mbytes   Specifies the size of the partition. Default is to
               create a partition of the largest possible size.
  /FOR         Format the new partition once it has been created.
  /Q           Perform a quick format on the new partition.
  /V[:label]   Specifies the volume label. Default is no label.
  /-32         Ignore large-disk support (FAT32). Limits maximum size
               of new primary DOS partitions and logical DOS drives to
               2048 MB.
  /-CE         Ignore any free space in the Customer Engineering (CE)
               cylinder.
  /X           Ignore extended disk-access support.
  /Y           Suppress prompting to confirm you wish the action to be
               performed. /SURE has the same meaning.

The /MBR switch may be used to rewrite the boot code in the Master Boot Record. The usual reason for needing to reinitialize the MBR is to eliminate a boot sector virus residing there.

Reinitializing the Master Boot Record does not alter the disk's partition information but can be destructive if other software has replaced the original standard Master Boot Record. This will be the case if a disk extender (such as OnTrack's DiskManager) or operating system loader (such as OS/2's Boot Manager) have been installed.

Warning: Do not use the /MBR switch if a disk extender is installed as it will render the partition data inaccessible until the extender has been reinstalled.

Another situation in which the /MBR switch may be useful relates to a bug in some BIOSes: if a new disk is installed or a different operating system loaded, the next time an IDE auto-detect is performed in the BIOS some devices may fail to be detected. It may be that the new drive itself, the primary drive containing the new operating system, or other IDE devices such as a CD-ROMs are the ones that cannot be detected by the BIOS. Using GDISK /MBR on each of the disk's will often repair this problem.

This version of GDISK contains extensive internal self-checks in the form of logical assertions. In the final release of the product these checks will be turned off. In this pre-release version these checks enable us to double-check the internal behavior of the program.

Literally hundreds of these checks are made each time that GDISK is executed. If any of these checks fail, an assertion failure message is displayed that will look similar to the following:

Assertion failed: example_assertion == false, file GDISK.CPP, line 159
Abnormal program termination

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